# Arthropod

> Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Arthropod
> Markdown URL: https://mediated.wiki/source/Arthropod.md
> Source: https://en.wikipedia.org/wiki/Arthropod
> Source revision: 1355507261
> License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/)

Not to be confused with [Anthropod](/source/Anthropod_(disambiguation)) or [Anthropoid](/source/Anthropoid_(disambiguation)).

**Arthropods** (/ˈɑːrθrəˌpɒd/ AR-thrə-pod)[3][4] are [invertebrates](/source/Invertebrate) in the [phylum](/source/Phylum) **Arthropoda**. They possess an [exoskeleton](/source/Arthropod_exoskeleton) with a [cuticle](/source/Cuticle) made of [chitin](/source/Chitin), often [mineralised](/source/Mineralization_(biology)) with [calcium carbonate](/source/Calcium_carbonate), a body with differentiated ([metameric](/source/Metamerism_(biology))) [segments](/source/Segmentation_(biology)), and paired jointed [appendages](/source/Appendage). In order to keep growing, they must go through stages of [moulting](/source/Moulting), a process by which they shed their exoskeleton to reveal a new one. They form an extremely diverse group of up to ten million species.

[Haemolymph](/source/Haemolymph) is the analogue of [blood](/source/Blood) for most arthropods. An arthropod has an [open circulatory system](/source/Open_circulatory_system), with a body cavity called a [haemocoel](/source/Haemocoel) through which haemolymph circulates to the interior [organs](/source/Organ_(anatomy)). Like their exteriors, the internal organs of arthropods are generally built of repeated segments. They have ladder-like [nervous systems](/source/Nervous_system), with paired [ventral](/source/Anatomical_terms_of_location#Dorsal_and_ventral) [nerve cords](/source/Ventral_nerve_cord) running through all segments and forming paired [ganglia](/source/Ganglia) in each segment. Their heads are formed by fusion of varying numbers of segments, and their [brains](/source/Brain) are formed by fusion of the ganglia of these segments and encircle the [esophagus](/source/Esophagus). The [respiratory](/source/Respiratory_system) and [excretory](/source/Excretion) systems of arthropods vary, depending as much on their environment as on the [subphylum](/source/Subphylum) to which they belong.

Arthropods use combinations of [compound eyes](/source/Compound_eye) and [pigment-pit ocelli](/source/Simple_eye_in_invertebrates) for vision. In most species, the ocelli can only detect the direction from which light is coming, and [the compound eyes](/source/Arthropod_eye) are the main source of information; however, in [spiders](/source/Spider), the main eyes are ocelli that can form images and, in a few cases, can swivel to track prey. Arthropods also have a wide range of chemical and mechanical sensors, mostly based on modifications of the many bristles known as [setae](/source/Seta) that project through their cuticles. Similarly, their reproduction and development are varied; all [terrestrial](/source/Terrestrial_animal) species use [internal fertilization](/source/Internal_fertilization), but this is sometimes by indirect transfer of the [sperm](/source/Sperm) via an appendage or the ground, rather than by direct injection. Aquatic species use either internal or [external fertilization](/source/External_fertilization). Almost all arthropods lay eggs, with many species giving birth to live young after the eggs have hatched inside the mother. Still, a few are genuinely [viviparous](/source/Viviparity), such as [aphids](/source/Aphid). Arthropod hatchlings vary from miniature adults to grubs and [caterpillars](/source/Caterpillar) that lack jointed limbs and eventually undergo a total [metamorphosis](/source/Metamorphosis) to produce the adult form. The level of maternal care for hatchlings varies from nonexistent to the prolonged care provided by [social insects](/source/Eusociality#In_insects).

The evolutionary ancestry of arthropods dates back to the [Cambrian](/source/Cambrian) period. The group is generally regarded as [monophyletic](/source/Monophyletic), and many analyses support the placement of arthropods with [cycloneuralians](/source/Cycloneuralia) (or their constituent clades) in a superphylum [Ecdysozoa](/source/Ecdysozoa). Overall, however, the [basal](/source/Basal_(evolution)) relationships of animals are not yet well resolved. Likewise, the relationships between various arthropod groups are still actively debated. Today, arthropods contribute to the human food supply both directly as food and more importantly, indirectly as [pollinators](/source/Pollination) of crops. Some species are known to spread severe disease to humans, livestock, and crops.

## Etymology

The word *arthropod* comes from the [Greek](/source/Greek_language) ἄρθρον *árthron* '[joint](/source/Joint)', and πούς *poús* ([gen.](/source/Genitive) ποδός *podós*) '[foot](/source/Foot)' or '[leg](/source/Leg)', which together mean "jointed leg",[5] with the word "arthropodes" initially used in anatomical descriptions by [Barthélemy Charles Joseph Dumortier](/source/Barth%C3%A9lemy_Charles_Joseph_Dumortier) published in 1832.[1] The designation "Arthropoda" appears to have been first used in 1843 by the German zoologist [Johann Ludwig Christian Gravenhorst](/source/Johann_Ludwig_Christian_Gravenhorst) (1777–1857).[6][1] The origin of the name has been the subject of considerable confusion, with credit often given erroneously to [Pierre André Latreille](/source/Pierre_Andr%C3%A9_Latreille) or [Karl Theodor Ernst von Siebold](/source/Karl_Theodor_Ernst_von_Siebold) instead, among various others.[1]

Terrestrial arthropods are often called bugs.[Note 1] The term is also occasionally extended to colloquial names for freshwater or marine [crustaceans](/source/Crustacean) (e.g., [Balmain bug](/source/Balmain_bug), [Moreton Bay bug](/source/Moreton_Bay_bug), [mudbug](/source/Mudbug)) and used by physicians and bacteriologists for disease-causing germs (e.g., [superbugs](/source/Antimicrobial_resistance)),[7] but entomologists reserve this term for a narrow category of "[true bugs](/source/True_bugs)", insects of the order [Hemiptera](/source/Hemiptera).[7]

## Description

Arthropods are [invertebrates](/source/Invertebrate) with [segmented](/source/Segmentation_(biology)) bodies and jointed limbs.[8] The [exoskeleton](/source/Exoskeleton) or [cuticle](/source/Arthropod_cuticle) consists of [chitin](/source/Chitin), a polymer of [N-Acetylglucosamine](/source/N-Acetylglucosamine).[9] The cuticle of many crustaceans, [beetle mites](/source/Oribatida), the clades Penetini and Archaeoglenini inside the beetle subfamily [Phrenapatinae](/source/Phrenapatinae),[10] and millipedes (except for [bristly millipedes](/source/Polyxenida)) is also [biomineralized](/source/Biomineralization) with [calcium carbonate](/source/Calcium_carbonate). Calcification of the endosternite, an internal structure used for muscle attachments, also occurs in some [opiliones](/source/Opiliones),[11] and the pupal cuticle of the fly *[Bactrocera dorsalis](/source/Bactrocera_dorsalis)* contains calcium phosphate.[12]

### Diversity

Arthropoda is the largest animal [phylum](/source/Phylum), with the estimates of the number of arthropod species varying from 1,170,000 to 5~10 million and accounting for over 80 percent of all known living animal species.[13][14] One arthropod sub-group, the [insects](/source/Insect), includes more [described species](/source/Species_description) than any other [taxonomic class](/source/Class_(biology)).[15] The total number of species remains difficult to determine, as estimates rely on census counts at specific locations, scaled up and projected onto other regions, then totalled – allowing for double-counting – to cover the whole world. Modeling assumptions are involved at each stage, introducing uncertainty. A study in 1992 estimated that there were 500,000 species of animals and plants in [Costa Rica](/source/Costa_Rica) alone, of which 365,000 were arthropods.[15]

They are important members of marine, freshwater, land and air [ecosystems](/source/Ecosystem) and one of only two major animal groups that have adapted to life in dry environments; the other is [amniotes](/source/Amniote), whose living members are reptiles, birds and mammals.[16] Both the smallest and largest arthropods are [crustaceans](/source/Crustacean). The [smallest](/source/Smallest_organisms#Arthropods_(Arthropoda)) belong to the class [Tantulocarida](/source/Tantulocarida), some of which are less than 100 micrometres (0.0039 in) long.[17] The [largest](/source/Largest_and_heaviest_animals#Arthropods_(Arthropoda)) are species in the class [Malacostraca](/source/Malacostraca), with the legs of the [Japanese spider crab](/source/Japanese_spider_crab) potentially spanning up to 4 metres (13 ft)[18] and the [American lobster](/source/American_lobster) reaching weights over 20 kg (44 lbs).

### Segmentation

The [embryos](/source/Embryo) of all arthropods are segmented, consisting of a series of repeated modules. The [last common ancestor](/source/Most_recent_common_ancestor) of living arthropods probably consisted of a series of undifferentiated segments, each with a pair of [appendages](/source/Appendage) that functioned as limbs. However, all known living and fossil arthropods have grouped segments into [tagmata](/source/Tagma_(biology)) in which segments and their limbs are specialized in various ways.[16]

The three-part appearance of many [insect](/source/Insect) bodies and the two-part appearance of [spiders](/source/Spider) is a result of this grouping.[19] There are no external signs of segmentation in [mites](/source/Mite).[16] Arthropods also have two body elements that are not part of this serially repeated pattern of segments, an [ocular somite](/source/Somite) at the front, where the mouth and eyes originated,[16][20] and a [telson](/source/Telson) at the rear, behind the [anus](/source/Anus).

Originally, it seems that each appendage-bearing segment had two separate pairs of appendages: an upper, unsegmented [exite](/source/Exite) and a lower, segmented endopod. These would later fuse into a single pair of [biramous](/source/Biramous) appendages united by a basal segment (protopod or basipod), with the upper branch acting as a [gill](/source/Gill) while the lower branch was used for locomotion.[21][22][23] The appendages of most [crustaceans](/source/Crustaceans) and some extinct taxa such as [trilobites](/source/Trilobites) have another segmented branch known as [exopods](/source/Exopod), but whether these structures have a single origin remain controversial.[24][25][23] In some segments of all known arthropods, the appendages have been modified, for example to form gills, mouth-parts, [antennae](/source/Antenna_(biology)) for collecting information,[19] or claws for grasping;[26] arthropods are "like [Swiss Army knives](/source/Swiss_Army_knife), each equipped with a unique set of specialized tools."[16] In many arthropods, appendages have vanished from some regions of the body; it is particularly common for abdominal appendages to have disappeared or be highly modified.[16]

The most conspicuous specialization of segments is in the head. The four major groups of arthropods – [Chelicerata](/source/Chelicerata) ([sea spiders](/source/Sea_spider), [horseshoe crabs](/source/Horseshoe_crab) and [arachnids](/source/Arachnid)), [Myriapoda](/source/Myriapoda) ([symphylans](/source/Symphylan), [pauropods](/source/Pauropod), [millipedes](/source/Millipede) and [centipedes](/source/Centipede)), [Pancrustacea](/source/Pancrustacea) ([oligostracans](/source/Oligostracan), [copepods](/source/Copepod), [malacostracans](/source/Malacostracan), [branchiopods](/source/Branchiopod), [hexapods](/source/Hexapoda), etc.), and the extinct [Trilobita](/source/Trilobita) – have heads formed of various combinations of segments, with appendages that are missing or specialized in different ways.[16][27] Despite myriapods and hexapods both having similar head combinations, hexapods are deeply nested within crustacea while myriapods are not, so these traits are believed to have evolved separately. In addition, some extinct arthropods, such as *[Marrella](/source/Marrella)*, belong to none of these groups, as their heads are formed by their own particular combinations of segments and specialized appendages.[28]

Working out the evolutionary stages by which all these different combinations could have appeared is so difficult that it has long been known as "The [arthropod head problem](/source/Arthropod_head_problem)".[29] In 1960, R. E. Snodgrass even hoped it would not be solved, as he found trying to work out solutions to be fun.[Note 2]

### Exoskeleton

Main article: [Arthropod exoskeleton](/source/Arthropod_exoskeleton)

Arthropod exoskeletons are made of [cuticle](/source/Arthropod_cuticle), a non-cellular material secreted by the [epidermis](/source/Epidermis_(zoology)).[16] Their cuticles vary in the details of their structure, but generally consist of three main layers: the [epicuticle](/source/Epicuticle), a thin outer [waxy](/source/Wax) coat that moisture-proofs the other layers and gives them some protection; the [exocuticle](/source/Exocuticle), which consists of [chitin](/source/Chitin) and chemically hardened [proteins](/source/Protein); and the [endocuticle](/source/Endocuticle), which consists of chitin and unhardened proteins. The exocuticle and endocuticle together are known as the [procuticle](/source/Procuticle).[30] Each body segment and limb section is encased in hardened cuticle. The joints between body segments and between limb sections are covered by flexible cuticle.[16]

The exoskeletons of most aquatic [crustaceans](/source/Crustacean) are [biomineralized](/source/Biomineralization) with [calcium carbonate](/source/Calcium_carbonate) extracted from the water. Some terrestrial crustaceans have developed means of storing the mineral, since on land they cannot rely on a steady supply of dissolved calcium carbonate.[31] Biomineralization generally affects the exocuticle and the outer part of the endocuticle.[30] Two recent hypotheses about the evolution of biomineralization in arthropods and other groups of animals propose that it provides tougher defensive armor,[32] and that it allows animals to grow larger and stronger by providing more rigid skeletons;[33] and in either case a mineral-organic [composite](/source/Composite_material) exoskeleton is cheaper to build than an all-organic one of comparable strength.[33][34]

The cuticle may have [setae](/source/Seta) (bristles) growing from special cells in the epidermis. Setae are as varied in form and function as appendages. For example, they are often used as sensors to detect air or water currents, or contact with objects; aquatic arthropods use [feather](/source/Feather)-like setae to increase the surface area of swimming appendages and to [filter](/source/Filter_feeding) food particles out of water; aquatic insects, which are air-breathers, use thick [felt](/source/Felt)-like coats of setae to trap air, extending the time they can spend under water; heavy, rigid setae serve as defensive spines.[16]

Although all arthropods use muscles attached to the inside of the exoskeleton to flex their limbs, some still use [hydraulic](/source/Hydraulic) pressure to extend them, a system inherited from their pre-arthropod ancestors;[35] for example, all spiders extend their legs hydraulically and can generate pressures up to eight times their resting level.[36]

### Moulting

Main article: [Ecdysis](/source/Ecdysis)

The exoskeleton cannot stretch and thus restricts growth. Arthropods, therefore, replace their exoskeletons by undergoing [ecdysis](/source/Ecdysis) (moulting), or shedding the old exoskeleton, the [exuviae](/source/Exuviae), after growing a new one that is not yet hardened. Moulting cycles run nearly continuously until an arthropod reaches full size. The developmental stages between each moult (ecdysis) until sexual maturity is reached is called an [instar](/source/Instar). Differences between instars can often be seen in altered body proportions, colors, patterns, changes in the number of body segments or head width. After moulting, i.e. shedding their exoskeleton, the juvenile arthropods continue in their life cycle until they either pupate or moult again.[37]

In the initial phase of moulting, the animal stops feeding and its epidermis releases moulting fluid, a mixture of [enzymes](/source/Enzyme) that digests the [endocuticle](/source/Endocuticle) and thus detaches the old cuticle. This phase begins when the [epidermis](/source/Epidermis_(zoology)) has secreted a new [epicuticle](/source/Epicuticle) to protect it from the enzymes, and the epidermis secretes the new exocuticle while the old cuticle is detaching. When this stage is complete, the animal's body swells by taking in a large quantity of water or air, causing the old cuticle to split along predefined weaknesses where the old exocuticle was thinnest. It commonly takes several minutes for the animal to struggle out of the old cuticle. At this point, the new one is wrinkled and so soft that the animal cannot support itself and finds it very difficult to move, and the new endocuticle has not yet formed. The animal continues to pump itself up to stretch the new cuticle as much as possible, then hardens the new exocuticle and eliminates the excess air or water. By the end of this phase, the new endocuticle has formed. Many arthropods then eat the discarded cuticle to reclaim its materials.[37]

Because arthropods are unprotected and nearly immobilized until the new cuticle has hardened, they are in danger both of being trapped in the old cuticle and of being attacked by [predators](/source/Predation). Moulting may be responsible for 80 to 90% of all arthropod deaths.[37]

### Internal organs

Arthropod bodies are also segmented internally, and the nervous, muscular, circulatory, and excretory systems have repeated components.[16] Arthropods come from a lineage of animals that have a [coelom](/source/Coelom), a membrane-lined cavity between the gut and the body wall that accommodates the internal organs. The strong, segmented limbs of arthropods eliminate the need for one of the coelom's main ancestral functions, as a [hydrostatic skeleton](/source/Hydrostatic_skeleton), which muscles compress in order to change the animal's shape and thus enable it to move. Hence the coelom of the arthropod is reduced to small areas around the reproductive and excretory systems. Its place is largely taken by a [hemocoel](/source/Hemocoel), a cavity that runs most of the length of the body and through which [blood](/source/Blood) flows.[38]

### Respiration and circulation

See also: [Hemolymph](/source/Hemolymph) and [hemocyte](/source/Hemocyte)

Arthropods have open [circulatory systems](/source/Circulatory_system). Most have a few short, open-ended [arteries](/source/Artery). In chelicerates and crustaceans, the blood carries [oxygen](/source/Oxygen) to the tissues, while [hexapods](/source/Hexapoda) use a separate system of [tracheae](/source/Invertebrate_trachea). Many crustaceans and a few chelicerates and [tracheates](/source/Tracheata) use [respiratory pigments](/source/Respiratory_pigment) to assist oxygen transport. The most common respiratory pigment in arthropods is [copper](/source/Copper)-based [hemocyanin](/source/Hemocyanin); this is used by many crustaceans and a few [centipedes](/source/Centipede). A few crustaceans and insects use iron-based [hemoglobin](/source/Hemoglobin), the respiratory pigment used by [vertebrates](/source/Vertebrate). As with other invertebrates, the respiratory pigments of those arthropods that have them are generally dissolved in the blood and rarely enclosed in [corpuscles](/source/Blood_cell) as they are in vertebrates.[38]

The heart is a muscular tube that runs just under the back and for most of the length of the hemocoel. It contracts in ripples that run from rear to front, pushing blood forwards. Sections not being squeezed by the heart muscle are expanded either by elastic [ligaments](/source/Ligament) or by small [muscles](/source/Muscle), in either case connecting the heart to the body wall. Along the heart run a series of paired ostia, non-return valves that allow blood to enter the heart but prevent it from leaving before it reaches the front.[38]

Arthropods have a wide variety of respiratory systems. Small species often do not have any, since their high ratio of surface area to volume enables simple diffusion through the body surface to supply enough oxygen. Crustacea usually have gills that are modified appendages. Many arachnids have [book lungs](/source/Book_lung).[39] Tracheae, systems of branching tunnels that run from the openings in the body walls, deliver oxygen directly to individual cells in many insects, myriapods and [arachnids](/source/Arachnid).[40]

