{{Short description|Subphylum of arthropods}} {{Automatic taxobox | name = Myriapods | fossil_range = {{fossilrange|Wenlock|Present|earliest=500|latest=0}} | image = Myriapod collage.png | image_caption = Representatives of the four extant myriapod classes. Clockwise from top left: Chilopoda, Diplopoda, Symphyla, and Pauropoda | taxon = Myriapoda | authority = Latreille, 1802 | subdivision_ranks = Classes | subdivision_ref = <ref>{{ITIS |taxon=Myriapoda |id=563885}}</ref> | subdivision = *Chilopoda *Diplopoda *Pauropoda *Symphyla }}
'''Myriapods''' ({{etymology|grc|''{{wikt-lang|grc|μυρίος}}'' ({{grc-transl|μυρίος}})|countless||''{{wikt-lang|grc|πούς}}'' ({{grc-transl|πούς}})|foot}}) are the members of subphylum '''Myriapoda''', containing arthropods such as millipedes and centipedes. The group contains about 13,000 species, all of them terrestrial.<ref name="Berkeley">{{cite web |url=http://www.ucmp.berkeley.edu/arthropoda/uniramia/myriapoda.html |title=Introduction to the Myriapoda |publisher=University of California, Berkeley |author=Ben Waggoner |date=February 21, 1996|access-date=November 9, 2021}}</ref>
Although molecular evidence and similar fossils suggests a diversification in the Cambrian Period,<ref>{{cite journal |author1=Markus Friedrich |author2=Diethard Tautz |name-list-style=amp |year=2002 |journal=Nature |volume=376 |issue=6536 |pages=165–167 |doi=10.1038/376165a0 |title=Ribosomal DNA phylogeny of the major extant arthropod classes and the evolution of myriapods |pmid=7603566 |bibcode=1995Natur.376..165F|s2cid=4270910 }}</ref><ref name="Berkeley"/> the oldest known fossil record of myriapods dates between the Late Silurian and Early Devonian,<ref>{{cite journal|first1=C.H.|last1=Wellman|first2=G.|last2=Lopes|first3=Z.|last3=McKellar|first4=A.|last4=Hartley|year=2023|title=Age of the basal 'Lower Old Red Sandstone' Stonehaven Group of Scotland: The oldest reported air-breathing land animal is Silurian (late Wenlock) in age|journal=Journal of the Geological Society|volume=181 |article-number=jgs2023-138 |publisher=The Geological Society of London|doi=10.1144/jgs2023-138|issn=0016-7649|doi-access=free|hdl=2164/22754|hdl-access=free}}</ref><ref>{{Cite journal |last1=Brookfield |first1=M. E. |last2=Catlos |first2=E. J. |last3=Garza |first3=H. |date=2024-07-07 |title=The oldest 'millipede'-plant association? Age, paleoenvironments and sources of the Silurian lake sediments at Kerrera, Argyll and Bute, Scotland |url=https://www.tandfonline.com/doi/full/10.1080/08912963.2024.2367554 |journal=Historical Biology |volume=37 |issue=5 |language=en |pages=1158–1170 |doi=10.1080/08912963.2024.2367554 |issn=0891-2963|url-access=subscription }}</ref> with ''Pneumodesmus'' preserving the earliest known evidence of air-breathing on land.<ref name="myriapoda">{{cite web |url=http://www.myriapoda.org/diplopoda/millipede_fossils.html |title=Millipede Fossils |publisher=East Carolina University |date=March 1, 2005 |author1=Rowland Shelley |author2=Paul Marek |name-list-style=amp |url-status=usurped |archive-url=https://web.archive.org/web/20110527071726/http://www.myriapoda.org/diplopoda/millipede_fossils.html |archive-date=May 27, 2011 }}</ref><ref name="Garwood">{{cite journal |last1=Garwood |first1=Russell J. |last2=Edgecombe |first2=Gregory D. |date=September 2011 |title=Early Terrestrial Animals, Evolution, and Uncertainty |journal=Evolution: Education and Outreach |volume=4 |issue=3 |pages=489–501 |doi=10.1007/s12052-011-0357-y |doi-access=free }}</ref> Other early myriapod fossil species around the similar time period include ''Kampecaris obanensis'' and ''Archidesmus'' sp.<ref name=":4">{{Cite journal |last1=Brookfield |first1=M. E. |last2=Catlos |first2=E. J. |last3=Suarez |first3=S. E. |date=2021-10-03 |title=Myriapod divergence times differ between molecular clock and fossil evidence: U/Pb zircon ages of the earliest fossil millipede-bearing sediments and their significance |url=https://www.tandfonline.com/doi/full/10.1080/08912963.2020.1762593 |journal=Historical Biology |language=en |volume=33 |issue=10 |pages=2014–2018 |doi=10.1080/08912963.2020.1762593 |bibcode=2021HBio...33.2014B |s2cid=238220137 |issn=0891-2963|url-access=subscription }}</ref> The phylogenetic classification of myriapods is still debated.
