# Archaeocaris > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Archaeocaris > Markdown URL: https://mediated.wiki/source/Archaeocaris.md > Source: https://en.wikipedia.org/wiki/Archaeocaris > Source revision: 1307737935 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) {{Short description|Extinct genus of mantis shrimp}} {{Automatic taxobox | fossil_range = [Early Carboniferous](/source/Early_Carboniferous) (early [Tournaisian](/source/Tournaisian) to late [Viséan](/source/Vis%C3%A9an)), {{Fossil range|358.9|330.9}} | image = Archaeocaris vermiformis.jpg | image_caption = Illustration of an ''A. vermiformis'' fossil |parent_authority = Schram, 2008 |display_parents = 2 | taxon = Archaeocaris | authority= Meek, 1872 | type_species = {{extinct}}'''''Archaeocaris vermiformis''''' | type_species_authority = Meek, 1872 | subdivision_ranks = Other species | subdivision = *{{extinct}}'''''A. graffhami'''''
Brooks, 1962 | synonyms = {{collapsible list|bullets=true|title={{small|Synonyms of ''A. vermiformis''}} |''[Crangopsis](/source/Crangopsis) vermiformis'' Ortmann, 1897 }} }} '''''Archaeocaris''''' (meaning "ancient shrimp") is an extinct [genus](/source/genus) of [mantis shrimp](/source/mantis_shrimp) that lived in [North America](/source/North_America) during the [Early Carboniferous](/source/Early_Carboniferous) period. Though it was placed as a member of the family [Perimecturidae](/source/Perimecturidae) until 2008, it is currently deemed the only genus in the family '''Archaeocarididae''', and contains two species. The type species, '''''A. vermiformis''''', was described by [Fielding Bradford Meek](/source/Fielding_Bradford_Meek) in 1872 from specimens collected at the base of the [Waverly Group](/source/Waverly_Group) in [Kentucky](/source/Kentucky). A second species, '''''A. graffhami''''', was named by Harold Kelly Brooks in 1962 based on a fossil found in the [Caney Shale](/source/Caney_Shale) of [Oklahoma](/source/Oklahoma), with additional remains later found in the Pilot Shale of [Nevada](/source/Nevada). Members of this genus were small animals, with ''A. vermiformis'' reaching a length of {{convert|16|-|25|mm|abbr=on|in}} and the largest known ''A. graffhami'' growing {{convert|41|mm|abbr=on|in}} long. A [carapace](/source/carapace) covers the head and part of the [thorax](/source/Thorax_(arthropod_anatomy)), extending further back at the sides than on the top. The [abdomen](/source/abdomen) is made up of six segments and a circular or ovular cross section. The [telson](/source/telson) is ovoid, with broad [uropod](/source/uropod)s at its sides. ''A. vermiformis'' has proportionally larger [mandibles](/source/Mandible_(arthropod_mouthpart)) than ''A. graffhami'', and furrowed abdominal [sclerite](/source/sclerite)s as opposed to the smooth sclerites of the latter species. Like other mantis shrimps, ''Archaeocaris'' was a [carnivore](/source/carnivore) with [raptorial](/source/raptorial) thoracic appendages. These are lined with conical spikes on the penultimate segment and would have been used to grasp prey. ==History of discovery== ''Archaeocaris'' was named in 1872 by American paleontologist [Fielding Bradford Meek](/source/Fielding_Bradford_Meek), with ''A. vermiformis'' as the type and only known species at the time. The [generic name](/source/Generic_name_(biology)) combines the [Greek](/source/Ancient_Greek) words {{lang|grc|ἀρχαῖος}} ({{translit|grc|archaīos}}, meaning "ancient") and {{lang|grc|καρίς}} ({{translit|grc|karís}}, meaning "shrimp"), in reference to its ancient age. Meek studied several specimens of the animal preserved in gray [phosphatic](/source/phosphatic) concretions found at the base of the [Waverly Group](/source/Waverly_Group) near [Danville, Kentucky](/source/Danville%2C_Kentucky), which include the [holotype](/source/holotype) and seven [paratype](/source/paratype)s. These fossils are deposited in the collection of the [US National Museum](/source/US_National_Museum). Meek believed these remains were too imperfectly preserved to determine the animal's classification, though a possible relationship with the modern [Cumacea](/source/Cumacea) is proposed.