### Nervous system

Living arthropods have paired main nerve cords running along their bodies below the gut, and in each segment the cords form a pair of [ganglia](/source/Ganglia) from which [sensory](/source/Sensory_nerve) and [motor](/source/Motor_nerve) nerves run to other parts of the segment. Although the pairs of ganglia in each segment often appear physically fused, they are connected by [commissures](/source/Commissure) (relatively large bundles of nerves), which give arthropod nervous systems a characteristic ladder-like appearance. The brain is in the head, encircling and mainly above the esophagus. It consists of the fused ganglia of the acron and one or two of the foremost segments that form the head – a total of three pairs of ganglia in most arthropods, but only two in chelicerates, which do not have antennae or the ganglion connected to them. The ganglia of other head segments are often close to the brain and function as part of it. In insects, these other head ganglia combine into a pair of [subesophageal ganglia](/source/Subesophageal_ganglia), under and behind the esophagus. Spiders take this process a step further, as all the [segmental ganglia](/source/Segmental_ganglia) are incorporated into the subesophageal ganglia, which occupy most of the space in the cephalothorax (front "super-segment").[41]

### Excretory system

There are two different types of arthropod excretory systems. In aquatic arthropods, the end-product of biochemical reactions that [metabolise](/source/Metabolism) [nitrogen](/source/Nitrogen) is [ammonia](/source/Ammonia), which is so toxic that it needs to be diluted as much as possible with water. The ammonia is then eliminated via any permeable membrane, mainly through the gills.[39] All crustaceans use this system, and its high consumption of water may be responsible for the relative lack of success of crustaceans as land animals.[42] Various groups of terrestrial arthropods have independently developed a different system: the end-product of nitrogen metabolism is [uric acid](/source/Uric_acid), which can be excreted as dry material; the [Malpighian tubule system](/source/Malpighian_tubule_system) filters the uric acid and other nitrogenous waste out of the blood in the hemocoel, and dumps these materials into the hindgut, from which they are expelled as [feces](/source/Feces).[42] Most aquatic arthropods and some terrestrial ones also have organs called [nephridia](/source/Nephridia) ("little [kidneys](/source/Kidney)"), which extract other wastes for excretion as [urine](/source/Urine).[42]

### Senses

The stiff [cuticles](/source/Cuticle) of arthropods would block out information about the outside world, except that they are penetrated by many sensors or connections from sensors to the nervous system. In fact, arthropods have modified their cuticles into elaborate arrays of sensors. Various touch sensors, mostly [setae](/source/Seta), respond to different levels of force, from strong contact to very weak air currents. Chemical sensors provide equivalents of [taste](/source/Taste) and [smell](/source/Olfaction), often by means of setae. Pressure sensors often take the form of membranes that function as [eardrums](/source/Eardrum), but are connected directly to nerves rather than to [auditory ossicles](/source/Auditory_ossicle). The [antennae](/source/Antenna_(biology)) of most hexapods include sensor packages that monitor [humidity](/source/Humidity), moisture and temperature.[43]

Most arthropods lack balance and [acceleration](/source/Acceleration) sensors, and rely on their eyes to tell them which way is up. The self-righting behavior of [cockroaches](/source/Cockroach) is triggered when pressure sensors on the underside of the feet report no pressure. However, many [malacostracan](/source/Malacostracan) crustaceans have [statocysts](/source/Statocyst), which provide the same sort of information as the balance and motion sensors of the vertebrate [inner ear](/source/Inner_ear).[43]

The [proprioceptors](/source/Proprioceptor) of arthropods, sensors that report the force exerted by muscles and the degree of bending in the body and joints, are well understood. However, little is known about what other internal sensors arthropods may have.[43]

#### Optical

Main article: [Arthropod eye](/source/Arthropod_eye)

Arthropods may have sophisticated visual systems that include one or more usually both of [compound eyes](/source/Compound_eye) and pigment-cup [ocelli](/source/Ocelli), ("little eyes"). In most cases, ocelli are only capable of detecting the direction from which light is coming, using the shadow cast by the walls of the cup, although the main eyes of [spiders](/source/Spider) are pigment-cup ocelli that are capable of forming images,[43] and those of [jumping spiders](/source/Jumping_spider) can rotate to track prey.[44]

Compound eyes consist of fifteen to several thousand independent [ommatidia](/source/Ommatidia), columns that are usually [hexagonal](/source/Hexagon) in [cross section](/source/Cross_section_(geometry)). Each ommatidium is an independent sensor, with its own light-sensitive cells and often with its own [lens](/source/Lens_(anatomy)) and [cornea](/source/Cornea).[43] Compound eyes have a wide field of view, and can detect fast movement and, in some cases, the [polarization of light](/source/Light_polarization).[45] On the other hand, the relatively large size of ommatidia makes the images rather coarse, and compound eyes are shorter-sighted than those of birds and mammals – although this is not a severe disadvantage, as objects and events within 20 cm (8 in) are most important to most arthropods.[43] Several arthropods have color vision, and that of some insects has been studied in detail; for example, the ommatidia of bees contain receptors for both green and [ultra-violet](/source/Ultra-violet).[43]

#### Olfaction

Further information: [Insect olfaction](/source/Insect_olfaction)

## Reproduction and development

A few arthropods, such as [barnacles](/source/Barnacle), are [hermaphroditic](/source/Hermaphroditic), that is, each can have the organs of both [sexes](/source/Sex). However, individuals of most species remain of one sex their entire lives.[46] A few species of [insects](/source/Insect) and crustaceans can reproduce by [parthenogenesis](/source/Parthenogenesis), especially if conditions favor a "population explosion". However, most arthropods rely on [sexual reproduction](/source/Sexual_reproduction), and parthenogenetic species often revert to sexual reproduction when conditions become less favorable.[47] The ability to undergo [meiosis](/source/Meiosis) is widespread among arthropods including both those that reproduce sexually and those that reproduce [parthenogenetically](/source/Parthenogenesis).[48] Although meiosis is a major characteristic of arthropods, understanding of its fundamental adaptive benefit has long been regarded as an unresolved problem,[49] that appears to have remained unsettled.

[Aquatic](/source/Aquatic_animal) arthropods may breed by external fertilization, as for example [horseshoe crabs](/source/Horseshoe_crab) do,[50] or by [internal fertilization](/source/Internal_fertilization), where the [ova](/source/Ovum) remain in the female's body and the [sperm](/source/Sperm) must somehow be inserted. All known terrestrial arthropods use internal fertilization. [Opiliones](/source/Opiliones) (harvestmen), [millipedes](/source/Millipede), and some crustaceans use modified appendages such as [gonopods](/source/Gonopod) or [penises](/source/Opiliones_penis) to transfer the sperm directly to the female. However, most male [terrestrial](/source/Terrestrial_animal) arthropods produce [spermatophores](/source/Spermatophore), waterproof packets of [sperm](/source/Sperm), which the females take into their bodies. A few such species rely on females to find spermatophores that have already been deposited on the ground, but in most cases males only deposit spermatophores when complex [courtship rituals](/source/Courtship_ritual) look likely to be successful.[46]

Most arthropods lay eggs,[46] but scorpions are [ovoviviparous](/source/Ovoviviparity): they produce live young after the eggs have hatched inside the mother, and are noted for prolonged maternal care.[51] Newly born arthropods have diverse forms, and insects alone cover the range of extremes. Some hatch as apparently miniature adults (direct development), and in some cases, such as [silverfish](/source/Silverfish), the hatchlings do not feed and may be helpless until after their first moult. Many insects ([Holometabola](/source/Holometabola)) hatch as grubs or [caterpillars](/source/Caterpillar), which do not have segmented limbs or hardened cuticles, and [metamorphose](/source/Metamorphosis) into adult forms by entering an inactive phase in which the larval tissues are broken down and re-used to build the adult body.[52] [Dragonfly](/source/Dragonfly) larvae have the typical cuticles and jointed limbs of arthropods but are flightless water-breathers with extendable jaws.[53] Crustaceans commonly hatch as tiny [nauplius](/source/Nauplius_(larva)) larvae that have only three segments and pairs of appendages.[46]

## Evolutionary history

See also: [Phylogeny of insects](/source/Phylogeny_of_insects)

### Last common ancestor

Based on the distribution of shared [plesiomorphic](/source/Plesiomorphy_and_symplesiomorphy) features in extant and fossil taxa, the [last common ancestor](/source/Last_common_ancestor) of all arthropods is inferred to have been as a modular organism with each module covered by its own [sclerite](/source/Sclerite) (armor plate) and bearing a pair of biramous [limbs](/source/Arthropod_leg).[54] However, whether the ancestral limb was [uniramous or biramous](/source/Arthropod_leg#Biramous_and_uniramous) is far from a settled debate. This Ur-arthropod had a [ventral](/source/Ventral#Dorsal_and_ventral) mouth, pre-oral antennae and [dorsal](/source/Ventral#Dorsal_and_ventral) eyes at the front of the body. It was assumed to have been a non-discriminatory [sediment](/source/Sediment) feeder, processing whatever sediment came its way for food,[54] but fossil findings hint that the last common ancestor of both arthropods and [Priapulida](/source/Priapulida) shared the same specialized mouth apparatus: a circular mouth with rings of teeth used for capturing animal prey.[55]

### Fossil record

It has been proposed that the [Ediacaran](/source/Ediacaran) animals *[Parvancorina](/source/Parvancorina)* and *[Spriggina](/source/Spriggina)*, from around , were arthropods,[56][57][58] but later study shows that their affinities of being origin of arthropods are not reliable.[59] Small arthropods with bivalve-like shells have been found in Early Cambrian fossil beds dating in China and Australia.[60][61][62][63] The earliest Cambrian [trilobite](/source/Trilobite) fossils are about 520 million years old, but the class was already quite diverse and worldwide, suggesting that they had been around for quite some time.[64] In the [Maotianshan shales](/source/Maotianshan_Shales), which date back to 518 million years ago, arthropods such as *[Kylinxia](/source/Kylinxia)* and *[Erratus](/source/Erratus)* have been found that seem to represent [transitional fossils](/source/Transitional_fossil) between stem (e.g. [Radiodonta](/source/Radiodonta) such as *[Anomalocaris](/source/Anomalocaris)*) and true arthropods.[65][66][22] Re-examination in the 1970s of the [Burgess Shale](/source/Burgess_Shale) fossils from about identified many arthropods, some of which could not be assigned to any of the well-known groups, and thus intensified the debate about the [Cambrian explosion](/source/Cambrian_explosion).[67][68][69] A fossil of *[Marrella](/source/Marrella)* from the Burgess Shale has provided the earliest clear evidence of [moulting](/source/Moulting).[70]

The earliest fossil of likely [pancrustacean](/source/Pancrustacean) larvae date from about in the [Cambrian](/source/Cambrian), followed by unique taxa like *[Yicaris](/source/Yicaris)* and *[Wujicaris](/source/Wujicaris)*.[71] The purported pancrustacean/[crustacean](/source/Crustacean) affinity of some cambrian arthropods (e.g. [Phosphatocopina](/source/Phosphatocopina), [Bradoriida](/source/Bradoriida) and [Hymenocarine](/source/Hymenocarina) taxa like waptiids)[72][73][74] were disputed by subsequent studies, as they might branch before the [mandibulate](/source/Mandibulate) crown-group.[71] Within the pancrustacean crown-group, only [Malacostraca](/source/Malacostraca), [Branchiopoda](/source/Branchiopoda) and [Pentastomida](/source/Pentastomida) have Cambrian fossil records.[71] Crustacean fossils are common from the [Ordovician](/source/Ordovician) period onwards.[75] They have remained almost entirely aquatic, possibly because they never developed [excretory systems](/source/Excretory_system) that conserve water.[42]

Arthropods provide the earliest identifiable fossils of land animals, from about in the Late [Silurian](/source/Silurian),[39] and terrestrial tracks from about appear to have been made by arthropods.[76] Arthropods possessed attributes that were easily [coopted](/source/Exaptation) for life on land; their existing jointed exoskeletons provided protection against desiccation, support against gravity and a means of locomotion that was not dependent on water.[77] Around the same time the aquatic, scorpion-like [eurypterids](/source/Eurypterid) became the largest ever arthropods, some as long as 2.5 m (8 ft 2 in).[78]

The oldest known [arachnid](/source/Arachnid) is the [trigonotarbid](/source/Trigonotarbid) *[Palaeotarbus](/source/Palaeotarbus) jerami*, from about in the Silurian period.[79][Note 3] *[Attercopus](/source/Attercopus) fimbriunguis*, from in the [Devonian](/source/Devonian) period, bears the earliest known silk-producing spigots, but its lack of [spinnerets](/source/Spinneret_(spider)) means it was not one of the true [spiders](/source/Spider),[80] which first appear in the Late [Carboniferous](/source/Carboniferous) over .[81] The [Jurassic](/source/Jurassic) and [Cretaceous](/source/Cretaceous) periods provide a large number of fossil spiders, including representatives of many modern families.[82] The oldest known [scorpion](/source/Scorpion) is *[Dolichophonus](/source/Dolichophonus),* dated back to .[83] Lots of Silurian and Devonian scorpions were previously thought to be [gill](/source/Gill)-breathing, hence the idea that scorpions were primitively aquatic and evolved air-breathing [book lungs](/source/Book_lung) later on.[84] However subsequent studies reveal most of them lacking reliable evidence for an aquatic lifestyle,[85] while exceptional aquatic taxa (e.g. *[Waeringoscorpio](/source/Waeringoscorpio)*) most likely derived from terrestrial scorpion ancestors.[86]

The oldest fossil record of [hexapod](/source/Hexapoda) is obscure, as most of the candidates are poorly preserved and their hexapod affinities had been disputed. An iconic example is the Devonian *[Rhyniognatha hirsti](/source/Rhyniognatha_hirsti)*, dated at , its [mandibles](/source/Mandible_(insect_mouthpart)) are thought to be a type found only in [winged insects](/source/Pterygota), which suggests that the earliest insects appeared in the Silurian period.[87] However, later study shows that *Rhyniognatha* most likely represent a myriapod, not even a hexapod.[88] The unequivocal oldest known hexapod is the [springtail](/source/Springtail) *[Rhyniella](/source/Rhyniella)*, from about in the Devonian period, and the [palaeodictyopteran](/source/Palaeodictyoptera) *[Delitzschala bitterfeldensis](/source/Delitzschala_bitterfeldensis)*, from about in the Carboniferous period, respectively.[88] The [Mazon Creek lagerstätten](/source/Mazon_Creek_fossils) from the Late Carboniferous, about , include about 200 species, some gigantic by modern standards, and indicate that insects had occupied their main modern [ecological niches](/source/Ecological_niche) as [herbivores](/source/Herbivore), [detritivores](/source/Detritivore) and [insectivores](/source/Insectivore). Social [termites](/source/Termite) and [ants](/source/Ant) first appear in the Early [Cretaceous](/source/Cretaceous), and advanced social bees have been found in Late Cretaceous rocks but did not become abundant until the Middle [Cenozoic](/source/Cenozoic).[89]

### External phylogeny

From 1952 to 1977, zoologist [Sidnie Manton](/source/Sidnie_Manton) and others argued that arthropods are [polyphyletic](/source/Polyphyly), in other words, that they do not share a common ancestor that was itself an arthropod. Instead, they proposed that three separate groups of "arthropods" evolved separately from common worm-like ancestors: the [chelicerates](/source/Chelicerate), including [spiders](/source/Spider) and [scorpions](/source/Scorpion); the crustaceans; and the [uniramia](/source/Uniramia), consisting of [onychophorans](/source/Onychophoran), [myriapods](/source/Myriapod) and [hexapods](/source/Hexapoda). These arguments usually bypassed [trilobites](/source/Trilobite), as the evolutionary relationships of this class were unclear. Proponents of polyphyly argued the following: that the similarities between these groups are the results of [convergent evolution](/source/Convergent_evolution), as natural consequences of having rigid, segmented [exoskeletons](/source/Exoskeleton); that the three groups use different chemical means of hardening the cuticle; that there were significant differences in the construction of their compound eyes; that it is hard to see how such different configurations of segments and appendages in the head could have evolved from the same ancestor; and that crustaceans have [biramous](/source/Biramous) limbs with separate gill and leg branches, while the other two groups have [uniramous](/source/Uniramous) limbs in which the single branch serves as a leg.[90]

Simplified summary of Budd's (1996) "broad-scale" cladogram[91]

Further analysis and discoveries in the 1990s reversed this view, and led to acceptance that arthropods are [monophyletic](/source/Monophyletic), in other words they are inferred to share a common ancestor that was itself an arthropod.[92][93] For example, [Graham Budd](/source/Graham_Budd)'s analyses of *[Kerygmachela](/source/Kerygmachela)* in 1993 and of *[Opabinia](/source/Opabinia)* in 1996 convinced him that these animals were similar to onychophorans and to various Early Cambrian "[lobopods](/source/Lobopod)", and he presented an "evolutionary family tree" that showed these as "aunts" and "cousins" of all arthropods.[91][94] These changes made the scope of the term "arthropod" unclear, and Claus Nielsen proposed that the wider group should be labelled "[Panarthropoda](/source/Panarthropoda)" ("all the arthropods") while the animals with jointed limbs and hardened cuticles should be called "Euarthropoda" ("true arthropods").[95]

A contrary view was presented in 2003, when Jan Bergström and [Hou Xian-guang](/source/Hou_Xian-guang) argued that, if arthropods were a "sister-group" to any of the anomalocarids, they must have lost and then re-evolved features that were well-developed in the anomalocarids. The earliest known arthropods ate mud in order to extract food particles from it, and possessed variable numbers of segments with unspecialized appendages that functioned as both gills and legs. Anomalocarids were, by the standards of the time, huge and sophisticated predators with specialized mouths and grasping appendages, fixed numbers of segments some of which were specialized, tail fins, and gills that were very different from those of arthropods. In 2006, they suggested that arthropods were more closely related to [lobopods](/source/Lobopod) and [tardigrades](/source/Tardigrade) than to anomalocarids.[96] In 2014, it was found that tardigrades were more closely related to arthropods than velvet worms.[97]

Higher up the "family tree", the [Annelida](/source/Annelida) have traditionally been considered the closest relatives of the Panarthropoda, since both groups have segmented bodies, and the combination of these groups was labelled [Articulata](/source/Articulata_Hypothesis). There had been competing proposals that arthropods were closely related to other groups such as [nematodes](/source/Nematode), [priapulids](/source/Priapulid) and [tardigrades](/source/Tardigrade), but these remained minority views because it was difficult to specify in detail the relationships between these groups.