The scientific study of myriapods is myriapodology, and those who study myriapods are myriapodologists.<ref>{{cite book |author=Sue Hubbell |year=2000 |title=Waiting for Aphrodite: Journeys Into the Time Before Bones |publisher=Houghton Mifflin Harcourt |isbn=978-0-618-05684-2 |url=https://books.google.com/books?id=esw4_ksiTkEC&pg=PA53 |page=53}}</ref>
==Anatomy== [[File:HouseCentipedeCloseup.jpg|left|thumb|The head of ''Scutigera coleoptrata'', showing antennae, compound eyes and mouthparts]] Myriapods have a single pair of antennae and, in most cases, simple eyes. Exceptions are the two classes of symphylans and pauropods, the millipede order Polydesmida and the centipede order Geophilomorpha, which are all eyeless.<ref>{{cite book|title=Deep Metazoan Phylogeny: The Backbone of the Tree of Life. New insights from analyses of molecules, morphology, and theory of data analysis|page=308|isbn=978-3-11-027746-3|year=2014|editor-last1=Wägele|editor-first1=J. Wolfgang|editor-last2=Bartolomaeus|editor-first2=Thomas|last1=Wägele|first1=J. Wolfgang|last2=Kück|first2=Patrick|chapter=Arthropod phylogeny and the origin of Tracheata (=Atelocerata) from Remipedia-like ancestors|chapter-url=https://books.google.com/books?id=T67pBQAAQBAJ&dq=Symphyla+Pauropoda+eyes&pg=PA308|access-date=20 January 2025|via=Google Books|publisher=Walter de Gruyter GmbH}}</ref> The house centipedes (Scutigera) on the other hand, have large and well-developed compound eyes.<ref name="Müller 2003">{{cite journal |last1=Müller |first1=C.H.G. |last2=Rosenberg |first2=J. |last3=Richter |first3=S. |last4=Meyer-Rochow |first4=V.B. |title=The compound eye of ''Scutigera coleoptrata'' (Linnaeus, 1758) (Chilopoda; Notostigmophora): an ultrastructural re-investigation that adds support to the Mandibulata concept |journal=Zoomorphology |date=2003 |volume=122 |issue=4 |pages=191–209 |doi=10.1007/s00435-003-0085-0|s2cid=6466405 }}</ref> The mouthparts lie on the underside of the head, with an "epistome" and labrum forming the upper lip, and a pair of maxillae forming the lower lip. A pair of mandibles lie inside the mouth. Myriapods breathe through spiracles that connect to a tracheal system similar to that of insects. There is a long tubular heart that extends through much of the body, but usually few, if any, blood vessels.<ref name=IZ>{{cite book |first=Robert D. |last=Barnes |year=1982 |title= Invertebrate Zoology |publisher=Holt-Saunders International |location=Philadelphia, PA |pages=810–827 |isbn=978-0-03-056747-6}}</ref>
Malpighian tubules excrete nitrogenous waste into the digestive system, which typically consists of a simple tube. Although the ventral nerve cord has a ganglion in each segment, the brain is relatively poorly developed.<ref name=IZ/>
During mating, male myriapods produce a packet of sperm, or spermatophore, which they must transfer to the female externally; this process is often complex and highly developed. The female lays eggs which hatch as much-shortened versions of the adults, with only a few segments and as few as three pairs of legs. With the exception of the two centipede orders Scolopendromorpha and Geophilomorpha, which have epimorphic development (all body segments are formed segments embryonically), the young add additional segments and limbs as they repeatedly moult to reach the adult form.<ref name=IZ/>