{{Cite journal |last=Meek |first=F. B. |date=1872 |title=Descriptions of New Western Palæozoic Fossils, Mainly from the Cincinnati Group of the Lower Silurian Series of Ohio |url=https://www.jstor.org/stable/4624198 |journal=Proceedings of the Academy of Natural Sciences of Philadelphia |volume=23 |issue=3 |pages=308–336 |jstor=4624198 |issn=0097-3157}} In 1897, Prussian-born American zoologist [Arnold Edward Ortmann](/source/Arnold_Edward_Ortmann) analysed an additional 27 fossils representing 18 individuals, which he determined to belong to the same species named by Meek. These specimens, kept in the collections of [Princeton University](/source/Princeton_University), were found in [Boyle County, Kentucky](/source/Boyle_County%2C_Kentucky), at or near the same locality where Meek's specimens originate. Ortmann concluded that ''A. vermiformis'' was so similar to known fossils of ''[Crangopsis](/source/Crangopsis)'' that it should not be placed in a separate genus, and thus renamed the species as ''Crangopsis vermiformis'', rendering ''Archaeocaris'' a [junior synonym](/source/junior_synonym) of ''Crangopsis''.{{Cite journal |last=Ortmann |first=A. E. |date=1897-10-01 |title=The systematic position of ''Crangopsis vermiformis'' (Meek) from the sub-Carboniferous rocks of Kentucky |url=https://zenodo.org/records/1756139 |journal=American Journal of Science |volume=4 |issue=22 |pages=283–289 |doi=10.2475/ajs.s4-4.22.283|bibcode=1897AmJS....4..283O }} Further analysis by American paleontologist Harold Kelly Brooks in 1962 found that the aforementioned fossils show clear features of [mantis shrimp](/source/mantis_shrimp)s, and that the species represented by these remains is unrelated to ''Crangopsis'', thus the genus ''Archaeocaris'' was revalidated. In addition to the type species, Brooks described a second species of ''Archaeocaris'' which he named ''A. graffhami'', based on a single specimen collected from the [Caney Shale](/source/Caney_Shale) in [Pontotoc County, Oklahoma](/source/Pontotoc_County%2C_Oklahoma). The [specific name](/source/Specific_name_(zoology)) honors Allen Graffham, who found this specimen.{{Cite journal |last=Brooks |first=Harold Kelly |date=1962 |title=The Paleozoic Eumalacostraca of North America |url=https://www.biodiversitylibrary.org/page/10667554 |journal=Bulletins of American Paleontology |volume=44 |issue=202 |pages=163–338}} While this species was initially known from only one specimen, additional fossils of ''A. graffhami'' would later be found in the upper Pilot Shale on Bactrian Mountain of the [Pahranagat Range](/source/Pahranagat_Range), Nevada, and described in 1979 by American paleontologist [Frederick Schram](/source/Frederick_Schram).{{Cite journal |last1=Schram |first1=F R |date=1979 |title=The Genus ''Archaeocaris'' And A General Review Of The Paleostomatopoda Hoplocarida Malacostraca |url=https://www.biodiversitylibrary.org/page/5784863 |journal=Transactions of the San Diego Society of Natural History |volume=19 |pages=57–65}} Furthermore, Brooks reclassified ''[Perimecturus fraiponti](/source/Perimecturus_fraiponti)'' (described by Belgian paleontologist [Victor van Straelen](/source/Victor_van_Straelen) in 1932) as a species of ''Archaeocaris'' in his 1962 publication. However, this species was reassigned again to ''[Tyrannophontes](/source/Tyrannophontes)'' in 1984 and ''[Gorgonophontes](/source/Gorgonophontes)'' in 2004 (which it is currently placed in), leaving only ''A. vermiformis'' and ''A. graffhami'' as valid species of ''Archaeocaris''.