In the 1990s, [molecular phylogenetic](/source/Molecular_phylogenetics) analyses of [DNA](/source/DNA) sequences produced a coherent scheme showing arthropods as members of a [superphylum](/source/Superphylum) labelled Ecdysozoa ("animals that moult"), which contained nematodes, priapulids and tardigrades but excluded annelids. This was backed up by studies of the anatomy and development of these animals, which showed that many of the features that supported the Articulata hypothesis showed significant differences between annelids and the earliest Panarthropods in their details, and some were hardly present at all in arthropods. This hypothesis groups annelids with molluscs and [brachiopods](/source/Brachiopod) in another superphylum, [Lophotrochozoa](/source/Lophotrochozoa).

If the Ecdysozoa hypothesis is correct, then segmentation of arthropods and annelids either has evolved [convergently](/source/Convergent_evolution) or has been inherited from a much older ancestor and subsequently lost in several other lineages, such as the non-arthropod members of the Ecdysozoa.[98][99]

### Internal phylogeny

#### Early arthropods

Further information: [Deuteropoda](/source/Deuteropoda)

Aside from the four major living groups ([crustaceans](/source/Crustacea), [chelicerates](/source/Chelicerate), [myriapods](/source/Myriapod) and [hexapods](/source/Hexapoda)), a number of fossil forms, mostly from the early Cambrian period, are difficult to place taxonomically, either from lack of obvious affinity to any of the main groups or from clear affinity to several of them. *[Marrella](/source/Marrella)* was the first one to be recognized as significantly different from the well-known groups.[28]

Modern interpretations of the basal, extinct [stem-group](/source/Stem-group) of Arthropoda recognised the following groups, from most basal to most crownward:[100][101]

- The ["Giant" or "Siberiid Lobopodians"](/source/Lobopodia#Siberion_and_similar_taxa), such as *[Jianshanopodia](/source/Jianshanopodia)*, *[Siberion](/source/Siberion)* and *[Megadictyon](/source/Megadictyon)*, are the most basal [grade](/source/Evolutionary_grade) in the total-group Arthropoda.
- The ["Gilled Lobopodians"](/source/Lobopodia#Gilled_lobopodians), such as *[Kerygmachela](/source/Kerygmachela)*, *[Pambdelurion](/source/Pambdelurion)* and *[Opabinia](/source/Opabinia)*, are the second most basal grade.
- The [Radiodonta](/source/Radiodonta), which traditionally known as anomalocaridids come in third position, and are thought to be [monophyletic](/source/Monophyly).
- A possible "upper stem-group" assemblage of more uncertain position[101] but contained within [Deuteropoda](/source/Deuteropoda):[100] the [Fuxianhuiida](/source/Fuxianhuiida), [Megacheira](/source/Megacheira), and multiple "bivalved forms" including [Isoxyida](/source/Isoxyida) and [Hymenocarina](/source/Hymenocarina).

The [Deuteropoda](/source/Deuteropoda) is a recently established clade uniting the crown-group (living) arthropods with these possible "upper stem-group" fossils taxa.[100] The clade is defined by important changes to the structure of the head region such as the appearance of a differentiated [deutocerebral](/source/Deutocerebrum) appendage pair, which excludes more basal taxa like radiodonts and "gilled lobopodians".[100]

Controversies remain about the positions of various extinct arthropod groups. Some studies recover Megacheira as closely related to chelicerates, while others recover them as outside the group containing Chelicerate and Mandibulata as stem-group euarthropods.[102] The placement of the [Artiopoda](/source/Artiopoda) (which contains the extinct trilobites and similar forms) is also a frequent subject of dispute.[103] The main hypotheses position them in the clade [Arachnomorpha](/source/Arachnomorpha) with the Chelicerates. However, one of the newer hypotheses is that the chelicerae have originated from the same pair of appendages that evolved into antennae in the ancestors of [Mandibulata](/source/Mandibulata), which would place trilobites, which had antennae, closer to Mandibulata than Chelicerata, in the clade [Antennulata](/source/Antennulata).[102][104] The [fuxianhuiids](/source/Fuxianhuiida), usually suggested to be stem-group arthropods, have been suggested to be Mandibulates in some recent studies.[102] The [Hymenocarina](/source/Hymenocarina), a group of bivalved arthropods, previously thought to have been stem-group members of the group, have been demonstrated to be mandibulates based on the presence of mandibles.[101]

Cladogram after Liu et al, 2026:[105]List of arthropod groups and genera († denotes extinct taxa)

- "[Dinocaridida](/source/Dinocaridida)" [†](/source/Extinction) (generally considered [paraphyletic](/source/Paraphyletic),[106] sometimes treated as [lobopodians](/source/Lobopodia)) - [Kerygmachelidae](/source/Kerygmachelidae) †[106] - *[Pambdelurion](/source/Pambdelurion)* † (possible lobopodian)[102] - *[Mieridduryn](/source/Mieridduryn)* † (possible [opabiniid](/source/Opabiniid))[107] - *[Parvibellus](/source/Parvibellus)* † (possible ["Siberiid Lobopodian"](/source/Lobopodia#Siberion_and_similar_taxa))[108] - [Opabiniidae](/source/Opabiniidae) †[106] - [Radiodonta](/source/Radiodonta) †[106] - *[Cucumericrus](/source/Cucumericrus)* † (possible radiodont) - *[Caryosyntrips](/source/Caryosyntrips)* † (possible radiodont)
- [Deuteropoda](/source/Deuteropoda)[106] - [Artiopoda](/source/Artiopoda) †[102] - [Trilobita](/source/Trilobita) †[109] - [Agnostida](/source/Agnostida) (possibly trilobites)[110] † - [Nektaspida](/source/Nektaspida) †[109] - [Aglaspidida](/source/Aglaspidida) †[109] - [Cheloniellida](/source/Cheloniellida) †[109] - *[Bushizheia](/source/Bushizheia)* †[111] - *[Erratus](/source/Erratus)*[112] † - *[Fengzhengia](/source/Fengzhengia)*[113] † - [Isoxyida](/source/Isoxyida) †[114] - *[Kiisortoqia](/source/Kiisortoqia)* †[111] - *[Kylinxia](/source/Kylinxia)*[66] † - [Marrellomorpha](/source/Marrellomorpha) †[115] - [Bradoriida](/source/Bradoriida) †[116] - [Megacheira](/source/Megacheira) † (possibly paraphyletic, alternatively placed as stem-chelicerates)[117] - [Chelicerata](/source/Chelicerata)[102] - [Habeliida](/source/Habeliida) †[102] - [Pycnogonida](/source/Pycnogonida) - [Prosomapoda](/source/Prosomapoda) - "[Synziphosurina](/source/Synziphosurina)" (paraphyletic) - [Xiphosura](/source/Xiphosura) - [Dekatriata](/source/Dekatriata)[118] - [Chasmataspidida](/source/Chasmataspidida) † - [Eurypterida](/source/Eurypterida) † - [Arachnida](/source/Arachnida) - [Phosphatocopina](/source/Phosphatocopina) (possible stem mandibulate)[119] † - [Mandibulata](/source/Mandibulata)[102] - [Fuxianhuiida](/source/Fuxianhuiida) †[120] - [Hymenocarina](/source/Hymenocarina) †[121] - [Euthycarcinoidea](/source/Euthycarcinoidea) †[122] - [Thylacocephala](/source/Thylacocephala)?[123] † - [Myriapoda](/source/Myriapoda) - [Pancrustacea](/source/Pancrustacea)[124] - [Oligostraca](/source/Oligostraca) - [Ostracoda](/source/Ostracoda) - [Mystacocarida](/source/Mystacocarida) - [Ichthyostraca](/source/Ichthyostraca) - [Multicrustacea](/source/Multicrustacea) - [Cyclida](/source/Cyclida)[125] † - [Thecostraca](/source/Thecostraca) - [Tantulocarida](/source/Tantulocarida) - [Copepoda](/source/Copepoda) - [Malacostraca](/source/Malacostraca) - [Allotriocarida](/source/Allotriocarida) - [Cephalocarida](/source/Cephalocarida) - [Branchiopoda](/source/Branchiopoda) - [Remipedia](/source/Remipedia) - [Hexapoda](/source/Hexapoda) - [Collembola](/source/Collembola) - [Protura](/source/Protura) - [Diplura](/source/Diplura) - [Insecta](/source/Insecta)
- *[Incertae sedis](/source/Incertae_sedis)* - *[Aaveqaspis](/source/Aaveqaspis)*[126] † - *[Arthrogyrinus](/source/Arthrogyrinus)*[127] † - *[Bennettarthra](/source/Bennettarthra)* [128] † - *[Burgessia](/source/Burgessia)*[129] † - [Cambropachycopidae](/source/Cambropachycopidae)[130] † - *[Cambropodus](/source/Cambropodus)*[131] † - *[Camptophyllia](/source/Camptophyllia)*[132] † - *[Chuandianella](/source/Chuandianella)*[133] † - *[Keurbos](/source/Keurbos)*[134] † - *[Notchia](/source/Notchia)*[135] † - *[Papiliomaris](/source/Papiliomaris)*[136] † - *[Parioscorpio](/source/Parioscorpio)*[137] † - *[Pleuralata](/source/Pleuralata)*[138] † - *[Rhynimonstrum](/source/Rhynimonstrum)* [139] † - *[Sarotrocercus](/source/Sarotrocercus)*[140] † - [Strabopida](/source/Strabopidae)[141] † - [Sunellidae](/source/Sunellidae)[142] † - *[Wingertshellicus](/source/Wingertshellicus)*[143] † - *[Zhenghecaris](/source/Zhenghecaris)*[144] †

#### Living arthropods

See also: [List of arthropod orders](/source/List_of_arthropod_orders)

The phylum Arthropoda is typically [subdivided](/source/Scientific_classification) into four [subphyla](/source/Subphylum), of which one is [extinct](/source/Extinct):[145]

1. **[Artiopods](/source/Artiopoda)** are an extinct group of formerly numerous marine arthropods. They were reduced to a handful of orders in the [Late Devonian extinction](/source/Late_Devonian_extinction), then became extinct in the [Permian–Triassic extinction event](/source/Permian%E2%80%93Triassic_extinction_event).[146] They contain groups such as the [trilobites](/source/Trilobita), [nektaspids](/source/Nektaspida), [aglaspidids](/source/Aglaspidida), and the [cheloniellids](/source/Cheloniellida) among others.
1. **[Chelicerates](/source/Chelicerata)** comprise the marine [sea spiders](/source/Sea_spider) and [horseshoe crabs](/source/Horseshoe_crab), along with the terrestrial [arachnids](/source/Arachnid) such as [mites](/source/Mite), [harvestmen](/source/Harvestmen), [spiders](/source/Spider), [scorpions](/source/Scorpion) and related organisms characterized by the presence of [chelicerae](/source/Chelicerae), [appendages](/source/Appendage) just above/in front of the [mouthparts](/source/Arthropod_mouthparts). Chelicerae appear in scorpions and horseshoe crabs as tiny [claws](/source/Claw) that they use in feeding, but those of spiders have developed as [fangs](/source/Fang) that inject [venom](/source/Venom).
1. **[Myriapods](/source/Myriapoda)** comprise [millipedes](/source/Millipede), [centipedes](/source/Centipede), [pauropods](/source/Pauropod) and [symphylans](/source/Symphylan), characterized by having numerous [body segments](/source/Body_segment) each of which bearing one or two pairs of legs (or in a few cases being legless). All members are exclusively terrestrial.
1. **[Pancrustaceans](/source/Pancrustacea)** comprise [ostracods](/source/Ostracod), [barnacles](/source/Barnacle), [copepods](/source/Copepod), [malacostracans](/source/Malacostracan), [cephalocaridans](/source/Cephalocaridan), [branchiopods](/source/Branchiopod), [remipedes](/source/Remipedes) and [hexapods](/source/Hexapoda). Most groups are primarily [aquatic](/source/Aquatic_animal) (two notable exceptions being [woodlice](/source/Woodlouse) and hexapods, which are both purely [terrestrial](/source/Terrestrial_animal)) and are characterized by having [biramous](/source/Arthropod_leg#Biramous_and_uniramous) appendages. The most abundant group of pancrustaceans are the terrestrial hexapods, which comprise [insects](/source/Insect), [diplurans](/source/Diplura), [springtails](/source/Springtails), and [proturans](/source/Protura), with six [thoracic](/source/Thorax_(arthropod_anatomy)) legs.

The [phylogeny](/source/Phylogenetics) of the major extant arthropod groups has been an area of considerable interest and dispute.[147] Recent studies strongly suggest that Crustacea, as traditionally defined, is [paraphyletic](/source/Paraphyly), with Hexapoda having evolved from within it,[148][149] so that Crustacea and Hexapoda form a clade, [Pancrustacea](/source/Pancrustacea). The position of [Myriapoda](/source/Myriapoda), [Chelicerata](/source/Chelicerata) and Pancrustacea remains unclear as of April 2012. In some studies, Myriapoda is grouped with Chelicerata (forming [Myriochelata](/source/Myriochelata));[150][151] in other studies, Myriapoda is grouped with Pancrustacea (forming [Mandibulata](/source/Mandibulata)),[148] or Myriapoda may be sister to Chelicerata plus Pancrustacea.[149]

The following cladogram shows the internal relationships between all the living [classes](/source/Class_(biology)) of arthropods as of the late 2010s,[152][153][154] as well as the estimated timing for some of the clades:[155]

Subphyla Classes Members Example species Chelicerata Pycnogonida Xiphosura Arachnida sea spiders horseshoe crabs harvestmen, solifuges, mites, scorpions, spiders, ticks etc. Platycryptus undatus (Arachnida, Araneae) Myriapoda Symphyla Pauropoda Diplopoda Chilopoda pseudocentipedes hexameroceratans, tetrameroceratans bristle millipedes, pill millipedes, flat-backed millipedes, etc. scutigeromorphs, lithobiomorphs, Scolopendromorphs, etc. Archispirostreptus gigas (Diplopoda, Spirostreptida) Crustacea Ostracoda Mystacocarida Pentastomida Branchiura Thecostraca Copepoda Malacostraca Cephalocarida Branchiopoda Remipedia seed shrimp Mystacocaridans tongue worms fish lice barnacles, etc. calanoids, cyclopoids, misophrioids, siphonostomatoids, etc. mantis shrimp, skeleton shrimp, woodlice, shrimp, crabs, lobsters, krill, etc. horseshoe shrimp fairy shrimp, tadpole shrimp, water fleas, clam shrimp remipedes Ocypode ceratophthalma (Malacostraca, Decapoda) Hexapoda Insecta Entognatha insects springtails, etc. Saturnia pavonia (Insecta, Lepidoptera)

## Interaction with humans

Main article: [Arthropods in culture](/source/Arthropods_in_culture)

See also: [Insects as food](/source/Insects_as_food)

[Crustaceans](/source/Crustacean) such as [crabs](/source/Crab), [lobsters](/source/Lobster), [crayfish](/source/Crayfish), [shrimp](/source/Shrimp), and [prawns](/source/Prawn) have long been part of human cuisine, and are now raised commercially.[156] Insects and their grubs are at least as nutritious as meat, and are eaten both raw and cooked in many cultures, though not most European, Hindu, and Islamic cultures.[157][158] Cooked [tarantulas](/source/Tarantula) are considered a delicacy in [Cambodia](/source/Cambodia),[159][160][161] and by the [Piaroa Indians](/source/Piaroa_people) of southern [Venezuela](/source/Venezuela), after the highly irritant hairs – the spider's main defense system – are removed.[162] Humans also [unintentionally eat](/source/Entomophagy#Unintentional_ingestion) arthropods in other foods,[163] and food safety regulations lay down acceptable contamination levels for different kinds of food material.[Note 4][Note 5] The intentional cultivation of arthropods and other small animals for human food, referred to as [minilivestock](/source/Minilivestock), is now emerging in [animal husbandry](/source/Animal_husbandry) as an ecologically sound concept.[164] [Commercial butterfly breeding](/source/Commercial_butterfly_breeding) provides Lepidoptera stock to [butterfly conservatories](/source/Butterfly_house), educational exhibits, schools, research facilities, and cultural events.

However, the greatest contribution of arthropods to human food supply is by [pollination](/source/Pollination): A 2008 study examined the 100 crops that FAO lists as grown for food, and estimated pollination's economic value as €153 billion, or 9.5 per cent of the value of world agricultural production used for human food in 2005.[165] Besides pollinating, [bees](/source/Bee) produce [honey](/source/Honey), which is the basis of a rapidly growing industry and international trade.[166]

The red dye [cochineal](/source/Cochineal), produced from a Central American species of insect, was economically important to the [Aztecs](/source/Aztecs) and [Mayans](/source/Maya_civilization).[167] While the region was under [Spanish](/source/Spain) control, it became [Mexico](/source/Mexico)'s second most-lucrative export,[168] and is now regaining some of the ground it lost to synthetic competitors.[169] [Shellac](/source/Shellac), a resin secreted by a species of insect native to southern Asia, was historically used in great quantities for many applications in which it has mostly been replaced by synthetic resins, but it is still used in [woodworking](/source/Woodworking) and as a [food additive](/source/Food_additive). The blood of horseshoe crabs contains a clotting agent, [limulus amebocyte lysate](/source/Limulus_amebocyte_lysate), which is now used to test that [antibiotics](/source/Antibiotic) and kidney machines are free of dangerous [bacteria](/source/Bacteria), and to detect [spinal meningitis](/source/Spinal_meningitis). [Forensic entomology](/source/Forensic_entomology) uses evidence provided by arthropods to establish the time and sometimes the place of death of a human, and in some cases the cause.[170] Recently insects have also gained attention as potential sources of drugs and other medicinal substances.[171]

The relative simplicity of the arthropods' body plan, allowing them to move on a variety of surfaces both on land and in water, have made them useful as models for [robotics](/source/Robotics). The redundancy provided by segments allows arthropods and [biomimetic](/source/Biomimetics) robots to move normally, even with damaged or lost appendages.[172][173]

Diseases transmitted by insects Disease[174] Insect Cases per year Deaths per year Malaria Anopheles mosquito 267 M 1 to 2 M Dengue fever Aedes mosquito 5 M 5,000 Yellow fever Aedes mosquito 4,432 1,177 Filariasis Culex mosquito 250 M unknown

Although arthropods are the most numerous phylum on Earth, and thousands of arthropod species are venomous, they inflict relatively few serious bites and stings on humans. Far more serious are the effects on humans of diseases like [malaria](/source/Malaria) carried by [blood-sucking](/source/Hematophagy) insects. Other blood-sucking insects infect livestock with diseases that kill many animals and greatly reduce the usefulness of others.[174] [Ticks](/source/Tick) can cause [tick paralysis](/source/Tick_paralysis) and several [parasite](/source/Parasite)-borne diseases in humans.[175] A few of the closely related [mites](/source/Mite) also infest humans, causing intense itching,[176] and others cause [allergic](/source/Allergy) diseases, including [hay fever](/source/Hay_fever), [asthma](/source/Asthma), and [eczema](/source/Eczema).[177]