The number of segments can range from 15 to 173.<ref name="Palm">{{cite book |last1=Palm |first1=Per-Olof |title=Plus 7 - Biologi, zoologi, Botanik |date=1964 |publisher=FIB PRISMA TIDEN |location=Stockholm |page=219 |edition=1}}</ref> The process of adding new segments during postembryonic growth is known as anamorphosis, of which there are three types: euanamorphosis, emianamorphosis, and teloanamorphosis. In euanamorphosis, every moult is followed by addition of new segments, even after reaching sexual maturity; in emianamorphosis, new segments are added until a certain stage, and further moults happen without addition of segments; and in teloanamorphosis, where the addition of new segments stops after the adult form is reached, after no further moults occur.<ref>{{cite journal |first1=Henrik |last1=Enghoff |first2=Wolfgang |last2=Dohle |first3=J. Gordon |last3=Blower |date=October 1993 |title=Anamorphosis in millipedes (''Diplopoda'') – the present state of knowledge with some developmental and phylogenetic considerations |journal=Zoological Journal of the Linnean Society |volume=109 |issue=2 |pages=103–234 |type=abstract |doi=10.1111/j.1096-3642.1993.tb00305.x |url=https://academic.oup.com/zoolinnean/article-abstract/109/2/103/2646268?redirectedFrom=fulltext|url-access=subscription }}</ref>
==Ecology== {{Myriapoda sidebar}} Myriapods are most abundant in moist forests, where they fulfill an important role in breaking down decaying plant material,<ref name="Berkeley" /> although a few live in grasslands, semi-arid habitats or even deserts.<ref>{{cite web |url=https://www.britannica.com/ebc/article-9054558 |title=Myriapod |publisher=Britannica Concise Encyclopedia}}</ref> A very small percentage of species are littoral (found along the sea shore).<ref name="Barber2009">{{cite journal|author=Barber, A.D.|title=Littoral myriapods: a review|url=http://www.senckenberg.de/files/content/forschung/publikationen/soilorganisms/volume_81_3/33_barber.pdf|journal=Soil Organisms|volume=81|issue=3|pages=735–760|year=2009|access-date=2013-11-05|archive-url=https://web.archive.org/web/20160303234850/http://www.senckenberg.de/files/content/forschung/publikationen/soilorganisms/volume_81_3/33_barber.pdf|archive-date=2016-03-03}}</ref><ref name="Littoral Myriapods">{{cite web|editor-last=Barber|editor-first=A.D. |title=World Database of Littoral Myriapoda|url=http://www.marinespecies.org/myriapoda|work=World Register of Marine Species|access-date=25 October 2013|year=2013}}</ref> The majority are detritivorous, with the exception of centipedes, which are chiefly nocturnal predators.
A few species of centipedes and millipedes are able to produce light and are therefore bioluminescent.<ref name="Rosenberg & Meyer-Rochow 2009">{{cite book|last1=Rosenberg|first1=Joerg|last2=Meyer-Rochow|first2=Victor Benno|title=Bioluminescence in Focus - a collection of illuminating essays|year=2009|editor=Meyer-Rochow V.B.|publisher=Research Signpost; Trivandrum, Kerala, India|pages=139–147}}</ref> Pauropodans and symphylans are small, sometimes microscopic animals that resemble centipedes superficially and live in soils. Millipedes differ from the other groups in having their body segments fused into pairs, giving the appearance that each segment bears two pairs of legs, while the other three groups have a single pair of legs on each body segment.