{{Cite journal |last=Schram |first=Frederick R. |date=1984 |title=Upper Pennsylvanian Arthropods from Black Shales of Iowa and Nebraska |url=https://www.jstor.org/stable/1304745 |journal=Journal of Paleontology |volume=58 |issue=1 |pages=197–209 |jstor=1304745 |issn=0022-3360}}{{Cite journal |last=Schöllmann |first=Lothar |date=2004 |title=Archaeostomatopodea (Malacostraca, Hoplocarida) aus dem Namur B (höheres Marsdenium, Karbon) von Hagen-Vorhalle (NRW, Deutschland) und eine Neudefinition einiger Arten der Familie Tyrannophontidae |url=https://www.researchgate.net/publication/287448897 |journal=Geologie und Paläontologie in Westfalen |volume=62 |pages=111–141}} ==Description== A small [crustacean](/source/crustacean), specimens of ''Archaeocaris vermiformis'' range from {{convert|16|-|25|mm|abbr=on|in}} in length (not counting the [rostrum](/source/Rostrum_(anatomy)) or [telson](/source/telson)), with half of the known individuals measuring {{convert|24|-|25|mm|abbr=on|in}} long. ''A. graffhami'' is the larger of the two species, with the biggest specimen measuring about {{convert|41|mm|abbr=on|in}} long. The [cephalothorax](/source/cephalothorax) makes up a third of the body length. The [carapace](/source/carapace) is smooth, covering the head and part of the [thorax](/source/Thorax_(arthropod_anatomy)). It is fused to the frontmost thoracic segments and covers them entirely, while wing-like projections extend from the side of the carapace to the border of the thorax and [abdomen](/source/abdomen). As a result, the carapace covers the sides of the last three thoracic segments while leaving the top of them exposed. The [mandibles](/source/Mandible_(arthropod_mouthpart)) are well [sclerotised](/source/sclerotised), and are proportionally smaller in ''A. graffhami'' than in ''A. vermiformis''; the largest ''A. graffhami'' specimen has mandibles measuring 1.7% the length of its body, while ''A. vermiformis'' has mandibles about 2.3% the body length. The rostrum is triangular and plate-like, with a length equal to its width at the base. The second to fifth pairs of thoracic appendages were [raptorial](/source/raptorial), allowing the animal to grasp prey. Because these appendages are clustered together in the fossils, study of their structure is difficult. They fold into a Z-shape, with the [ischium](/source/Arthropod_leg) pointing forwards while the segment after it points backwards, and the [dactylus](/source/dactylus) (final segment) points forwards again. Conical spikes are present on the propodus (penultimate segment), opposing the sharp dactylus to form a set of grasping claws. The abdomen has an ovular or circular cross section, and is made up of six segments. It makes up most of the animal's length and is around twice as long as the cephalothorax. The bottom margins of the [sclerite](/source/sclerite)s (hardened plates) on each abdominal segment is straight and horizontal, aside from a small upwards curvature at the front. While the abdominal sclerites of ''A. vermiformis'' have marked furrows, those of ''A. graffhami'' are undecorated. The telson is smooth and ovoid in shape, with no indication of it narrowing into a spike like in ''[Perimecturus](/source/Perimecturus)'', though it does become more pointed towards the end. Small protrusions known as caudal furcae are present on the telson of ''A. vermiformis'', giving it a forked appearance. The [uropod](/source/uropod)s can be seen as broad, blade-like lobes. ==Classification== When it was first described, the classification of ''Archaeocaris'' was unclear. Relationships with modern crustaceans were initially proposed, with Meek (1872) and Ortmann (1897) suggesting the genus had affinities with [Cumacea](/source/Cumacea) and [Mysidacea](/source/Mysidacea) respectively. However, both authors overlooked that the animal had features distinctive of mantis shrimps. These were first noticed by Brooks (1962), who recognized ''Archaeocaris'' to be an early mantis shrimp and placed it in the family [Perimecturidae](/source/Perimecturidae), believing it was a close relative of ''[Perimecturus](/source/Perimecturus)''. Brooks assigned this family to the order Palaeostomatopoda (now delisted as a [suborder](/source/suborder) and named [Palaeostomatopodea](/source/Palaeostomatopodea)). As cladistic analyses grew widespread in usage, it became clear that the palaeostomatopods are a [paraphyletic](/source/paraphyletic) grouping, as first discovered by Jenner ''et al.'' (1998).