Many species of arthropods, principally insects but also mites, are agricultural and forest pests.[178][179] The mite *[Varroa destructor](/source/Varroa_destructor)* has become the largest single problem faced by [beekeepers](/source/Beekeeper) worldwide.[180] Efforts to control arthropod pests by large-scale use of [pesticides](/source/Pesticide) have caused long-term effects on human health and on [biodiversity](/source/Biodiversity).[181] Increasing arthropod [resistance](/source/Pesticide_resistance) to pesticides has led to the development of [integrated pest management](/source/Integrated_pest_management) using a wide range of measures including [biological control](/source/Biological_control).[178] [Predatory](/source/Predator) mites may be useful in controlling some mite pests.[182][183]

## See also

- [Dorsal lobe](/source/Dorsal_lobe)
- [Invertebrate paleontology](/source/Invertebrate_paleontology)
- [Minibeasts](/source/Minibeasts)

## Notes

1. The [Museum of New Zealand](/source/Museum_of_New_Zealand) notes that "in everyday conversation", *bug* "refers to land arthropods with at least six legs, such as insects, spiders, and centipedes".[184] In a chapter on "Bugs That Are Not Insects", entomologist Gilbert Walbauer specifies [centipedes](/source/Centipede), [millipedes](/source/Millipede), [arachnids](/source/Arachnid) ([spiders](/source/Spider), [daddy longlegs](/source/Opiliones), [scorpions](/source/Scorpion), [mites](/source/Mite), [chiggers](/source/Chigger) and [ticks](/source/Tick)) as well as the few terrestrial [crustaceans](/source/Crustacean) ([sowbugs](/source/Sowbug) and [pillbugs](/source/Pillbug)),[185] but argues that "including legless creatures such as worms, slugs, and snails among the bugs stretches the word too much".[7]

1. "It would be too bad if the question of head segmentation ever should be finally settled; it has been for so long such fertile ground for theorizing that arthropodists would miss it as a field for mental exercise."[186]

1. The fossil was originally named *Eotarbus* but was renamed when it was realized that a [Carboniferous](/source/Carboniferous) arachnid had already been named *[Eotarbus](/source/Eotarbus)*.[187]

1. For a mention of insect contamination in an international food quality standard, see sections 3.1.2 and 3.1.3 of Codex 152 of 1985 of the [Codex Alimentarius](/source/Codex_Alimentarius).[188]

1. For examples of quantified acceptable insect contamination levels in food see the last entry (on "Wheat Flour") and the definition of "Extraneous material" in *Codex Alimentarius*,[189] and the standards published by the FDA.[190]

## References

1. Martínez-Muñoz, Carlos A. (2023-05-04). "The correct authorship of Arthropoda—A reappraisal". *Integrative Systematics*. **6** (1): 1–8. [doi:10.18476/2023.472723](https://doi.org/10.18476/2023.472723). [ISSN 2628-2380](https://www.worldcat.org/issn/2628-2380). [S2CID 258497632](https://api.semanticscholar.org/CorpusID:258497632)

1. Gravenhorst, J. L. C. (1843). [*Vergleichende Zoologie*](https://www.biodiversitylibrary.org/item/120240#page/24/mode/1up). Breslau: Druck und Verlag von Graß, Barth und Comp.

1. Retrieved 2024-05-12.

1. ["Arthropoda"](http://www.etymonline.com/index.php?term=Arthropoda&allowed_in_frame=0). [Online Etymology Dictionary](/source/Online_Etymology_Dictionary). [Archived](https://web.archive.org/web/20130307075628/http://www.etymonline.com/index.php?term=Arthropoda&allowed_in_frame=0) 2013-03-07 at the Wayback Machine. Retrieved 2013-05-23.

1. Gravenhorst, J. L. C. (1843). [*Vergleichende Zoologie*](https://www.biodiversitylibrary.org/page/38963736) [Comparative Zoology] (in German). Breslau, (Prussia): Graß, Barth & Comp. p. foldout. *"Mit gegliederten Bewegungsorganen"* (with articulated movement organs)

1. Gilbert Waldbauer. *The Handy Bug Answer Book.* Visible Ink, 1998. [p. 1.](https://archive.org/details/handybuganswerbo00wald/page/1/mode/2up) ISBN 978-1-57859-049-0

1. Valentine, J. W. (2004), [*On the Origin of Phyla*](https://books.google.com/books?id=DMBkmHm5fe4C&q=arthropod+synapomorphy), [University of Chicago Press](/source/University_of_Chicago_Press), p. 33, ISBN 978-0-226-84548-7

1. Cutler, B. (August 1980), "Arthropod cuticle features and arthropod monophyly", *[Cellular and Molecular Life Sciences](/source/Cellular_and_Molecular_Life_Sciences)*. **36** (8): 953, [doi:10.1007/BF01953812](https://doi.org/10.1007/BF01953812). [S2CID 84995596](https://api.semanticscholar.org/CorpusID:84995596)

1. [Australian Beetles Volume 2: Archostemata, Myxophaga, Adephaga, Polyphaga](https://books.google.com/books?id=hHW7DwAAQBAJ&dq=Penetini+Archaeoglenini+calcium+carbonate&pg=PT1017)

1. Kovoor, J. (1978). "Natural calcification of the prosomatic endosternite in the Phalangiidae (Arachnida: Opiliones).". *Calcified Tissue Research*. **26** (3): 267–9. [doi:10.1007/BF02013269](https://doi.org/10.1007/BF02013269). [PMID 750069](https://pubmed.ncbi.nlm.nih.gov/750069). [S2CID 23119386](https://api.semanticscholar.org/CorpusID:23119386)

1. Rong, Jingjing; Lin, Yubo; Sui, Zhuoxiao; Wang, Sijia; Wei, Xunfan; Xiao, Jinhua; Huang, Dawei (November–December 2019). ["Amorphous calcium phosphate in the pupal cuticle of *Bactrocera dorsalis* Hendel (Diptera: Tephritidae): A new discovery for reconsidering the mineralization of the insect cuticle"](https://linkinghub.elsevier.com/retrieve/pii/S0022191019301623). *Journal of Insect Physiology*. **119**. [Bibcode:2019JInsP.11903964R](https://ui.adsabs.harvard.edu/abs/2019JInsP.11903964R). [doi:10.1016/j.jinsphys.2019.103964](https://doi.org/10.1016/j.jinsphys.2019.103964). [PMID 31604063](https://pubmed.ncbi.nlm.nih.gov/31604063)

1. Thanukos, Anna, ["The Arthropod Story"](http://evolution.berkeley.edu/evolibrary/article/arthropodstory), [University of California, Berkeley](/source/University_of_California,_Berkeley), [archived](https://web.archive.org/web/20080616122532/http://evolution.berkeley.edu/evolibrary/article/arthropodstory) 2008-06-16 at the Wayback Machine, retrieved 2008-09-29

1. Ødegaard, Frode (December 2000), ["How many species of arthropods? Erwin's estimate revised"](http://si-pddr.si.edu/dspace/bitstream/10088/1315/1/Odegaard_2000.pdf), *[Biological Journal of the Linnean Society](/source/Biological_Journal_of_the_Linnean_Society)*. **71** (4): 583–597, [Bibcode:2000BJLS...71..583O](https://ui.adsabs.harvard.edu/abs/2000BJLS...71..583O). [doi:10.1006/bijl.2000.0468](https://doi.org/10.1006/bijl.2000.0468), [archived](https://web.archive.org/web/20101226022738/http://si-pddr.si.edu/dspace/bitstream/10088/1315/1/Odegaard_2000.pdf) 2010-12-26 at the Wayback Machine, retrieved 2010-05-06

1. Thompson, J. N. (1994), [*The Coevolutionary Process*](https://books.google.com/books?id=AyXPQzEwqPIC&q=arthropod+species+number&pg=PA9), [University of Chicago Press](/source/University_of_Chicago_Press), p. 9, ISBN 978-0-226-79760-1

1. [Ruppert, Fox & Barnes (2004)](#refRuppert), pp. 518–522

1. Mohrbeck, Inga; Martínez Arbizu, Pedro; Glatzel, Thomas (October 2010). "Tantulocarida (Crustacea) of the Southern Ocean deep sea, and the description of three new species of *Tantulacus* (Huys, Andersen & Kristensen, 1992)". *[Systematic Parasitology](/source/Systematic_Parasitology)*. **77** (2): 131–151. [doi:10.1007/s11230-010-9260-0](https://doi.org/10.1007/s11230-010-9260-0). [PMID 20852984](https://pubmed.ncbi.nlm.nih.gov/20852984). [S2CID 7325858](https://api.semanticscholar.org/CorpusID:7325858)

1. Schmidt-Nielsen, Knut (1984), ["The strength of bones and skeletons"](https://archive.org/details/scalingwhyisanim0000schm/page/42), *Scaling: Why is animal size so important?*, [Cambridge University Press](/source/Cambridge_University_Press), pp. [42–55](https://archive.org/details/scalingwhyisanim0000schm/page/42), ISBN 978-0-521-31987-4

1. Gould (1990), pp. 102–106.

1. Ortega-Hernández, Javier; Janssen, Ralf; Budd, Graham E. (2017). "Origin and evolution of the panarthropod head – A palaeobiological and developmental perspective". *Arthropod Structure & Development*. **46** (3): 354–379. [Bibcode:2017ArtSD..46..354O](https://ui.adsabs.harvard.edu/abs/2017ArtSD..46..354O). [doi:10.1016/j.asd.2016.10.011](https://doi.org/10.1016/j.asd.2016.10.011). [PMID 27989966](https://pubmed.ncbi.nlm.nih.gov/27989966)

1. ["Giant sea creature hints at early arthropod evolution"](http://news.yale.edu/2015/03/11/giant-sea-creature-hints-early-arthropod-evolution). 2015-03-11. [Archived](https://web.archive.org/web/20170202020956/http://news.yale.edu/2015/03/11/giant-sea-creature-hints-early-arthropod-evolution) 2017-02-02 at the Wayback Machine. Retrieved 2017-01-22.

1. Fu, D.; Legg, D. A.; Daley, A. C.; Budd, G. E.; Wu, Y.; Zhang, X. (2022). "The evolution of biramous appendages revealed by a carapace-bearing Cambrian arthropod". *Philosophical Transactions of the Royal Society B: Biological Sciences*. **377** (1847). [doi:10.1098/rstb.2021.0034](https://doi.org/10.1098/rstb.2021.0034). [PMC 8819368](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8819368). [PMID 35125000](https://pubmed.ncbi.nlm.nih.gov/35125000). [S2CID 246608509](https://api.semanticscholar.org/CorpusID:246608509)

1. Liu, Yu; Edgecombe, Gregory D.; Schmidt, Michel; Bond, Andrew D.; Melzer, Roland R.; Zhai, Dayou; Mai, Huijuan; Zhang, Maoyin; Hou, Xianguang (2021-07-30). "Exites in Cambrian arthropods and homology of arthropod limb branches". *Nature Communications*. **12** (1): 4619. [Bibcode:2021NatCo..12.4619L](https://ui.adsabs.harvard.edu/abs/2021NatCo..12.4619L). [doi:10.1038/s41467-021-24918-8](https://doi.org/10.1038/s41467-021-24918-8). [ISSN 2041-1723](https://www.worldcat.org/issn/2041-1723). [PMC 8324779](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8324779). [PMID 34330912](https://pubmed.ncbi.nlm.nih.gov/34330912)

1. Hejnol, Andreas & Scholtz, Gerhard (2004-10-01). "Clonal analysis of Distal-less and engrailed expression patterns during early morphogenesis of uniramous and biramous crustacean limbs". *Development Genes and Evolution*. **214** (10): 473–485. [doi:10.1007/s00427-004-0424-2](https://doi.org/10.1007/s00427-004-0424-2). [ISSN 1432-041X](https://www.worldcat.org/issn/1432-041X). [PMID 15300435](https://pubmed.ncbi.nlm.nih.gov/15300435). [S2CID 22426697](https://api.semanticscholar.org/CorpusID:22426697)

1. Wolff, Carsten & Scholtz, Gerhard (2008-05-07). "The clonal composition of biramous and uniramous arthropod limbs". *Proceedings of the Royal Society B: Biological Sciences*. **275** (1638): 1023–1028. [Bibcode:2008PBioS.275.1023W](https://ui.adsabs.harvard.edu/abs/2008PBioS.275.1023W). [doi:10.1098/rspb.2007.1327](https://doi.org/10.1098/rspb.2007.1327). [PMC 2600901](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2600901). [PMID 18252674](https://pubmed.ncbi.nlm.nih.gov/18252674)

1. Shubin, Neil; Tabin, C.; Carroll, Sean (2000), ["Fossils, Genes and the Evolution of Animal Limbs"](https://books.google.com/books?id=M6yF0pU4eCsC&q=arthropod+diversity&pg=PA110), *Shaking the Tree: Readings from Nature in the History of Life*, Gee, H. (ed.), [University of Chicago Press](/source/University_of_Chicago_Press), p. 110, ISBN 978-0-226-28497-2

1. Dunlop, Jason A. & Lamsdell, James C. (2017). ["Segmentation and tagmosis in Chelicerata"](https://linkinghub.elsevier.com/retrieve/pii/S1467803916300731). *Arthropod Structure & Development*. **46** (3): 395–418. [Bibcode:2017ArtSD..46..395D](https://ui.adsabs.harvard.edu/abs/2017ArtSD..46..395D). [doi:10.1016/j.asd.2016.05.002](https://doi.org/10.1016/j.asd.2016.05.002). [PMID 27240897](https://pubmed.ncbi.nlm.nih.gov/27240897)

1. Whittington, H. B. (1971), "Redescription of *Marrella splendens* (Trilobitoidea) from the Burgess Shale, Middle Cambrian, British Columbia", *[Geological Survey of Canada Bulletin](/source/Geological_Survey_of_Canada_Bulletin)*. **209**: 1–24 Summarised in (Gould 1990, pp. 107–121).

1. Budd, G. E. (16 May 2002). "A palaeontological solution to the arthropod head problem". *[Nature](/source/Nature_(journal))*. **417** (6886): 271–275. [Bibcode:2002Natur.417..271B](https://ui.adsabs.harvard.edu/abs/2002Natur.417..271B). [doi:10.1038/417271a](https://doi.org/10.1038/417271a). [PMID 12015599](https://pubmed.ncbi.nlm.nih.gov/12015599). [S2CID 4310080](https://api.semanticscholar.org/CorpusID:4310080)

1. Wainwright, S. A.; Biggs, W. D.; & Gosline, J. M. (1982). [*Mechanical Design in Organisms*](https://archive.org/details/mechanicaldesign0000unse/page/162). [Princeton University Press](/source/Princeton_University_Press). pp. [162–163](https://archive.org/details/mechanicaldesign0000unse/page/162). ISBN 978-0-691-08308-7.

1. Lowenstam, H. A. & Weiner, S. (1989), [*On biomineralization*](https://books.google.com/books?id=JbAgy0AAopsC&q=arthropod+biomineralization), Oxford University Press, p. 111, ISBN 978-0-19-504977-0

1. Cohen, B. L. (2005), ["Not armour, but biomechanics, ecological opportunity and increased fecundity as keys to the origin and expansion of the mineralized benthic metazoan fauna"](http://eprints.gla.ac.uk/2933/01/Cohen_2933.pdf), *[Biological Journal of the Linnean Society](/source/Biological_Journal_of_the_Linnean_Society)*. **85** (4): 483–490, [doi:10.1111/j.1095-8312.2005.00507.x](https://doi.org/10.1111/j.1095-8312.2005.00507.x), [archived](https://web.archive.org/web/20081003122813/http://eprints.gla.ac.uk/2933/01/Cohen_2933.pdf) 2008-10-03 at the Wayback Machine, retrieved 2008-09-25

1. Bengtson, S. (2004). ["Early skeletal fossils"](http://www.starregister.org/download/18.4e32c81078a8d9249800021554/Bengtson2004ESF.pdf). *Neoproterozoic-Cambrian Biological Revolutions*. Vol. 10. The Paleontological Society Papers. Lipps, J. H. & Waggoner, B. M. (eds.). pp. 67–78. [doi:10.1017/S1089332600002345](https://doi.org/10.1017/S1089332600002345). [Archived](https://web.archive.org/web/20081003122817/http://www.nrm.se/download/18.4e32c81078a8d9249800021554/Bengtson2004ESF.pdf) 2008-10-03 at the Wayback Machine.

1. Barnes, R. S. K.; Calow, P.; Olive, P.; Golding, D.; & Spicer, J. (2001), ["Invertebrates with Legs: the Arthropods and Similar Groups"](https://books.google.com/books?id=TBMsbe9efPgC&q=arthropod+hydraulic&pg=PA168), *The Invertebrates: A Synthesis*, [Blackwell Publishing](/source/Blackwell_Publishing), p. 168, ISBN 978-0-632-04761-1

1. Parry, D. A. & Brown, R. H. J. (1959), ["The hydraulic mechanism of the spider leg"](http://jeb.biologists.org/cgi/reprint/36/2/423.pdf), *[Journal of Experimental Biology](/source/Journal_of_Experimental_Biology)*. **36** (2): 423–433, [Bibcode:1959JExpB..36..423P](https://ui.adsabs.harvard.edu/abs/1959JExpB..36..423P). [doi:10.1242/jeb.36.2.423](https://doi.org/10.1242/jeb.36.2.423), [archived](https://web.archive.org/web/20081003122816/http://jeb.biologists.org/cgi/reprint/36/2/423.pdf) 2008-10-03 at the Wayback Machine, retrieved 2008-09-25

1. [Ruppert, Fox & Barnes (2004)](#refRuppert), pp. 523–524

1. [Ruppert, Fox & Barnes (2004)](#refRuppert), pp. 527–528

1. Garwood, Russell J. & Edgecombe, Greg (2011). "Early Terrestrial Animals, Evolution, and Uncertainty". *Evolution: Education and Outreach*. **4** (3): 489–501. [doi:10.1007/s12052-011-0357-y](https://doi.org/10.1007/s12052-011-0357-y)

1. [Ruppert, Fox & Barnes (2004)](#refRuppert), pp. 530, 733

1. [Ruppert, Fox & Barnes (2004)](#refRuppert), pp. 531–532

1. [Ruppert, Fox & Barnes (2004)](#refRuppert), pp. 529–530

1. [Ruppert, Fox & Barnes (2004)](#refRuppert), pp. 532–537

1. [Ruppert, Fox & Barnes (2004)](#refRuppert), pp. 578–580

1. Völkel, R.; Eisner, M.; Weible, K. J. (June 2003). ["Miniaturized imaging systems"](https://web.archive.org/web/20081001225326/http://www.suss-microoptics.com/downloads/Publications/Miniaturized_Imaging_Systems.pdf). *[Microelectronic Engineering](/source/Microelectronic_Engineering)*. **67–68**: 461–472. [doi:10.1016/S0167-9317(03)00102-3](https://doi.org/10.1016/S0167-9317(03)00102-3). Archived from [the original](http://www.suss-microoptics.com/downloads/Publications/Miniaturized_Imaging_Systems.pdf) on 2008-10-01.