Although not generally considered dangerous to humans, many millipedes produce noxious secretions (often containing benzoquinones) which in rare cases can cause temporary blistering and discolouration of the skin.<ref>{{cite web |title=Strange and Unusual Millipedes |url=http://www.herper.com/myriapods/strange.html |publisher=herper.com |access-date=July 2, 2007 |archive-url=https://web.archive.org/web/20120402192616/http://www.herper.com/myriapods/strange.html |archive-date=April 2, 2012 }}</ref> Large centipedes can bite humans, and although the bite may cause intense pain and discomfort, fatalities are extremely rare.<ref>{{cite journal |author1=Sean P. Bush |author2=Bradley O. King |author3=Robert L. Norris |author4=Scott A. Stockwell |title=Centipede envenomation |journal=Wilderness & Environmental Medicine |volume=12 |issue=2 |pages=93–99 |year=2001 |pmid=11434497 |url=http://www.wemjournal.org/article/S1080-6032%2801%2970700-4/abstract |doi=10.1580/1080-6032(2001)012[0093:CE]2.0.CO;2|doi-access=free |url-access=subscription }}</ref>
==Classification== There has been much debate as to which arthropod group is most closely related to the Myriapoda.<ref>{{cite journal |author=Gregory D. Edgecombe |year=2004 |title=Morphological data, extant Myriapoda, and the myriapod stem-group |journal=Contributions to Zoology |volume=73 |issue=3 |pages=207–252 |doi=10.1163/18759866-07303002 |doi-access=free }}</ref> Under the Mandibulata hypothesis, Myriapoda is the sister taxon to Pancrustacea, a group comprising the Crustacea and Hexapoda (insects and their close relatives). Under the Atelocerata hypothesis, Hexapoda is the closest, whereas under the Paradoxopoda hypothesis, Chelicerata is the closest. This last hypothesis, although supported by few, if any, morphological characters, is supported by a number of molecular studies.<ref>{{cite journal |title=Phylogeny of Arthropoda inferred from mitochondrial sequences: strategies for limiting the misleading effects of multiple changes in pattern and rates of substitution |author=Alexandre Hassanin |journal=Molecular Phylogenetics and Evolution |volume=38 |year=2006 |pages=100–116 |doi=10.1016/j.ympev.2005.09.012 |pmid=16290034 |issue=1|bibcode=2006MolPE..38..100H }}</ref> A 2020 study found numerous characters of the eye and preoral region suggesting that the closest relatives to crown myriapods are the extinct Euthycarcinoids.<ref>{{Cite journal|last1=Edgecombe|first1=Gregory D.|last2=Strullu-Derrien|first2=Christine|last3=Góral|first3=Tomasz|last4=Hetherington|first4=Alexander J.|last5=Thompson|first5=Christine|last6=Koch|first6=Markus|date=2020-04-01|title=Aquatic stem group myriapods close a gap between molecular divergence dates and the terrestrial fossil record|journal=Proceedings of the National Academy of Sciences|volume=117|issue=16|pages=8966–8972|language=en|doi=10.1073/pnas.1920733117|issn=0027-8424|pmid=32253305|pmc=7183169|bibcode=2020PNAS..117.8966E |doi-access=free}}</ref> There are four classes of extant myriapods, Chilopoda (centipedes), Diplopoda, Pauropoda and Symphyla, containing a total of around 12,000 species.<ref name="Chapman">{{cite book |author=A. D. Chapman |title=Numbers of Living Species in Australia and the World |publisher=Department of the Environment and Heritage |year=2005 |isbn=978-0-642-56850-2 |page=23 |url=http://www.environment.gov.au/biodiversity/abrs/publications/other/species-numbers/pubs/number-living-species-report.pdf |archive-url=https://web.archive.org/web/20071025220345/http://www.environment.gov.au/biodiversity/abrs/publications/other/species-numbers/pubs/number-living-species-report.pdf |archive-date=25 October 2007 |access-date=1 January 2011}}</ref> While each of these groups of myriapods is believed to be monophyletic, relationships among them are less certain.<ref>{{cite journal |author=Jerome C. Regier, Heather M. Wilson & Jeffrey W. Shultz |year=2005 |title=Phylogenetic analysis of Myriapoda using three nuclear protein-coding genes |journal=Molecular Phylogenetics and Evolution |volume=34 |issue=1 |pages=147–158 |doi=10.1016/j.ympev.2004.09.005 |pmid=15579388|bibcode=2005MolPE..34..147R }}</ref>
===Centipedes=== {{Main|Centipede}} [[File:Scolopendra fg01.JPG|thumb|''Scolopendra cingulata'', a centipede]] Centipedes make up the class Chilopoda. They are fast, predatory and venomous, hunting mostly at night. During the day, they generally lie under rocks, during the night they chase larvae, earthworms and even lizards and small rodents.<ref name="Palm">{{cite book |last1=Palm |first1=Per-Olof |title=Plus 7 - Biologi, zoologi, Botanik |date=1964 |publisher=FIB PRISMA TIDEN |location=Stockholm |page=219 |edition=1}}</ref> There are around 3,300 species,<ref name="Chapman" /> ranging from the diminutive ''Nannarrup hoffmani'' (less than 12 mm or {{frac|2}} in in length)<ref>{{Cite web |date=2008-04-30 |title=City Centipede: An Urban Legend with Real Legs - TIME |url=http://www.time.com/time/magazine/article/0,9171,1002980,00.html?promoid=googlep |archive-url=https://web.archive.org/web/20080430015418/http://www.time.com/time/magazine/article/0,9171,1002980,00.html?promoid=googlep |archive-date=2008-04-30 |access-date=2022-10-30 }}</ref> to the giant ''Scolopendra gigantea'', which may exceed {{convert|30|cm|in|0}}.
===Millipedes=== {{Main|Millipede}} [[File:Tachypodoiulus niger 1.jpg|thumb|''Tachypodoiulus niger'', a millipede]] Millipedes form the class Diplopoda. Most millipedes are slower than centipedes, and feed on leaf litter and detritus. Except for the first segment called collum, which don't have any appendages, and the next three segments with a single pair of legs each, they are distinguished by the fusion of each pair of body segments into a single unit, giving the appearance of having two pairs of legs per segment. It is also common for the sternites, pleurites and tergites to fuse into rigid armour rings.<ref>{{cite journal | pmc=1402290 | year=2006 | last1=Janssen | first1=R. | last2=Prpic | first2=N. M. | last3=Damen | first3=W. G. | title=A review of the correlation of tergites, sternites, and leg pairs in diplopods | journal=Frontiers in Zoology | volume=3 | article-number=2 | doi=10.1186/1742-9994-3-2 | pmid=16451739 | doi-access=free }}</ref> The males produce aflagellate sperm cells, unlike the rest of the myriapods which produce flagellated sperm.<ref>{{Cite book |last1=Schierwater |first1=Bernd |url=https://books.google.com/books?id=Bk4vEAAAQBAJ&dq=%2522aflagellate+in+Diplopoda%2522&pg=PA447 |title=Invertebrate Zoology: A Tree of Life Approach |last2=DeSalle |first2=Rob |date=2021-07-08 |publisher=CRC Press |isbn=978-1-4822-3582-1 |language=en}}</ref> Around 12,000 species have been described, which may represent less than a tenth of the true global millipede diversity.<ref name="Chapman"/> Although the name "millipede" is a compound word formed from the Latin roots ''millia'' ("thousand") and ''pes'' (gen. ''pedis'') ("foot"), millipedes typically have between 36 and 400 legs. In 2021, however, was described ''Eumillipes persephone,'' the first species known to have 1,000 or more legs, possessing 1,306 of them.<ref>{{Cite journal|last1=Marek|first1=Paul E.|last2=Buzatto|first2=Bruno A.|last3=Shear|first3=William A.|last4=Means|first4=Jackson C.|last5=Black|first5=Dennis G.|last6=Harvey|first6=Mark S.|last7=Rodriguez|first7=Juanita|date=December 2021|title=The first true millipede—1306 legs long|journal=Scientific Reports|language=en|volume=11|issue=1|page=23126|doi=10.1038/s41598-021-02447-0|pmid=34916527|pmc=8677783|bibcode=2021NatSR..1123126M |s2cid=245317751|issn=2045-2322}}</ref> Pill millipedes are much shorter, and are capable of rolling up into a ball, like pillbugs.