1. [Ruppert, Fox & Barnes (2004)](#refRuppert), pp. 537–539

1. Olive, P. J. W. (2001). "Reproduction and Life Cycles in Invertebrates". *Encyclopedia of Life Sciences*. John Wiley & Sons. [doi:10.1038/npg.els.0003649](https://doi.org/10.1038/npg.els.0003649). ISBN 978-0-470-01617-6.

1. Schurko, A. M.; Mazur, D. J.; Logsdon, J. M. (February 2010). "Inventory and phylogenomic distribution of meiotic genes in Nasonia vitripennis and among diverse arthropods". *Insect Molecular Biology*. **19** (Suppl 1): 165–180. [doi:10.1111/j.1365-2583.2009.00948.x](https://doi.org/10.1111/j.1365-2583.2009.00948.x). [PMID 20167026](https://pubmed.ncbi.nlm.nih.gov/20167026). [S2CID 11617147](https://api.semanticscholar.org/CorpusID:11617147)

1. Bernstein, H.; Hopf, F. A.; Michod, R. E. (1987). "The Molecular Basis of the Evolution of Sex". *Molecular Genetics of Development*. Vol. 24. Advances in Genetics. pp. 323–370. [doi:10.1016/s0065-2660(08)60012-7](https://doi.org/10.1016/s0065-2660(08)60012-7). ISBN 978-0-12-017624-3. [PMID 3324702](https://pubmed.ncbi.nlm.nih.gov/3324702)

1. ["Facts About Horseshoe Crabs and FAQ"](https://myfwc.com/research/saltwater/crustaceans/horseshoe-crabs/facts/). Retrieved 2020-01-19.

1. Lourenço, Wilson R. (2002), ["Reproduction in scorpions, with special reference to parthenogenesis"](http://www.european-arachnology.org/proceedings/19th/Lourenco.PDF), *European Arachnology 2000*, Toft, S. & Scharff, N. (eds.), [Aarhus University Press](/source/Aarhus_University_Press), pp. 71–85, ISBN 978-87-7934-001-5, [archived](https://web.archive.org/web/20081003122816/http://www.european-arachnology.org/proceedings/19th/Lourenco.PDF) 2008-10-03 at the Wayback Machine, retrieved 2008-09-28

1. Truman, J. W. & Riddiford, L. M. (September 1999). ["The origins of insect metamorphosis"](http://www.insecta.ufv.br/Entomologia/ent/disciplina/ban%20160/AULAT/aula8/truman.pdf). *[Nature](/source/Nature_(journal))*. **401** (6752): 447–452. [Bibcode:1999Natur.401..447T](https://ui.adsabs.harvard.edu/abs/1999Natur.401..447T). [doi:10.1038/46737](https://doi.org/10.1038/46737). [PMID 10519548](https://pubmed.ncbi.nlm.nih.gov/10519548). [S2CID 4327078](https://api.semanticscholar.org/CorpusID:4327078). [Archived](https://web.archive.org/web/20081003122816/http://www.insecta.ufv.br/Entomologia/ent/disciplina/ban%20160/AULAT/aula8/truman.pdf) 2008-10-03 at the Wayback Machine. Retrieved 2008-09-28.

1. Smith, G., ["Diversity and Adaptations of the Aquatic Insects"](http://faculty.ncf.edu/mccord/pdf/AquaticInsectGeoffSmith.pdf), [New College of Florida](/source/New_College_of_Florida), [archived](https://web.archive.org/web/20081003122816/http://faculty.ncf.edu/mccord/pdf/AquaticInsectGeoffSmith.pdf) 3 October 2008 at the Wayback Machine, retrieved 2008-09-28

1. Bergström, Jan & Hou, Xian-Guang (2005), "Early Palaeozoic non-lamellipedian arthropods", *Crustacea and Arthropod Relationships*, Vol. 16, Crustacean Issues, Stefan Koenemann & Ronald A. Jenner (eds.), Boca Raton: [Taylor & Francis](/source/Taylor_%26_Francis), pp. 73–93, [doi:10.1201/9781420037548.ch4](https://doi.org/10.1201/9781420037548.ch4). ISBN 978-0-8493-3498-6

1. McKeever, Conor (30 September 2016). ["Arthropod ancestor had the mouth of a penis worm"](http://www.nhm.ac.uk/our-science/science-news/2016/september/arthropod-ancestor-mouth.html). *Natural History Museum*. [Archived](https://web.archive.org/web/20170202073340/http://www.nhm.ac.uk/our-science/science-news/2016/september/arthropod-ancestor-mouth.html) 2017-02-02 at the Wayback Machine.

1. Glaessner, M. F. (1958). ["New fossils from the base of the Cambrian in South Australia"](http://www.samuseum.sa.gov.au/Journals/TRSSA/TRSSA_V081/TRSSA_V081_p185p188.pdf). *[Transactions of the Royal Society of South Australia](/source/Transactions_of_the_Royal_Society_of_South_Australia)*. **81**: 185–188. [Archived](https://web.archive.org/web/20081216220102/http://www.samuseum.sa.gov.au/Journals/TRSSA/TRSSA_V081/TRSSA_V081_p185p188.pdf) 2008-12-16 at the Wayback Machine.

1. Lin, J. P.; Gon, S. M.; Gehling, J. G.; Babcock, L. E.; Zhao, Y. L.; Zhang, X. L.; Hu, S. X.; Yuan, J. L.; Yu, M. Y.; Peng, J. (2006). "A *Parvancorina*-like arthropod from the Cambrian of South China". *[Historical Biology](/source/Historical_Biology)*. **18** (1): 33–45. [Bibcode:2006HBio...18...33L](https://ui.adsabs.harvard.edu/abs/2006HBio...18...33L). [doi:10.1080/08912960500508689](https://doi.org/10.1080/08912960500508689). [S2CID 85821717](https://api.semanticscholar.org/CorpusID:85821717)

1. McMenamin, M.A.S (2003), ["*Spriggina* is a trilobitoid ecdysozoan"](http://gsa.confex.com/gsa/2003AM/finalprogram/abstract_62056.htm) (abstract), *[Abstracts with Programs](/source/Abstracts_with_Programs)*. **35** (6): 105, [archived](https://web.archive.org/web/20080830080220/http://gsa.confex.com/gsa/2003AM/finalprogram/abstract_62056.htm) 2008-08-30 at the Wayback Machine, retrieved 2008-10-21

1. Daley, Allison C.; Antcliffe, Jonathan B.; Drage, Harriet B.; Pates, Stephen (2018-05-22). "Early fossil record of Euarthropoda and the Cambrian Explosion". *Proceedings of the National Academy of Sciences of the United States of America*. **115** (21): 5323–5331. [Bibcode:2018PNAS..115.5323D](https://ui.adsabs.harvard.edu/abs/2018PNAS..115.5323D). [doi:10.1073/pnas.1719962115](https://doi.org/10.1073/pnas.1719962115). [PMC 6003487](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6003487). [PMID 29784780](https://pubmed.ncbi.nlm.nih.gov/29784780)

1. Braun, A.; Chen, J.; Waloszek, D.; Maas, A. (2007). ["First Early Cambrian Radiolaria"](http://biosys-serv.biologie.uni-ulm.de/Downloadfolder/PDFs%20Team/2007b_Braun_etal.pdf). *Special Publications*. **286** (1): 143–149. [Bibcode:2007GSLSP.286..143B](https://ui.adsabs.harvard.edu/abs/2007GSLSP.286..143B). [doi:10.1144/SP286.10](https://doi.org/10.1144/SP286.10). [S2CID 129651908](https://api.semanticscholar.org/CorpusID:129651908). [Archived](https://web.archive.org/web/20110718095413/http://biosys-serv.biologie.uni-ulm.de/Downloadfolder/PDFs%20Team/2007b_Braun_etal.pdf) 2011-07-18 at the Wayback Machine.

1. Yuan, X.; Xiao, S.; Parsley, R. L.; Zhou, C.; Chen, Z.; Hu, J. (April 2002). ["Towering sponges in an Early Cambrian Lagerstätte: Disparity between nonbilaterian and bilaterian epifaunal tierers at the Neoproterozoic-Cambrian transition"](https://www.researchgate.net/publication/249520833). *[Geology](/source/Geology_(journal))*. **30** (4): 363–366. [Bibcode:2002Geo....30..363Y](https://ui.adsabs.harvard.edu/abs/2002Geo....30..363Y). [doi:10.1130/0091-7613(2002)030<0363:TSIAEC>2.0.CO;2](https://doi.org/10.1130/0091-7613(2002)030%3C0363:TSIAEC%3E2.0.CO;2)

1. Skovsted, Christian; Brock, Glenn; Paterson, John (2006), ["Bivalved arthropods from the Lower Cambrian Mernmerna Formation of South Australia and their implications for the identification of Cambrian 'small shelly fossils'"](https://www.researchgate.net/publication/303809761), *Association of Australasian Palaeontologists Memoirs*. **32**: 7–41, [ISSN 0810-8889](https://www.worldcat.org/issn/0810-8889)

1. Betts, Marissa; Topper, Timothy; Valentine, James; Skovsted, Christian; Paterson, John; Brock, Glenn (January 2014), ["A new early Cambrian bradoriid (Arthropoda) assemblage from the northern Flinders Ranges, South Australia"](https://www.researchgate.net/publication/236901156), *Gondwana Research*. **25** (1): 420–437, [Bibcode:2014GondR..25..420B](https://ui.adsabs.harvard.edu/abs/2014GondR..25..420B). [doi:10.1016/j.gr.2013.05.007](https://doi.org/10.1016/j.gr.2013.05.007)

1. Lieberman, B. S. (March 1, 1999), ["Testing the Darwinian legacy of the Cambrian radiation using trilobite phylogeny and biogeography"](http://jpaleontol.geoscienceworld.org/cgi/content/abstract/73/2/176), *[Journal of Paleontology](/source/Journal_of_Paleontology)*. **73** (2): 176, [Bibcode:1999JPal...73..176L](https://ui.adsabs.harvard.edu/abs/1999JPal...73..176L). [doi:10.1017/S0022336000027700](https://doi.org/10.1017/S0022336000027700). [S2CID 88588171](https://api.semanticscholar.org/CorpusID:88588171), [archived](https://web.archive.org/web/20081019012441/http://jpaleontol.geoscienceworld.org/cgi/content/abstract/73/2/176) October 19, 2008 at the Wayback Machine, retrieved October 21, 2008

1. ["A 520-million-year-old, five-eyed fossil reveals arthropod origin"](https://phys.org/news/2020-11-million-year-old-five-eyed-fossil-reveals-arthropod.html). *phys.org*. Retrieved 8 December 2020.

1. Zeng, Han; Zhao, Fangchen; Niu, Kecheng; Zhu, Maoyan; Huang, Diying (December 2020). ["An early Cambrian euarthropod with radiodont-like raptorial appendages"](https://www.nature.com/articles/s41586-020-2883-7). *Nature*. **588** (7836): 101–105. [Bibcode:2020Natur.588..101Z](https://ui.adsabs.harvard.edu/abs/2020Natur.588..101Z). [doi:10.1038/s41586-020-2883-7](https://doi.org/10.1038/s41586-020-2883-7). [ISSN 1476-4687](https://www.worldcat.org/issn/1476-4687). [PMID 33149303](https://pubmed.ncbi.nlm.nih.gov/33149303). [S2CID 226248177](https://api.semanticscholar.org/CorpusID:226248177). Retrieved 8 December 2020.

1. Whittington, H. B. (1979). Early arthropods, their appendages and relationships. In M. R. House (Ed.), The origin of major invertebrate groups (pp. 253–268). The Systematics Association Special Volume, 12. London: Academic Press.

1. Whittington, H.B. & Geological Survey of Canada (1985), *The Burgess Shale*, Yale University Press, ISBN 978-0-660-11901-4. [OCLC 15630217](https://www.worldcat.org/oclc/15630217)

1. Gould (1990), p. [page needed].

1. García-Bellido, D. C. & Collins, D. H. (May 2004). "Moulting arthropod caught in the act". *[Nature](/source/Nature_(journal))*. **429** (6987): 40. [Bibcode:2004Natur.429...40G](https://ui.adsabs.harvard.edu/abs/2004Natur.429...40G). [doi:10.1038/429040a](https://doi.org/10.1038/429040a). [PMID 15129272](https://pubmed.ncbi.nlm.nih.gov/15129272). [S2CID 40015864](https://api.semanticscholar.org/CorpusID:40015864)

1. Hegna, Thomas A.; Luque, Javier; Wolfe, Joanna M. (2020-09-10). "The Fossil Record of the Pancrustacea". *Evolution and Biogeography*. Oxford University Press. [doi:10.1093/oso/9780190637842.003.0002](https://doi.org/10.1093/oso/9780190637842.003.0002). ISBN 978-0-19-063784-2.

1. Hou, Xian-Guang; Siveter, Derek J.; Aldridge, Richard J.; Siveter, David J. (2008-10-10). ["Collective Behavior in an Early Cambrian Arthropod"](https://www.science.org/doi/10.1126/science.1162794). *Science*. **322** (5899): 224. [Bibcode:2008Sci...322..224H](https://ui.adsabs.harvard.edu/abs/2008Sci...322..224H). [doi:10.1126/science.1162794](https://doi.org/10.1126/science.1162794). [ISSN 0036-8075](https://www.worldcat.org/issn/0036-8075). [PMID 18845748](https://pubmed.ncbi.nlm.nih.gov/18845748)

1. Budd, G. E.; Butterfield, N. J.; Jensen, S. (December 2001), "Crustaceans and the "Cambrian Explosion"", *[Science](/source/Science_(journal))*. **294** (5549): 2047, [doi:10.1126/science.294.5549.2047a](https://doi.org/10.1126/science.294.5549.2047a). [PMID 11739918](https://pubmed.ncbi.nlm.nih.gov/11739918)

1. Xian-Guang, Hou; Siveter, Derek J.; Aldridge, Richard J.; Siveter, David J. (2009). "A New Arthropod in Chainlike Associations from the Cnengjiang Lagerstätte (Lower Cambrian), Yunnan, China". *Palaeontology*. **52** (4): 951–961. [Bibcode:2009Palgy..52..951X](https://ui.adsabs.harvard.edu/abs/2009Palgy..52..951X). [doi:10.1111/j.1475-4983.2009.00889.x](https://doi.org/10.1111/j.1475-4983.2009.00889.x). [ISSN 0031-0239](https://www.worldcat.org/issn/0031-0239)

1. Zhang, X.-G.; Siveter, D. J.; Waloszek, D.; Maas, A. (October 2007). "An epipodite-bearing crown-group crustacean from the Lower Cambrian". *[Nature](/source/Nature_(journal))*. **449** (7162): 595–598. [Bibcode:2007Natur.449..595Z](https://ui.adsabs.harvard.edu/abs/2007Natur.449..595Z). [doi:10.1038/nature06138](https://doi.org/10.1038/nature06138). [PMID 17914395](https://pubmed.ncbi.nlm.nih.gov/17914395). [S2CID 4329196](https://api.semanticscholar.org/CorpusID:4329196)

1. Pisani, D.; Poling, L. L.; Lyons-Weiler M.; Hedges, S. B. (2004). "The colonization of land by animals: molecular phylogeny and divergence times among arthropods". *[BMC Biology](/source/BMC_Biology)*. **2** (1). [Bibcode:2004BMCB....2....1P](https://ui.adsabs.harvard.edu/abs/2004BMCB....2....1P). [doi:10.1186/1741-7007-2-1](https://doi.org/10.1186/1741-7007-2-1). [PMC 333434](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC333434). [PMID 14731304](https://pubmed.ncbi.nlm.nih.gov/14731304)

1. Cowen, R. (2000). *History of Life*. 3rd ed. Blackwell Science. p. 126. ISBN 978-0-632-04444-3.

1. Braddy, S. J.; Markus Poschmann, M.; & Tetlie, O. E. (2008). "Giant claw reveals the largest ever arthropod". *[Biology Letters](/source/Biology_Letters)*. **4** (1): 106–109. [doi:10.1098/rsbl.2007.0491](https://doi.org/10.1098/rsbl.2007.0491). [PMC 2412931](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2412931). [PMID 18029297](https://pubmed.ncbi.nlm.nih.gov/18029297)

1. Dunlop, J. A. (September 1996). ["A trigonotarbid arachnid from the Upper Silurian of Shropshire"](https://web.archive.org/web/20081216214632/http://palaeontology.palass-pubs.org/pdf/Vol%2039/Pages%20605-614.pdf). *[Palaeontology](/source/Palaeontology_(journal))*. **39** (3): 605–614. Archived from [the original](http://palaeontology.palass-pubs.org/pdf/Vol%2039/Pages%20605-614.pdf) on 2008-12-16.

1. Selden, P. A. & Shear, W. A. (December 2008). "Fossil evidence for the origin of spider spinnerets". *PNAS*. **105** (52): 20781–5. [Bibcode:2008PNAS..10520781S](https://ui.adsabs.harvard.edu/abs/2008PNAS..10520781S). [doi:10.1073/pnas.0809174106](https://doi.org/10.1073/pnas.0809174106). [PMC 2634869](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2634869). [PMID 19104044](https://pubmed.ncbi.nlm.nih.gov/19104044)

1. Selden, P. A. (February 1996). "Fossil mesothele spiders". *[Nature](/source/Nature_(journal))*. **379** (6565): 498–499. [Bibcode:1996Natur.379..498S](https://ui.adsabs.harvard.edu/abs/1996Natur.379..498S). [doi:10.1038/379498b0](https://doi.org/10.1038/379498b0). [S2CID 26323977](https://api.semanticscholar.org/CorpusID:26323977)

1. Vollrath, F. & Selden, P. A. (December 2007). ["The Role of Behavior in the Evolution of Spiders, Silks, and Webs"](http://homepage.mac.com/paulselden/Sites/Website/ARES.pdf). *[Annual Review of Ecology, Evolution, and Systematics](/source/Annual_Review_of_Ecology,_Evolution,_and_Systematics)*. **38** (1): 819–846. [Bibcode:2007AREES..38..819V](https://ui.adsabs.harvard.edu/abs/2007AREES..38..819V). [doi:10.1146/annurev.ecolsys.37.091305.110221](https://doi.org/10.1146/annurev.ecolsys.37.091305.110221). [Archived](https://web.archive.org/web/20081209102852/http://homepage.mac.com/paulselden/Sites/Website/ARES.pdf) 2008-12-09 at the Wayback Machine.

1. Anderson, Evan P.; Schiffbauer, James D.; Jacquet, Sarah M.; Lamsdell, James C.; Kluessendorf, Joanne; Mikulic, Donald G. (2021). "Stranger than a scorpion: a reassessment of Parioscorpio venator, a problematic arthropod from the Llandoverian Waukesha Lagerstätte". *Palaeontology*. **64** (3): 429–474. Zhang, Xi-Guang (ed.). [Bibcode:2021Palgy..64..429A](https://ui.adsabs.harvard.edu/abs/2021Palgy..64..429A). [doi:10.1111/pala.12534](https://doi.org/10.1111/pala.12534). [ISSN 0031-0239](https://www.worldcat.org/issn/0031-0239)

1. Jeram, A. J. (January 1990). "Book-lungs in a Lower Carboniferous scorpion". *[Nature](/source/Nature_(journal))*. **343** (6256): 360–361. [Bibcode:1990Natur.343..360J](https://ui.adsabs.harvard.edu/abs/1990Natur.343..360J). [doi:10.1038/343360a0](https://doi.org/10.1038/343360a0). [S2CID 4327169](https://api.semanticscholar.org/CorpusID:4327169)

1. Howard, Richard J.; Edgecombe, Gregory D.; Legg, David A.; Pisani, Davide; Lozano-Fernandez, Jesus (2019-03-01). "Exploring the evolution and terrestrialization of scorpions (Arachnida: Scorpiones) with rocks and clocks". *Organisms Diversity & Evolution*. **19** (1): 71–86. [Bibcode:2019ODivE..19...71H](https://ui.adsabs.harvard.edu/abs/2019ODivE..19...71H). [doi:10.1007/s13127-019-00390-7](https://doi.org/10.1007/s13127-019-00390-7). [hdl:1983/9ab6548b-b4de-47b5-b1d0-8008d225c375](https://hdl.handle.net/1983/9ab6548b-b4de-47b5-b1d0-8008d225c375). [ISSN 1618-1077](https://www.worldcat.org/issn/1618-1077)

1. Poschmann, Markus; Dunlop, Jason A.; Kamenz, Carsten; Scholtz, Gerhard (December 2008). "The Lower Devonian scorpion *Waeringoscorpio* and the respiratory nature of its filamentous structures, with the description of a new species from the Westerwald area, Germany". *Paläontologische Zeitschrift*. **82** (4): 418–436. [Bibcode:2008PalZ...82..418P](https://ui.adsabs.harvard.edu/abs/2008PalZ...82..418P). [doi:10.1007/BF03184431](https://doi.org/10.1007/BF03184431). [ISSN 0031-0220](https://www.worldcat.org/issn/0031-0220)

1. Engel, M. S. & Grimaldi, D. A. (February 2004). "New light shed on the oldest insect". *[Nature](/source/Nature_(journal))*. **427** (6975): 627–630. [Bibcode:2004Natur.427..627E](https://ui.adsabs.harvard.edu/abs/2004Natur.427..627E). [doi:10.1038/nature02291](https://doi.org/10.1038/nature02291). [PMID 14961119](https://pubmed.ncbi.nlm.nih.gov/14961119). [S2CID 4431205](https://api.semanticscholar.org/CorpusID:4431205)

1. Haug, Carolin & Haug, Joachim T. (2017-05-30). "The presumed oldest flying insect: more likely a myriapod?". *PeerJ*. **5**. [Bibcode:2017PeerJ...5e3402H](https://ui.adsabs.harvard.edu/abs/2017PeerJ...5e3402H). [doi:10.7717/peerj.3402](https://doi.org/10.7717/peerj.3402). [PMC 5452959](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5452959). [PMID 28584727](https://pubmed.ncbi.nlm.nih.gov/28584727)

1. Labandeira, C. & Eble, G. J. (2000). ["The Fossil Record of Insect Diversity and Disparity"](http://www.santafe.edu/research/publications/workingpapers/00-08-044.pdf). *Gondwana Alive: Biodiversity and the Evolving Biosphere*. Anderson, J.; Thackeray, F.; van Wyk, B.; de Wit, M. (eds.). [Witwatersrand University Press](/source/Witwatersrand_University_Press). [Archived](https://web.archive.org/web/20080911075353/http://www.santafe.edu/research/publications/workingpapers/00-08-044.pdf) 2008-09-11 at the Wayback Machine. Retrieved 2008-10-21.

1. Gillott, C. (1995). *Entomology*. Springer. pp. 17–19. ISBN 978-0-306-44967-3.

1. Budd, G.E. (1996). "The morphology of *Opabinia regalis* and the reconstruction of the arthropod stem-group". *[Lethaia](/source/Lethaia)*. **29** (1): 1–14. [Bibcode:1996Letha..29....1B](https://ui.adsabs.harvard.edu/abs/1996Letha..29....1B). [doi:10.1111/j.1502-3931.1996.tb01831.x](https://doi.org/10.1111/j.1502-3931.1996.tb01831.x)

1. Adrain, J. (15 March 1999). ["*Arthropod Fossils and Phylogeny*, edited by Gregory D. Edgecomb"](http://palaeo-electronica.org/1999_1/books/arthropo.htm). [Palaeontologia Electronica](/source/Palaeontologia_Electronica). [Archived](https://web.archive.org/web/20080908053500/http://palaeo-electronica.org/1999_1/books/arthropo.htm) 8 September 2008 at the Wayback Machine. Retrieved 2008-09-28. : The book is Labandiera, Conrad C. & Edgecombe, Gregory (1998). "Arthropod Fossils and Phylogeny". *PALAIOS*. **14** (4): 347. G.D. (ed.). [Columbia University Press](/source/Columbia_University_Press). [Bibcode:1999Palai..14..405L](https://ui.adsabs.harvard.edu/abs/1999Palai..14..405L). [doi:10.2307/3515467](https://doi.org/10.2307/3515467). [JSTOR 3515467](https://www.jstor.org/stable/3515467)

1. Chen, J.-Y.; Edgecombe, G. D.; Ramsköld, L.; Zhou, G.-Q. (2 June 1995). "Head segmentation in Early Cambrian *Fuxianhuia*: implications for arthropod evolution". *[Science](/source/Science_(journal))*. **268** (5215): 1339–1343. [Bibcode:1995Sci...268.1339C](https://ui.adsabs.harvard.edu/abs/1995Sci...268.1339C). [doi:10.1126/science.268.5215.1339](https://doi.org/10.1126/science.268.5215.1339). [PMID 17778981](https://pubmed.ncbi.nlm.nih.gov/17778981). [S2CID 32142337](https://api.semanticscholar.org/CorpusID:32142337)

1. Budd, G. E. (1993). "A Cambrian gilled lobopod from Greenland". *[Nature](/source/Nature_(journal))*. **364** (6439): 709–711. [Bibcode:1993Natur.364..709B](https://ui.adsabs.harvard.edu/abs/1993Natur.364..709B). [doi:10.1038/364709a0](https://doi.org/10.1038/364709a0). [S2CID 4341971](https://api.semanticscholar.org/CorpusID:4341971)

1. Nielsen, C. (2001). [*Animal Evolution: Interrelationships of the living phyla*](https://books.google.com/books?id=UmCg6c0HkqMC&q=nielsen+panarthropoda+euarthropoda&pg=PA194). 2nd ed. [Oxford University Press](/source/Oxford_University_Press). pp. 194–196. ISBN 978-0-19-850681-2.

1. Hou, X.-G.; Bergström, J.; Jie, Y. (2006). "Distinguishing anomalocaridids from arthropods and priapulids". *[Geological Journal](/source/Geological_Journal)*. **41** (3–4): 259–269. [Bibcode:2006GeolJ..41..259X](https://ui.adsabs.harvard.edu/abs/2006GeolJ..41..259X). [doi:10.1002/gj.1050](https://doi.org/10.1002/gj.1050). [S2CID 83582128](https://api.semanticscholar.org/CorpusID:83582128)

1. ["Misunderstood worm-like fossil finds its place in the Tree of Life"](http://www.cam.ac.uk/research/news/misunderstood-worm-like-fossil-finds-its-place-in-the-tree-of-life). [Cambridge University](/source/Cambridge_University). 17 August 2014. [Archived](https://web.archive.org/web/20170107150001/http://www.cam.ac.uk/research/news/misunderstood-worm-like-fossil-finds-its-place-in-the-tree-of-life) 7 January 2017 at the Wayback Machine. Retrieved 24 January 2017.

1. Schmidt-Rhaesa, A.; Bartolomaeus, T.; Lemburg, C.; Ehlers, U.; Garey, J.R. (January 1999). "The position of the Arthropoda in the phylogenetic system". *[Journal of Morphology](/source/Journal_of_Morphology)*. **238** (3): 263–285. [doi:10.1002/(SICI)1097-4687(199812)238:3<263::AID-JMOR1>3.0.CO;2-L](https://doi.org/10.1002/(SICI)1097-4687(199812)238:3%3C263::AID-JMOR1%3E3.0.CO;2-L). [PMID 29852696](https://pubmed.ncbi.nlm.nih.gov/29852696). [S2CID 46920478](https://api.semanticscholar.org/CorpusID:46920478)

1. Telford, M.J.; Bourlat, S.J.; Economou, A.; Papillon, D.; Rota-Stabelli, O. (January 2008). "The evolution of the Ecdysozoa". *[Philosophical Transactions of the Royal Society B: Biological Sciences](/source/Philosophical_Transactions_of_the_Royal_Society_B:_Biological_Sciences)*. **363** (1496): 1529–1537. [doi:10.1098/rstb.2007.2243](https://doi.org/10.1098/rstb.2007.2243). [PMC 2614232](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2614232). [PMID 18192181](https://pubmed.ncbi.nlm.nih.gov/18192181)

1. Ortega-Hernández, Javier (2016). "Making sense of 'lower' and 'upper' stem-group Euarthropoda, with comments on the strict use of the name Arthropoda von Siebold, 1848". *[Biological Reviews](/source/Biological_Reviews)*. **91** (1): 255–273. [Bibcode:2016BioRv..91..255O](https://ui.adsabs.harvard.edu/abs/2016BioRv..91..255O). [doi:10.1111/brv.12168](https://doi.org/10.1111/brv.12168). [PMID 25528950](https://pubmed.ncbi.nlm.nih.gov/25528950). [S2CID 7751936](https://api.semanticscholar.org/CorpusID:7751936)

1. Gregory D. Edgecombe (2020). "Arthropod Origins: Integrating Paleontological and Molecular Evidence". *Annu. Rev. Ecol. Evol. Syst.*. **51**: 1–25. [doi:10.1146/annurev-ecolsys-011720-124437](https://doi.org/10.1146/annurev-ecolsys-011720-124437). [S2CID 225478171](https://api.semanticscholar.org/CorpusID:225478171)

1. Aria, Cédric (2022-04-26). ["The origin and early evolution of arthropods"](http://paleorxiv.org/4zmey/). *Biological Reviews*. **97** (5): 1786–1809. [Bibcode:2022BioRv..97.1786A](https://ui.adsabs.harvard.edu/abs/2022BioRv..97.1786A). [doi:10.1111/brv.12864](https://doi.org/10.1111/brv.12864). [ISSN 1464-7931](https://www.worldcat.org/issn/1464-7931). [PMID 35475316](https://pubmed.ncbi.nlm.nih.gov/35475316). [S2CID 243269510](https://api.semanticscholar.org/CorpusID:243269510)

1. Jenner, R. A. (April 2006). "Challenging received wisdoms: Some contributions of the new microscopy to the new animal phylogeny". *[Integrative and Comparative Biology](/source/Integrative_and_Comparative_Biology)*. **46** (2): 93–103. [doi:10.1093/icb/icj014](https://doi.org/10.1093/icb/icj014). [PMID 21672726](https://pubmed.ncbi.nlm.nih.gov/21672726)

1. Dunlop, Jason A. (31 January 2011). ["Fossil Focus: Chelicerata"](https://www.palaeontologyonline.com/?p=327). *Palaeontology Online*. **1**: 1–8.

1. Liu, Cong; Pates, Stephen; Zhang, Mingjing; Wu, Yu; Ma, Jiaxin; Fu, Dongjing; Zhang, Xingliang (2026-03-21). ["3D morphology of the Cambrian bivalved arthropod Sunella informs about head segmentation, arthrodization, and arthropodization"](https://www.nature.com/articles/s42003-026-09909-z). *Communications Biology*. [doi:10.1038/s42003-026-09909-z](https://doi.org/10.1038/s42003-026-09909-z). [ISSN 2399-3642](https://www.worldcat.org/issn/2399-3642)

1. Ortega-Hernández, Javier (February 2016). ["Making sense of 'lower' and 'upper' stem-group Euarthropoda, with comments on the strict use of the name Arthropoda von Siebold, 1848"](https://onlinelibrary.wiley.com/doi/10.1111/brv.12168). *Biological Reviews*. **91** (1): 255–273. [Bibcode:2016BioRv..91..255O](https://ui.adsabs.harvard.edu/abs/2016BioRv..91..255O). [doi:10.1111/brv.12168](https://doi.org/10.1111/brv.12168). [ISSN 1464-7931](https://www.worldcat.org/issn/1464-7931). [PMID 25528950](https://pubmed.ncbi.nlm.nih.gov/25528950)

1. Pates, S.; Botting, J. P.; Muir, L. A.; Wolfe, J. M. (2022). "Ordovician opabiniid-like animals and the role of the proboscis in euarthropod head evolution". *Nature Communications*. **13** (1): 6969. [Bibcode:2022NatCo..13.6969P](https://ui.adsabs.harvard.edu/abs/2022NatCo..13.6969P). [doi:10.1038/s41467-022-34204-w](https://doi.org/10.1038/s41467-022-34204-w). [PMC 9666559](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9666559). [PMID 36379946](https://pubmed.ncbi.nlm.nih.gov/36379946)

1. Liu, Jianni; Dunlop, Jason A.; Steiner, Michael; Shu, Degan (2022-07-22). "A Cambrian fossil from the Chengjiang fauna sharing characteristics with gilled lobopodians, opabiniids and radiodonts". *Frontiers in Earth Science*. **10**. [doi:10.3389/feart.2022.861934](https://doi.org/10.3389/feart.2022.861934). [ISSN 2296-6463](https://www.worldcat.org/issn/2296-6463)

1. Berks, H. O.; Lunde Nielsen, M.; Flannery-Sutherland, J.; Thorshøj Nielsen, A.; Park, T.-Y. S.; Vinther, J. (2023). "A possibly deep branching artiopodan arthropod from the lower Cambrian Sirius Passet Lagerstätte (North Greenland)". *Papers in Palaeontology*. **9** (3). [Bibcode:2023PPal....9E1495B](https://ui.adsabs.harvard.edu/abs/2023PPal....9E1495B). [doi:10.1002/spp2.1495](https://doi.org/10.1002/spp2.1495)

1. Moysiuk J, Caron JB (January 2019). "Burgess Shale fossils shed light on the agnostid problem". *Proceedings. Biological Sciences*. **286** (1894). [doi:10.1098/rspb.2018.2314](https://doi.org/10.1098/rspb.2018.2314). [PMC 6367181](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6367181). [PMID 30963877](https://pubmed.ncbi.nlm.nih.gov/30963877)

1. O'Flynn, Robert J.; Audo, Denis; Williams, Mark; Zhai, Dayou; Chen, Hong; Liu, Yu (5 August 2020). ["A new euarthropod with 'great appendage'-like frontal head limbs from the Chengjiang Lagerstätte, Southwest China"](https://palaeo-electronica.org/content/2020/3115-a-new-cambrian-euarthropod). *Palaeontologia Electronica*. **23** (2): 1–23. [doi:10.26879/1069](https://doi.org/10.26879/1069). [ISSN 1094-8074](https://www.worldcat.org/issn/1094-8074). [S2CID 221565910](https://api.semanticscholar.org/CorpusID:221565910)

1. Fu, D.; Legg, D. A.; Daley, A. C.; Budd, G. E.; Wu, Y.; Zhang, X. (2022). "The evolution of biramous appendages revealed by a carapace-bearing Cambrian arthropod". *Philosophical Transactions of the Royal Society B: Biological Sciences*. **377** (1847). [doi:10.1098/rstb.2021.0034](https://doi.org/10.1098/rstb.2021.0034). [PMC 8819368](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8819368). [PMID 35125000](https://pubmed.ncbi.nlm.nih.gov/35125000)

1. O'Flynn, Robert J.; Williams, Mark; Yu, Mengxiao; Harvey, Thomas; Liu, Yu (2022). ["A new euarthropod with large frontal appendages from the early Cambrian Chengjiang biota"](https://palaeo-electronica.org/content/2022/3551-a-new-chengjiang-euarthropod). *Palaeontologia Electronica*. **25** (1): 1–21. [doi:10.26879/1167](https://doi.org/10.26879/1167). [S2CID 246779634](https://api.semanticscholar.org/CorpusID:246779634)

1. Zhang, Caixia; Liu, Yu; Ortega-Hernández, Javier; Wolfe, Joanna; Jin, Changfei; Mai, Huijuan; Hou, Xian-guang; Guo, Jin; Zhai, Dayou (19 April 2023). "Three-dimensional morphology of the biramous appendages in Isoxys from the early Cambrian of South China, and its implications for early euarthropod evolution". *Proceedings of the Royal Society B: Biological Sciences*. **290** (1997). [doi:10.1098/rspb.2023.0335](https://doi.org/10.1098/rspb.2023.0335). [PMC 10113025](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10113025). [PMID 37072042](https://pubmed.ncbi.nlm.nih.gov/37072042)

1. Moysiuk, Joseph; Izquierdo-López, Alejandro; Kampouris, George E.; Caron, Jean-Bernard (July 2022). "A new marrellomorph arthropod from southern Ontario: a rare case of soft-tissue preservation on a Late Ordovician open marine shelf". *Journal of Paleontology*. **96** (4): 859–874. [Bibcode:2022JPal...96..859M](https://ui.adsabs.harvard.edu/abs/2022JPal...96..859M). [doi:10.1017/jpa.2022.11](https://doi.org/10.1017/jpa.2022.11). [ISSN 0022-3360](https://www.worldcat.org/issn/0022-3360)

1. Zhai, Dayou; Williams, Mark; Siveter, David J.; Harvey, Thomas H. P.; Sansom, Robert S.; Gabbott, Sarah E.; Siveter, Derek J.; Ma, Xiaoya; Zhou, Runqing; Liu, Yu; Hou, Xianguang (2019-09-03). "Variation in appendages in early Cambrian bradoriids reveals a wide range of body plans in stem-euarthropods". *Communications Biology*. **2** (1): 329. [doi:10.1038/s42003-019-0573-5](https://doi.org/10.1038/s42003-019-0573-5). [ISSN 2399-3642](https://www.worldcat.org/issn/2399-3642). [PMC 6722085](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6722085). [PMID 31508504](https://pubmed.ncbi.nlm.nih.gov/31508504)

1. Liu, Yu; Ortega-Hernández, Javier; Zhai, Dayou; Hou, Xianguang (August 2020). "A Reduced Labrum in a Cambrian Great-Appendage Euarthropod". *Current Biology*. **30** (15): 3057–3061.e2. [Bibcode:2020CBio...30E3057L](https://ui.adsabs.harvard.edu/abs/2020CBio...30E3057L). [doi:10.1016/j.cub.2020.05.085](https://doi.org/10.1016/j.cub.2020.05.085). [PMID 32589912](https://pubmed.ncbi.nlm.nih.gov/32589912)