===Symphyla=== {{Main|Symphyla}} [[File:Scutigerella 42508806.jpg|thumb|A species of ''Scutigerella,'' a genus of symphylan]] Symphylans, or garden centipedes, are closely related to centipedes and millipedes.<ref name=":1">{{Cite web |last1=Gesell |first1=Stanley |last2=Calvin |first2=Dennis |date=2017-03-09 |title=Garden Symphylan as a Pest of Field Crops |url=https://extension.psu.edu/garden-symphylan-as-a-pest-of-field-crops}}</ref><ref name=":2">{{Cite web |last=University |first=Utah State |title=Sympylans (Garden Centipede) |url=https://extension.usu.edu/vegetableguide/leafy-greens/garden-centipede |access-date=2022-10-30 |website=extension.usu.edu |language=en}}</ref> They are 3 to 6 cm long, and have 6 to 12 pairs of legs, depending on their life stage.<ref name=":1" /><ref name=":2" /><ref name=":3">{{Cite web |date=2007-08-03 |title=Symphylan Identification |url=http://mint.ippc.orst.edu/symphid.htm |archive-url=https://web.archive.org/web/20070803172418/http://mint.ippc.orst.edu/symphid.htm |archive-date=2007-08-03 |access-date=2022-10-30 }}</ref> Their eggs, which are white and spherical and covered with small hexagonal ridges, are laid in batches of 4 to 25 at a time, and usually take up to 40 days to hatch.<ref name=":1" /><ref name=":2" /><ref name=":3" /> There are about 200 species worldwide.<ref>{{Cite web |date=2009-09-26 |title=Numbers of Living Species in Australia and the World |url=http://www.environment.gov.au/biodiversity/abrs/publications/other/species-numbers/pubs/number-living-species-report.pdf |archive-url=https://web.archive.org/web/20090926194206/http://www.environment.gov.au/biodiversity/abrs/publications/other/species-numbers/pubs/number-living-species-report.pdf |archive-date=2009-09-26 |access-date=2022-10-30 }}</ref>
===Pauropoda=== {{Main|Pauropoda}} [[File:Eurypauropodid (12742282145) crop.jpg|thumb|A species of Samarangopus, a genus of pauropod]] Pauropoda is another small group of small myriapods. They are typically 0.5–2.0 mm long and live in the soil on all continents except Antarctica.{{citation needed|date=August 2022}} Over 700 species have been described.<ref name="Chapman"/> They are believed to be the sister group to millipedes, and have the dorsal tergites fused across pairs of segments, similar to the more complete fusion of segments seen in millipedes.<ref>{{cite web |url=http://www.kendall-bioresearch.co.uk/myriapod.htm |title=Pauropods & Symphylids |author=David Kendall |date=June 6, 2005 |publisher=Kendall Bioresearch}}</ref>
===Arthropleuridea=== {{Main|Arthropleuridea}} [[File:ArthropleuraSide.jpg|thumb|''Arthropleura'', an arthropleuridean]] Arthropleurideans were ancient myriapods that are now extinct, known from the late Silurian to the Permian. The most famous members are from the genus ''Arthropleura'', which was a giant, probably herbivorous, animal that could be up to {{convert|2.63|m|0}} long,<ref name=":0">{{cite journal |last1=Neil Davies |display-authors=etal |date=Dec 21, 2021 |title=The largest arthropod in Earth history: insights from newly discovered Arthropleura remains (Serpukhovian Stainmore Formation, Northumberland, England) |url=https://jgs.lyellcollection.org/content/early/2021/11/19/jgs2021-115 |journal=Journal of the Geological Society |volume=179 |issue=3 |article-number=jgs2021-115 |doi=10.1144/jgs2021-115 |s2cid=245401499}}</ref> but the group also includes species less than {{convert|1|cm|in|abbr=on}}. Arthropleuridea was historically considered a distinct class of myriapods, but since 2000 scientific consensus has viewed the group as a subset of millipedes, although the relationship of arthropleurideans to other millipedes and to each other is debated.