1. Lamsdell, James C. (2012-12-18). "Revised systematics of Palaeozoic 'horseshoe crabs' and the myth of monophyletic Xiphosura". *Zoological Journal of the Linnean Society*. **167** (1): 1–27. [doi:10.1111/j.1096-3642.2012.00874.x](https://doi.org/10.1111/j.1096-3642.2012.00874.x). [ISSN 0024-4082](https://www.worldcat.org/issn/0024-4082)

1. Legg, David A.; Sutton, Mark D.; Edgecombe, Gregory D. (2013-09-30). "Arthropod fossil data increase congruence of morphological and molecular phylogenies". *Nature Communications*. **4** (1): 2485. [Bibcode:2013NatCo...4.2485L](https://ui.adsabs.harvard.edu/abs/2013NatCo...4.2485L). [doi:10.1038/ncomms3485](https://doi.org/10.1038/ncomms3485). [ISSN 2041-1723](https://www.worldcat.org/issn/2041-1723). [PMID 24077329](https://pubmed.ncbi.nlm.nih.gov/24077329)

1. Aria, C.; Zhao, F.; Zhu, M. (2021). "Fuxianhuiids are mandibulates and share affinities with total-group Myriapoda". *Journal of the Geological Society*. **178** (5). [Bibcode:2021JGSoc.178..246A](https://ui.adsabs.harvard.edu/abs/2021JGSoc.178..246A). [doi:10.1144/jgs2020-246](https://doi.org/10.1144/jgs2020-246). [S2CID 233952670](https://api.semanticscholar.org/CorpusID:233952670)

1. Izquierdo-López, Alejandro & Caron, Jean-Bernard (August 2024). "The Cambrian Odaraia alata and the colonization of nektonic suspension-feeding niches by early mandibulates". *Proceedings of the Royal Society B: Biological Sciences*. **291** (2027). [doi:10.1098/rspb.2024.0622](https://doi.org/10.1098/rspb.2024.0622). [ISSN 1471-2954](https://www.worldcat.org/issn/1471-2954). [PMC 11463219](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11463219). [PMID 39043240](https://pubmed.ncbi.nlm.nih.gov/39043240)

1. Edgecombe, Gregory D.; Strullu-Derrien, Christine; Góral, Tomasz; Hetherington, Alexander J.; Thompson, Christine; Koch, Marcus (2020). "Aquatic stem group myriapods close a gap between molecular divergence dates and terrestrial fossil record". *Proceedings of the National Academy of Sciences*. **117** (16): 8966–8972. [Bibcode:2020PNAS..117.8966E](https://ui.adsabs.harvard.edu/abs/2020PNAS..117.8966E). [doi:10.1073/pnas.1920733117](https://doi.org/10.1073/pnas.1920733117). [PMC 7183169](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7183169). [PMID 32253305](https://pubmed.ncbi.nlm.nih.gov/32253305). [S2CID 215408474](https://api.semanticscholar.org/CorpusID:215408474)

1. Pulsipher, M. A.; Anderson, E. P.; Wright, L. S.; Kluessendorf, J.; Mikulic, D. G.; Schiffbauer, J. D. (2022). "Description of *Acheronauta* gen. nov., a possible mandibulate from the Silurian Waukesha Lagerstätte, Wisconsin, USA". *Journal of Systematic Palaeontology*. **20** (1): 2109216. [Bibcode:2022JSPal..20....1P](https://ui.adsabs.harvard.edu/abs/2022JSPal..20....1P). [doi:10.1080/14772019.2022.2109216](https://doi.org/10.1080/14772019.2022.2109216). [S2CID 252839113](https://api.semanticscholar.org/CorpusID:252839113)

1. Bernot, James P; Owen, Christopher L; Wolfe, Joanna M; Meland, Kenneth; Olesen, Jørgen; Crandall, Keith A (2023-08-03). ["Major Revisions in Pancrustacean Phylogeny and Evidence of Sensitivity to Taxon Sampling"](https://academic.oup.com/mbe/article/doi/10.1093/molbev/msad175/7239260). *Molecular Biology and Evolution*. **40** (8). Pupko, Tal (ed.). [doi:10.1093/molbev/msad175](https://doi.org/10.1093/molbev/msad175). [ISSN 0737-4038](https://www.worldcat.org/issn/0737-4038). [PMC 10414812](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10414812). [PMID 37552897](https://pubmed.ncbi.nlm.nih.gov/37552897)

1. Clark, Neil D L; Feldmann, Rodney M; Schram, Frederick R; Schweitzer, Carrie E (2020). ["Redescription of *Americlus rankini* (Woodward, 1868) (Pancrustacea: Cyclida: Americlidae) and interpretation of its systematic placement, morphology, and paleoecology"](https://eprints.gla.ac.uk/210399/7/210399.pdf). *Journal of Crustacean Biology*. **40** (2): 181–193. [doi:10.1093/jcbiol/ruaa001](https://doi.org/10.1093/jcbiol/ruaa001)

1. Peel, J.S. & Stein, M. ["A new Arthropod from the Lower Cambrian Sirius Passet Fossil-Lagerstätten of North Greenland"](http://www.geology.cz/bulletin/contents/2009/vol84no4/1158_peel.pdf). *Bulletin of Geosciences*. **84** (4): 1158.

1. Wilson, Heather M. & Almond, John E. (February 2001). "New Euthycarcinoids and an Enigmatic Arthropod from the British Coal Measures". *Palaeontology*. **44** (1): 143–156. [Bibcode:2001Palgy..44..143W](https://ui.adsabs.harvard.edu/abs/2001Palgy..44..143W). [doi:10.1111/1475-4983.00174](https://doi.org/10.1111/1475-4983.00174)

1. Fayers, S. R.; Trewin, N. H.; Morrissey, L. (May 2010). "A large arthropod from the Lower Old Red Sandstone (Early Devonian) of Tredomen Quarry, south Wales: ARTHROPOD FROM THE LOWER ORS". *Palaeontology*. **53** (3): 627–643. [doi:10.1111/j.1475-4983.2010.00951.x](https://doi.org/10.1111/j.1475-4983.2010.00951.x)

1. Lin, Jih-Pai (2009-06-23). "Function and hydrostatics in the telson of the Burgess Shale arthropod Burgessia". *Biology Letters*. **5** (3): 376–379. [doi:10.1098/rsbl.2008.0740](https://doi.org/10.1098/rsbl.2008.0740). [ISSN 1744-9561](https://www.worldcat.org/issn/1744-9561). [PMC 2679911](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2679911). [PMID 19324649](https://pubmed.ncbi.nlm.nih.gov/19324649)

1. Waloszek, Dieter & Müller, Klaus (1990-10-01). ["Upper Cambrian stem-lineage crustaceans and their bearing upon the monophyly of Crustacea and the position of Agnostus"](https://www.researchgate.net/publication/280025168). *Lethaia*. **23**: 409–427. [doi:10.1111/j.1502-3931.1990.tb01373.x](https://doi.org/10.1111/j.1502-3931.1990.tb01373.x)

1. Robison, Richard A. (January 1990). "Earliest-known uniramous arthropod". *Nature*. **343** (6254): 163–164. [Bibcode:1990Natur.343..163R](https://ui.adsabs.harvard.edu/abs/1990Natur.343..163R). [doi:10.1038/343163a0](https://doi.org/10.1038/343163a0)

1. Garwood, R. & Sutton, M. (18 February 2012), ["The enigmatic arthropod Camptophyllia"](http://palaeo-electronica.org/content/pdfs/268.pdf/), *Palaeontologia Electronica*. **15** (2): 12, [Bibcode:2001Palgy..44..143W](https://ui.adsabs.harvard.edu/abs/2001Palgy..44..143W). [doi:10.1111/1475-4983.00174](https://doi.org/10.1111/1475-4983.00174), [archived](https://web.archive.org/web/20131202222600/http://palaeo-electronica.org/content/pdfs/268.pdf) 2 December 2013 at the Wayback Machine, retrieved 11 June 2012

1. Zhai, Dayou; Williams, Mark; Siveter, David J.; Siveter, Derek J.; Harvey, Thomas H. P.; Sansom, Robert S.; Mai, Huijuan; Zhou, Runqing; Hou, Xianguang (2022-02-22). ["Chuandianella ovata: An early Cambrian stem euarthropod with feather-like appendages"](https://palaeo-electronica.org/content/2022/3557-chuandianella-ovata). *Palaeontologia Electronica*. **25** (1): 1–22. [doi:10.26879/1172](https://doi.org/10.26879/1172). [ISSN 1094-8074](https://www.worldcat.org/issn/1094-8074). [S2CID 247123967](https://api.semanticscholar.org/CorpusID:247123967)

1. Gabbott, Sarah E.; Edgecombe, Gregory D.; Theron, Johannes N.; Aldridge, Richard J. (2025). "A new euarthropod from the Soom Shale (Ordovician) Konservat-Lagerstätte, South Africa, with exceptional preservation of the connective endoskeleton and myoanatomy". *Papers in Palaeontology*. **11** (2). [Bibcode:2025PPal...11E0004G](https://ui.adsabs.harvard.edu/abs/2025PPal...11E0004G). [doi:10.1002/spp2.70004](https://doi.org/10.1002/spp2.70004). [ISSN 2056-2802](https://www.worldcat.org/issn/2056-2802)

1. Lerosey-Aubril, Rudy (March 2015). "Notchia weugi gen. et sp. nov.: a new short-headed arthropod from the Weeks Formation Konservat-Lagerstätte (Cambrian; Utah)". *Geological Magazine*. **152** (2): 351–357. [Bibcode:2015GeoM..152..351L](https://ui.adsabs.harvard.edu/abs/2015GeoM..152..351L). [doi:10.1017/S0016756814000375](https://doi.org/10.1017/S0016756814000375)

1. Anderson, Evan P.; Rosbach, Stephanie A.; Pulsipher, Mikaela A.; Mikulic, Donald; Schiffbauer, James D. (16 September 2025). "The 'butterfly animal,' Papiliomaris kluessendorfae n. gen. n. sp.: An enigmatic bivalved arthropod of the Waukesha biota". *Journal of Paleontology*. **99** (4): 818–834. [Bibcode:2025JPal...99..818A](https://ui.adsabs.harvard.edu/abs/2025JPal...99..818A). [doi:10.1017/jpa.2025.10102](https://doi.org/10.1017/jpa.2025.10102)

1. Van Roy, Peter; Rak, Štěpán; Budil, Petr; Fatka, Oldřich (2022-06-13). "Redescription of the cheloniellid euarthropod *Triopus draboviensis* from the Upper Ordovician of Bohemia, with comments on the affinities of *Parioscorpio venator*". *Geological Magazine*. **159** (9): 1471–1489. [Bibcode:2022GeoM..159.1471V](https://ui.adsabs.harvard.edu/abs/2022GeoM..159.1471V). [doi:10.1017/s0016756822000292](https://doi.org/10.1017/s0016756822000292). [hdl:1854/LU-8756253](https://hdl.handle.net/1854/LU-8756253). [ISSN 0016-7568](https://www.worldcat.org/issn/0016-7568). [S2CID 249652930](https://api.semanticscholar.org/CorpusID:249652930)

1. McCoy, Victoria E.; Strother, Paul K.; Briggs, Derek E. G. (November 2012). "A Possible Tracemaker for Arthrophycus Alleghaniensis". *Journal of Paleontology*. **86** (6): 996–1001. [Bibcode:2012JPal...86..996M](https://ui.adsabs.harvard.edu/abs/2012JPal...86..996M). [doi:10.1666/11-133R1.1](https://doi.org/10.1666/11-133R1.1)

1. Anderson, Lyall I. & Trewin, Nigel H. (May 2003). "An Early Devonian arthropod fauna from the Windyfield cherts, Aberdeenshire, Scotland". *Palaeontology*. **46** (3): 467–509. [Bibcode:2003Palgy..46..467A](https://ui.adsabs.harvard.edu/abs/2003Palgy..46..467A). [doi:10.1111/1475-4983.00308](https://doi.org/10.1111/1475-4983.00308)

1. Haug, J.T.; Maas, A.; Haug, C.; Waloszek, D. (2011-11-01). "Sarotrocercus oblitus - Small arthropod with great impact on the understanding of arthropod evolution?". *Bulletin of Geosciences*. [doi:10.3140/bull.geosci.1283](https://doi.org/10.3140/bull.geosci.1283). [ISSN 1802-8225](https://www.worldcat.org/issn/1802-8225)

1. Ortega-Hernández, Javier; Legg, David A.; Braddy, Simon J. (2013). "The phylogeny of aglaspidid arthropods and the internal relationships within Artiopoda". *Cladistics*. **29** (1): 15–45. [Bibcode:2013Cladi..29...15O](https://ui.adsabs.harvard.edu/abs/2013Cladi..29...15O). [doi:10.1111/j.1096-0031.2012.00413.x](https://doi.org/10.1111/j.1096-0031.2012.00413.x). [PMID 34814371](https://pubmed.ncbi.nlm.nih.gov/34814371). [S2CID 85744103](https://api.semanticscholar.org/CorpusID:85744103)

1. Chen, Fei-Yang; Betts, Marissa J.; Zhang, Zhi-Liang; Brock, Glenn A. (2025-06-01). ["The bivalved arthropod Caudicaella aff. bispinata from the Heatherdale Shale (Cambrian Stage 3), South Australia"](https://linkinghub.elsevier.com/retrieve/pii/S1871174X24001161). *Palaeoworld*. **34** (3): 100882. [Bibcode:2025Palae..3400882C](https://ui.adsabs.harvard.edu/abs/2025Palae..3400882C). [doi:10.1016/j.palwor.2024.09.006](https://doi.org/10.1016/j.palwor.2024.09.006). [ISSN 1871-174X](https://www.worldcat.org/issn/1871-174X)

1. Kühl, Gabrielle & Rust, Jes (2009). "*Devonohexapodus bocksbergensis* is a synonym of *Wingertshellicus backesi* (Euarthropoda) – no evidence for marine hexapods living in the Devonian Hunsrück Sea". *Organisms Diversity & Evolution*. **9** (3): 215–231. [Bibcode:2009ODivE...9..215K](https://ui.adsabs.harvard.edu/abs/2009ODivE...9..215K). [doi:10.1016/j.ode.2009.03.002](https://doi.org/10.1016/j.ode.2009.03.002)

1. Pates, Stephen; Lerosey-Aubril, Rudy; Daley, Allison C.; Kier, Carlo; Bonino, Enrico; Ortega-Hernández, Javier (19 January 2021). "The diverse radiodont fauna from the Marjum Formation of Utah, USA (Cambrian: Drumian)". *PeerJ*. **9**. [Bibcode:2021PeerJ...910509P](https://ui.adsabs.harvard.edu/abs/2021PeerJ...910509P). [doi:10.7717/peerj.10509](https://doi.org/10.7717/peerj.10509). [PMC 7821760](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7821760). [PMID 33552709](https://pubmed.ncbi.nlm.nih.gov/33552709)

1. McCoy, Victoria E.; Herrera, Fabiany; Wittry, Jack; Mayer, Paul; Lamsdell, James C. (2025). "A possible vicissicaudatan arthropod from the Late Carboniferous Mazon Creek Lagerstätte". *Geological Magazine*. **162**. [Bibcode:2025GeoM..162E...3M](https://ui.adsabs.harvard.edu/abs/2025GeoM..162E...3M). [doi:10.1017/S001675682400044X](https://doi.org/10.1017/S001675682400044X)

1. Carapelli, Antonio; Liò, Pietro; Nardi, Francesco; van der Wath, Elizabeth; Frati, Francesco (16 August 2007). "Phylogenetic analysis of mitochondrial protein coding genes confirms the reciprocal paraphyly of Hexapoda and Crustacea". *[BMC Evolutionary Biology](/source/BMC_Evolutionary_Biology)*. **7** (Suppl 2): S8. [Bibcode:2007BMCEE...7S...8C](https://ui.adsabs.harvard.edu/abs/2007BMCEE...7S...8C). [doi:10.1186/1471-2148-7-S2-S8](https://doi.org/10.1186/1471-2148-7-S2-S8). [PMC 1963475](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1963475). [PMID 17767736](https://pubmed.ncbi.nlm.nih.gov/17767736)

1. Regier, Jerome C.; Shultz, J. W.; Zwick, A.; Hussey, A.; Ball, B.; Wetzer, R.; Martin, J. W.; Cunningham, C. W. et al. (2010). "Arthropod relationships revealed by phylogenomic analysis of nuclear protein-coding sequences". *[Nature](/source/Nature_(journal))*. **463** (7284): 1079–1084. [Bibcode:2010Natur.463.1079R](https://ui.adsabs.harvard.edu/abs/2010Natur.463.1079R). [doi:10.1038/nature08742](https://doi.org/10.1038/nature08742). [PMID 20147900](https://pubmed.ncbi.nlm.nih.gov/20147900). [S2CID 4427443](https://api.semanticscholar.org/CorpusID:4427443)

1. von Reumont, Bjoern M.; Jenner, Ronald A.; Wills, Matthew A.; Dell'Ampio, Emiliano; Pass, Günther; Ebersberger, Ingo; Meyer, Benjamin; Koenemann, Stefan; Iliffe, Thomas M.; Stamatakis, Alexandros; Niehuis, Oliver; Meusemann, Karen; Misof, Bernhard (2011). "Pancrustacean phylogeny in the light of new phylogenomic data: support for Remipedia as the possible sister group of Hexapoda". *Molecular Biology and Evolution*. **29** (3): 1031–45. [doi:10.1093/molbev/msr270](https://doi.org/10.1093/molbev/msr270). [PMID 22049065](https://pubmed.ncbi.nlm.nih.gov/22049065)

1. Hassanin, Alexandre (2006). ["Phylogeny of Arthropoda inferred from mitochondrial sequences: Strategies for limiting the misleading effects of multiple changes in pattern and rates of substitution"](http://www.csulb.edu/~dlunderw/entomology/Arthropodphylogeny2006.pdf). *[Molecular Phylogenetics and Evolution](/source/Molecular_Phylogenetics_and_Evolution)*. **38** (1): 100–116. [Bibcode:2006MolPE..38..100H](https://ui.adsabs.harvard.edu/abs/2006MolPE..38..100H). [doi:10.1016/j.ympev.2005.09.012](https://doi.org/10.1016/j.ympev.2005.09.012). [PMID 16290034](https://pubmed.ncbi.nlm.nih.gov/16290034). [Archived](https://web.archive.org/web/20110110023714/http://www.csulb.edu/~dlunderw/entomology/Arthropodphylogeny2006.pdf) 2011-01-10 at the Wayback Machine. Retrieved 2010-04-16.

1. Giribet, G.; Richter, S.; Edgecombe, G. D.; Wheeler, W. C. (2005). [*The position of crustaceans within Arthropoda – Evidence from nine molecular loci and morphology*](http://www.amonline.net.au/palaeontology/pdf/giribet-etal2005.pdf). Vol. 16. Crustacean Issues. pp. 307–352. [doi:10.1201/9781420037548.ch13](https://doi.org/10.1201/9781420037548.ch13). ISBN 978-0-8493-3498-6. [Archived](https://web.archive.org/web/20060916153440/https://www.amonline.net.au/palaeontology/pdf/giribet-etal2005.pdf) 2006-09-16 at the Wayback Machine. Retrieved 2006-08-23.

1. Schwentner, Martin; Combosch, David; Nelson, Joey; Giribet, Gonzalo (19 June 2017). "A Phylogenomic Solution to the Origin of Insects by Resolving Crustacean-Hexapod Relationships". *Current Biology*. **27** (12): 1818–1824.e5. [Bibcode:2017CBio...27E1818S](https://ui.adsabs.harvard.edu/abs/2017CBio...27E1818S). [doi:10.1016/j.cub.2017.05.040](https://doi.org/10.1016/j.cub.2017.05.040). [PMID 28602656](https://pubmed.ncbi.nlm.nih.gov/28602656)

1. Lozano-Fernandez, Jesus; Giacomelli, Mattia; Fleming, James F.; Chen, Albert; Vinther, Jakob; Thomsen, Philip Francis; Glenner, Henrik; Palero, Ferran; Legg, David A.; Iliffe, Thomas M.; Pisani, Davide; Olesen, Jørgen (2019). "Pancrustacean Evolution Illuminated by Taxon-Rich GenomicScale Data Sets with an Expanded Remipede Sampling". *Genome Biol. Evol.*. **11** (8): 2055–2070. [doi:10.1093/gbe/evz097](https://doi.org/10.1093/gbe/evz097). [PMC 6684935](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6684935). [PMID 31270537](https://pubmed.ncbi.nlm.nih.gov/31270537)

1. Giribet, Gonzalo & Edgecombe, Gregory (June 2019). "The Phylogeny and Evolutionary History of Arthropods". *Current Biology*. **29** (12): R592–R602. [Bibcode:2019CBio...29.R592G](https://ui.adsabs.harvard.edu/abs/2019CBio...29.R592G). [doi:10.1016/j.cub.2019.04.057](https://doi.org/10.1016/j.cub.2019.04.057). [PMID 31211983](https://pubmed.ncbi.nlm.nih.gov/31211983). [S2CID 189926344](https://api.semanticscholar.org/CorpusID:189926344)

1. Misof, Bernhard et al. (2014). "Phylogenomics resolves the timing and pattern of insect evolution". *Science*. **346** (6210): 763–767. [Bibcode:2014Sci...346..763M](https://ui.adsabs.harvard.edu/abs/2014Sci...346..763M). [doi:10.1126/science.1257570](https://doi.org/10.1126/science.1257570). [PMID 25378627](https://pubmed.ncbi.nlm.nih.gov/25378627). [S2CID 36008925](https://api.semanticscholar.org/CorpusID:36008925)

1. Wickins, J. F. & Lee, D. O'C. (2002). [*Crustacean Farming: Ranching and Culture*](http://www.blackwellpublishing.com/book.asp?ref=9780632054640). 2nd ed. Blackwell. ISBN 978-0-632-05464-0. [Archived](https://web.archive.org/web/20081206015234/http://www.blackwellpublishing.com/book.asp?ref=9780632054640) 2008-12-06 at the Wayback Machine. Retrieved 2008-10-03.

1. Bailey, S., ["Bugfood II: Insects as Food!?!"](http://www.uky.edu/Ag/Entomology/ythfacts/bugfood/bugfood2.htm), University of Kentucky Department of Entomology, [archived](https://web.archive.org/web/20081216224319/http://www.uky.edu/Ag/Entomology/ythfacts/bugfood/bugfood2.htm) 2008-12-16 at the Wayback Machine, retrieved 2008-10-03

1. Unger, L., ["Bugfood III: Insect Snacks from Around the World"](http://www.uky.edu/Ag/Entomology/ythfacts/bugfood/yf813.htm), University of Kentucky Department of Entomology, [archived](https://web.archive.org/web/20081010124417/http://www.uky.edu/Ag/Entomology/ythfacts/bugfood/yf813.htm) 10 October 2008 at the Wayback Machine, retrieved 2008-10-03

1. Rigby, R. (September 21, 2002), ["Tuck into a Tarantula"](http://www.rhymer.net/cutsE.htm), *[The Sunday Telegraph](/source/The_Sunday_Telegraph)*, [archived](https://web.archive.org/web/20090718173613/http://www.rhymer.net/cutsE.htm) July 18, 2009 at the Wayback Machine, retrieved 2009-08-24

1. ["Spiderwomen serve up Cambodia's creepy caviar"](http://abc.net.au/news/indepth/featureitems/s664704.htm), *ABC News Online*, September 2, 2002, [archived](https://web.archive.org/web/20080603171942/http://www.abc.net.au/news/indepth/featureitems/s664704.htm) June 3, 2008 at the Wayback Machine, retrieved 2009-08-24

1. Ray, N. (2002). *Lonely Planet Cambodia*. Lonely Planet Publications. p. 308. ISBN 978-1-74059-111-9.

1. Weil, C. (2006), [*Fierce Food*](https://archive.org/details/fiercefoodintrep0000weil), Plume, ISBN 978-0-452-28700-6, [archived](https://web.archive.org/web/20110511192407/http://www.budgettravel.com/bt-dyn/content/article/2006/10/24/AR2006102400797.html) 2011-05-11 at the Wayback Machine, retrieved 2008-10-03

1. Taylor, R. L. (1975), "Butterflies in My Stomach (or: Insects in Human Nutrition)", Woodbridge Press Publishing Company, [Santa Barbara, California](/source/Santa_Barbara,_California)

1. Paoletti, M. G. (2005), [*Ecological implications of minilivestock: potential of insects, rodents, frogs, and snails*](https://books.google.com/books?id=u4eTQgAACAAJ), [Science Publishers](/source/Science_Publishers), p. 648, ISBN 978-1-57808-339-8

1. Gallai, N.; Salles, J.-M.; Settele, J.; Vaissière, B. E. (August 2008). ["Economic valuation of the vulnerability of world agriculture confronted with pollinator decline"](https://halshs.archives-ouvertes.fr/halshs-01293686/file/Gallai%20et%20al.%202009%20Ecological%20Economics%20Economic%20Valiuation%20of%20Poll.pdf). *[Ecological Economics](/source/Ecological_Economics_(journal))*. **68** (3): 810–821. [doi:10.1016/j.ecolecon.2008.06.014](https://doi.org/10.1016/j.ecolecon.2008.06.014). [S2CID 54818498](https://api.semanticscholar.org/CorpusID:54818498). [Archived](https://web.archive.org/web/20190427184211/https://halshs.archives-ouvertes.fr/halshs-01293686/file/Gallai%20et%20al.%202009%20Ecological%20Economics%20Economic%20Valiuation%20of%20Poll.pdf) 2019-04-27 at the Wayback Machine. Retrieved 2018-11-24. Free summary at Gallai, N.; Salles, J.; Settele, J.; Vaissiere, B. (2009). ["Economic value of insect pollination worldwide estimated at 153 billion euros"](http://www.eurekalert.org/pub_releases/2008-09/haog-evo091508.php). *Ecological Economics*. **68** (3): 810–821. [doi:10.1016/j.ecolecon.2008.06.014](https://doi.org/10.1016/j.ecolecon.2008.06.014). [S2CID 54818498](https://api.semanticscholar.org/CorpusID:54818498). [Archived](https://web.archive.org/web/20081203135146/http://www.eurekalert.org/pub_releases/2008-09/haog-evo091508.php) 2008-12-03 at the Wayback Machine. Retrieved 2008-10-03.

1. ["Apiservices — International honey market — World honey production, imports & exports"](http://www.beekeeping.com/databases/honey-market/world_honey.htm), [archived](https://web.archive.org/web/20081206043600/http://www.beekeeping.com/databases/honey-market/world_honey.htm) 2008-12-06 at the Wayback Machine, retrieved 2008-10-03

1. ["Time line of fabrics"](http://threadsintyme.tripod.com/id63.htm), Threads In Tyme, LTD, [archived](https://web.archive.org/web/20051028155009/http://threadsintyme.tripod.com/id63.htm) October 28, 2005 at the Wayback Machine, retrieved 2005-07-14

1. Jeff Behan, ["The bug that changed history"](http://www.gcrg.org/bqr/8-2/bug.htm), [archived](https://web.archive.org/web/20060621103349/http://gcrg.org/bqr/8-2/bug.htm) 21 June 2006 at the Wayback Machine, retrieved 2006-06-26

1. ["Canary Islands cochineal producers homepage"](http://www.arrakis.es/~rpdeblas/cochinea.htm), [archived](https://web.archive.org/web/20050624075803/http://www.arrakis.es/~rpdeblas/cochinea.htm) 24 June 2005 at the Wayback Machine, retrieved 2005-07-14

1. Hall, R. D. & Castner, J. L. (2000), ["Introduction"](https://archive.org/details/forensicentomolo0000unse/page/3), *Forensic Entomology: the Utility of Arthropods in Legal Investigations*, Byrd, J. H. & Castner, J. L. (eds.), [CRC Press](/source/CRC_Press), pp. [3–4](https://archive.org/details/forensicentomolo0000unse/page/3), ISBN 978-0-8493-8120-1

1. Dossey, Aaron (December 2010). "Insects and their chemical weaponry: New potential for drug discovery". *Natural Product Reports*. **27** (12): 1737–1757. [doi:10.1039/C005319H](https://doi.org/10.1039/C005319H). [PMID 20957283](https://pubmed.ncbi.nlm.nih.gov/20957283)

1. Spagna, J. C.; Goldman D. I.; Lin P.-C.; Koditschek D. E.; R. J. Full (March 2007). ["Distributed mechanical feedback in arthropods and robots simplifies control of rapid running on challenging terrain"](http://polypedal.berkeley.edu/twiki/pub/PolyPEDAL/PolypedalPublications/Distributed_BB.pdf). *[Bioinspiration & Biomimetics](/source/Bioinspiration_%26_Biomimetics)*. **2** (1): 9–18. [Bibcode:2007BiBi....2....9S](https://ui.adsabs.harvard.edu/abs/2007BiBi....2....9S). [doi:10.1088/1748-3182/2/1/002](https://doi.org/10.1088/1748-3182/2/1/002). [PMID 17671322](https://pubmed.ncbi.nlm.nih.gov/17671322). [S2CID 21564918](https://api.semanticscholar.org/CorpusID:21564918). [Archived](https://web.archive.org/web/20120310042430/http://polypedal.berkeley.edu/twiki/pub/PolyPEDAL/PolypedalPublications/Distributed_BB.pdf) 2012-03-10 at the Wayback Machine.

1. Kazuo Tsuchiya; Shinya Aoi; & Katsuyoshi Tsujita (2006), "A Turning Strategy of a Multi-legged Locomotion Robot", *Adaptive Motion of Animals and Machines*, pp. 227–236, [CiteSeerX 10.1.1.573.1846](https://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.573.1846). [doi:10.1007/4-431-31381-8_20](https://doi.org/10.1007/4-431-31381-8_20). ISBN 978-4-431-24164-5

1. Hill, D. (1997), *The Economic Importance of Insects*, Springer, pp. 77–92, ISBN 978-0-412-49800-8

1. Goodman, Jesse L.; Dennis, David Tappen; Sonenshine, Daniel E. (2005), [*Tick-borne diseases of humans*](https://books.google.com/books?id=dKlUARLKT9IC), [ASM Press](/source/ASM_Press), p. 114, ISBN 978-1-55581-238-6, retrieved 2010-03-29

1. Potter, M. F., ["Parasitic Mites of Humans"](http://www.ca.uky.edu/entomology/entfacts/ef637.asp), University of Kentucky College of Agriculture, [archived](https://web.archive.org/web/20090108202742/http://www.ca.uky.edu/entomology/entfacts/ef637.asp) 2009-01-08 at the Wayback Machine, retrieved 2008-10-25

1. Klenerman, Paul & Lipworth, Brian, ["House dust mite allergy"](http://www.netdoctor.co.uk/health_advice/facts/allergyhousedustmite.htm), *Netdoctor*, [archived](https://web.archive.org/web/20080211110450/http://www.netdoctor.co.uk/health_advice/facts/allergyhousedustmite.htm) 11 February 2008 at the Wayback Machine, retrieved 2008-02-20

1. Kogan, M.; Croft, B. A.; Sutherst, R. F. (1999), ["Applications of ecology for integrated pest management"](https://books.google.com/books?id=aw5Iycas70cC&pg=PA681), *Ecological Entomology*, John Wiley & Sons, pp. 681–736, ISBN 978-0-471-24483-7

1. Gorham, J. Richard (1991), ["Insect and Mite Pests in Food: An Illustrated Key"](http://www.afpmb.org/pubs/tims/tg27/docs/Insect%20and%20Mite%20Pests%20in%20Food%20Gorham.pdf), *Agriculture Handbook Number 655*, [United States Department of Agriculture](/source/United_States_Department_of_Agriculture), pp. 1–767, [archived](https://web.archive.org/web/20071025222603/http://www.afpmb.org/pubs/tims/tg27/docs/Insect%20and%20Mite%20Pests%20in%20Food%20Gorham.pdf) October 25, 2007 at the Wayback Machine, retrieved 2010-05-06

1. Jong, D. D.; Morse, R. A.; & Eickwort, G. C. (January 1982). "Mite Pests of Honey Bees". *[Annual Review of Entomology](/source/Annual_Review_of_Entomology)*. **27**: 229–252. [doi:10.1146/annurev.en.27.010182.001305](https://doi.org/10.1146/annurev.en.27.010182.001305)

1. Metcalf, Robert Lee & Luckmann, William Henry (1994), [*Introduction to insect pest management*](https://books.google.com/books?id=pW1dXL2EgnMC), Wiley-IEEE, p. 4, ISBN 978-0-471-58957-0

1. Shultz, J. W. (2001), "Chelicerata (Arachnids, Including Spiders, Mites and Scorpions)", *Encyclopedia of Life Sciences*, John Wiley & Sons, Ltd., [doi:10.1038/npg.els.0001605](https://doi.org/10.1038/npg.els.0001605). ISBN 978-0-470-01617-6

1. Osakabe, M. (March 2002), "Which predatory mite can control both a dominant mite pest, *Tetranychus urticae*, and a latent mite pest, *Eotetranychus asiaticus*, on strawberry?", *[Experimental and Applied Acarology](/source/Experimental_and_Applied_Acarology)*. **26** (3–4): 219–230, [doi:10.1023/A:1021116121604](https://doi.org/10.1023/A:1021116121604). [PMID 12542009](https://pubmed.ncbi.nlm.nih.gov/12542009). [S2CID 10823576](https://api.semanticscholar.org/CorpusID:10823576)

1. ["What is a bug? Insects, arachnids, and myriapods"](https://www.tepapa.govt.nz/discover-collections/read-watch-play/science/your-bug-questions-answered/what-bug-insects-arachnids) at the Museum of New Zealand Te Papa Tongarewa website. Accessed 10 March 2022.

1. Gilbert Waldbauer. *The Handy Bug Answer Book.* Visible Ink, 1998. [pp. 5–26.](https://archive.org/details/handybuganswerbo00wald/page/5/mode/2up) ISBN 978-1-57859-049-0

1. Snodgrass, R. E. (1960), "Facts and theories concerning the insect head", *Smithsonian Miscellaneous Collections*. **142**: 1–61

1. Dunlop, J. A. (1999). "A replacement name for the trigonotarbid arachnid *Eotarbus* Dunlop". *[Palaeontology](/source/Palaeontology_(journal))*. **42** (1): 191. [Bibcode:1999Palgy..42..191D](https://ui.adsabs.harvard.edu/abs/1999Palgy..42..191D). [doi:10.1111/1475-4983.00068](https://doi.org/10.1111/1475-4983.00068). [S2CID 83825904](https://api.semanticscholar.org/CorpusID:83825904)

1. Codex commission for food hygiene (1985), ["Codex Standard 152 of 1985 (on "Wheat Flour")"](http://www.codexalimentarius.net/download/standards/50/CXS_152e.pdf), *Codex Alimentarius*, [Food and Agriculture Organization](/source/Food_and_Agriculture_Organization), [archived](https://web.archive.org/web/20101231033646/http://www.codexalimentarius.net/download/standards/50/CXS_152e.pdf) 2010-12-31 at the Wayback Machine, retrieved 2010-05-08.

1. ["Complete list of Official Standards"](http://www.codexalimentarius.net/web/standard_list.do?lang=en), *Codex Alimentarius*, Food and Agriculture Organization, [archived](https://web.archive.org/web/20100131140203/http://www.codexalimentarius.net/web/standard_list.do?lang=en) 2010-01-31 at the Wayback Machine, retrieved 2010-05-08

1. ["The Food Defect Action Levels"](http://www.cfsan.fda.gov/~dms/dalbook.html), [U. S. Food and Drug Administration](/source/Food_and_Drug_Administration), [archived](https://web.archive.org/web/20061218113700/http://www.cfsan.fda.gov/~dms/dalbook.html) 18 December 2006 at the Wayback Machine, retrieved 2006-12-16

### Bibliography

- Gould, S. J. (1990). *Wonderful Life: The Burgess Shale and the Nature of History*. Hutchinson Radius. [Bibcode:1989wlbs.book.....G](https://ui.adsabs.harvard.edu/abs/1989wlbs.book.....G). ISBN 978-0-09-174271-3.
- Ruppert, E. E.; R. S. Fox; R. D. Barnes (2004). [*Invertebrate Zoology*](https://archive.org/details/isbn_9780030259821). 7th ed. [Brooks/Cole](/source/Brooks/Cole). ISBN 978-0-03-025982-1.

## External links

- [Venomous Arthropods](http://entomology.ifas.ufl.edu/fasulo/vector/chapter_07.htm) [Archived](https://web.archive.org/web/20100131053456/http://entomology.ifas.ufl.edu/fasulo/vector/chapter_07.htm) 31 January 2010 at the Wayback Machine chapter in [United States Environmental Protection Agency](/source/United_States_Environmental_Protection_Agency) and [University of Florida](/source/University_of_Florida)/[Institute of Food and Agricultural Sciences](/source/Institute_of_Food_and_Agricultural_Sciences) National Public Health Pesticide Applicator Training Manual
- [Arthropods – Arthropoda](https://web.archive.org/web/20170821005914/http://www.insectlifeforms.com/Phylums488/JOINTED_LEGGED_ANIMALS_ARTHROPODA_6050_488.aspx) Insect Life Forms

---
Adapted from the Wikipedia article [Arthropod](https://en.wikipedia.org/wiki/Arthropod) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Arthropod?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.