<ref name=Wilson&Shear2000>{{cite journal|last1=Wilson|first1=Heather M.|last2=Shear|first2=William A.|title=Microdecemplicida, a new order of minute arthropleurideans (Arthropoda: Myriapoda) from the Devonian of New York State, U.S.A.|journal=Transactions of the Royal Society of Edinburgh: Earth Sciences|date=2000|volume=90|issue=4|pages=351–375|doi=10.1017/S0263593300002674|s2cid=129597005 }}</ref><ref>{{cite journal|last1=Shear|first1=William A.|last2=Edgecombe|first2=Gregory D.|title=The geological record and phylogeny of the Myriapoda|journal=Arthropod Structure & Development|date=2010|volume=39|issue=2–3|pages=174–190|doi=10.1016/j.asd.2009.11.002|pmid=19944188|bibcode=2010ArtSD..39..174S }}</ref>
===Myriapod relationships === thumb|right|upright=1.0|Some of the various hypotheses of myriapod phylogeny. Morphological studies (trees a and b) support a sister grouping of Diplopoda and Pauropoda, while studies of DNA or amino acid similarities suggest a variety of different relationships, including the relationship of Pauropoda and Symphyla in tree c
A variety of groupings (clades) of the myriapod classes have been proposed, some of which are mutually exclusive, and all of which represent hypotheses of evolutionary relationships. Traditional relationships supported by morphological similarities (anatomical or developmental similarities) are challenged by newer relationships supported by molecular evidence (including DNA sequence and amino acid similarities).<ref name=Edgecombe&Giribet2002>{{cite book|author1= Edgecombe GD |author2=Giribet G |year= 2002|chapter= Myriapod phylogeny and the relationships of Chilopoda|title= Biodiversidad, Taxonomia y Biogeografia de Artropodos de Mexico: Hacia una S´ıntesis de su Conocimiento|editor1= J Llorente Bousquets |editor2=JJ Morrone |editor3=HP Ulloa|pages=143–168 |publisher= Univ. Nac. Aut´on Mexico: Prensas Ciencias |chapter-url=http://www.nhm.ac.uk/resources-rx/files/edgecombe--giribet-2002-morrone-94087.pdf}}</ref><ref name="Miyazawa et al 2014">{{cite journal |last1=Miyazawa |first1=Hideyuki |last2=Ueda |first2=Chiaki |last3=Yahata |first3=Kensuke |last4=Su |first4=Zhi-Hui |title=Molecular phylogeny of Myriapoda provides insights into evolutionary patterns of the mode in post-embryonic development|journal=Scientific Reports |date=2014 |volume=4 |issue=4127 |page=4127 |doi=10.1038/srep04127 |pmid=24535281 |pmc=3927213 |bibcode=2014NatSR...4.4127M}}</ref>
*'''Dignatha''' (also called Collifera) is a clade consisting of millipedes and pauropods, and is supported by morphological similarities including the presence of a gnathochilarium (a modified jaw and plate apparatus) and a collum, a legless segment behind the head. *'''Trignatha''' (also called Atelopoda) is a grouping of centipedes and symphylans, united by similarities of mouthparts. *'''Edafopoda''' is a grouping of symphylans and pauropodans that is supported by shared genetic sequences, yet conflicts with Dignatha and Trignatha.<ref name="Zwick et al 2012">{{cite journal |last1=Zwick|first1=Andreas |last2=Regier |first2=Jerome C. |last3=Zwickl|first3=Derrick J. |last4=Gadagkar|first4=Sudhindra R.|title=Resolving Discrepancy between Nucleotides and Amino Acids in Deep-Level Arthropod Phylogenomics: Differentiating Serine Codons in 21-Amino-Acid Models |journal=PLOS ONE|date=2012 |volume=7|issue=11|article-number=e47450 |doi=10.1371/journal.pone.0047450 |pmid=23185239 |pmc=3502419 |bibcode=2012PLoSO...747450Z|doi-access=free}}</ref> *'''Pectinopoda''' consist of millipedes and centipedes, a classification that also supports Edafopoda.<ref>{{cite journal|last1=Benavides|first1=Ligia R.|last2=Edgecombe|first2=Gregory D.|last3=Giribet|first3=Gonzalo|title=Re-evaluating and dating myriapod diversification with phylotranscriptomics under a regime of dense taxon sampling|journal=Molecular Phylogenetics and Evolution|year=2023|volume=178|article-number=107621 |id=Article No. 107621|doi=10.1016/j.ympev.2022.107621 |pmid=36116731 |bibcode=2023MolPE.17807621B }}</ref><ref>{{cite journal|first1=Mickaël|last1=Lhéritier|last2=Edgecombe|first2=Gregory D.|last3=Garwood|first3=Russell J.|last4=Buisson|first4=Adrien|last5=Gerbe|first5=Alexis|last6=Koch|first6=Nicolás Mongiardino|last7=Vannier|first7=Jean|last8=Escarguel|first8=Gilles|last9=Adrien|first9=Jérome|last10=Fernandez|first10=Vincent|last11=Bergeret-Medina|first11=Aude|last12=Perrier|first12=Vincent|title=Head anatomy and phylogenomics show the Carboniferous giant Arthropleura belonged to a millipede-centipede group|year=2024|volume=10|issue=41|journal=Science Advances|article-number=eadp6362 |doi=10.1126/sciadv.adp6362|pmid=39383233 |doi-access=free|hdl=10141/623138|hdl-access=free|pmc=11463278 |bibcode=2024SciA...10P6362L }}</ref> *'''Progoneata''' is a group encompassing millipedes, pauropods and symphylans while excluding centipedes. Shared features include reproductive openings (gonopores) behind the second body segment, and sensory hairs (trichobothria) with a bulb-like swelling. It is compatible with either Dignatha or Edafopoda.<ref name="Miyazawa et al 2014"/>
== See also == {{Portal|Arthropods}} * Euthycarcinoidea, a group of enigmatic arthropods that may be ancestral to myriapods * Colonization of land, major evolutionary stages leading to terrestrial organisms * Metamerism, the condition of multiple linearly repeated body segments
==References== {{Reflist|32em}}
==External links== {{Wikispecies|Myriapoda}} {{Commons category|Myriapoda}} * [https://web.archive.org/web/20131029184905/http://palaeo.gly.bris.ac.uk/Palaeofiles/Fossilgroups/Myriapoda/fossilrecord.html Myriapod Fossil Record - University of Bristol] * [https://web.archive.org/web/20131021234219/http://www.pensoft.net/journals/ijm/ International Journal of Myriapodology] * [http://www.myriapodology.org/ International Society of Myriapodology] * [http://www.bmig.org.uk/ British Myriapod and Isopod Group] * {{usurped|1=[https://web.archive.org/web/20131023101805/http://nadiplochilo.com/index.html Myriapods, the World's Leggiest Animals - North America]}}
{{Arthropods}} {{Taxonbar|from=Q25823}} {{Authority control}}
Category:Myriapods Category:Animal subphyla Category:Extant Silurian first appearances Category:Taxa named by Pierre André Latreille