{{Cite journal |last1=Jenner |first1=Ronald A. |last2=Hof |first2=Cees H. J. |last3=Schram |first3=Frederick R. |date=1998 |title=Palaeo- and archaeostomatopods (Hoplocarida, Crustacea) from the Bear Gulch Limestone, Mississippian (Namurian), of central Montana |url=https://www.academia.edu/56829561 |journal=Contributions to Zoology |volume=67 |issue=3 |pages=155 |doi=10.1163/18759866-06703001 |issn=1383-4517|doi-access=free }} This finding was then further confirmed by Schram (2007).{{Cite journal |last=Schram |first=Frederick R. |date=2007 |title=Paleozoic Proto-Mantis Shrimp Revisited |url=https://www.jstor.org/stable/4498847 |journal=Journal of Paleontology |volume=81 |issue=5 |pages=895–916 |doi=10.1666/pleo05-075.1 |jstor=4498847 |bibcode=2007JPal...81..895S |issn=0022-3360|url-access=subscription }} In addition, both studies found that ''Archaeocaris'' is an early-diverging lineage not closely related to ''Perimecturus''. Therefore, the genus was moved to a separate family named Archaeocarididae in 2008. This family is [monotypic](/source/Monotypic_taxon), with ''Archaeocaris'' as its type and only genus, and is placed within Palaeostomatopodea (which is still used in a paraphyletic sense for the convenience of referring to the [evolutionary grade](/source/evolutionary_grade)).{{Cite journal |last=Schram |first=Frederick R. |date=2008 |title=An Adjustment to the Higher Taxonomy of the Fossil Stomatopoda |url=https://www.jstor.org/stable/20111439 |journal=Crustaceana |volume=81 |issue=6 |pages=751–754 |doi=10.1163/156854008784513429 |issn=0011-216X |jstor=20111439|url-access=subscription }} Several studies including Jenner ''et al.'' (1998), Schram (2007), Haug ''et al.'' (2010) and Smith ''et al.'' (2023) have conducted [phylogenetic analyses](/source/phylogenetic_analyses) on fossil mantis shrimps, and have all recovered ''Archaeocaris'' as a [monophyletic](/source/monophyletic) genus and the earliest-diverging lineage within the order [Stomatopoda](/source/Stomatopoda), placing it as a [sister taxon](/source/sister_taxon) to all other members of the order.{{Cite journal |last1=Haug |first1=Joachim T |last2=Haug |first2=Carolin |last3=Maas |first3=Andreas |last4=Kutschera |first4=Verena |last5=Waloszek |first5=Dieter |date=2010 |title=Evolution of mantis shrimps (Stomatopoda, Malacostraca) in the light of new Mesozoic fossils |journal=BMC Evolutionary Biology |language=en |volume=10 |issue=1 |pages=290 |doi=10.1186/1471-2148-10-290 |doi-access=free |issn=1471-2148 |pmc=2955030 |pmid=20858249|bibcode=2010BMCEE..10..290H }}{{Cite journal |last1=Smith |first1=C.P.A. |last2=Aubier |first2=P. |last3=Charbonnier |first3=S. |last4=Laville |first4=T. |last5=Olivier |first5=N. |last6=Escarguel |first6=G. |last7=Jenks |first7=J.F. |last8=Bylund |first8=K.G. |last9=Fara |first9=E. |last10=Brayard |first10=A. |date=2023-03-31 |title=Closing a major gap in mantis shrimp evolution - first fossils of Stomatopoda from the Triassic |url=https://www.researchgate.net/publication/369959650 |journal=Bulletin of Geosciences |language=en |pages=95–110 |doi=10.3140/bull.geosci.1864 |issn=1802-8225}} The results of the analysis from Smith ''et al.'' (2023) are displayed below: {{Cladogram of fossil mantis shrimp genera}} ==Palaeoenvironment== Unlike other known mantis shrimps of the [Paleozoic](/source/Paleozoic) (which lived in [shallow marine](/source/shallow_marine) or [brackish](/source/brackish)-freshwater environments), both species of ''Archaeocaris'' are believed to have inhabited deep water in open seas. There is some overlap in the chronological ranges of the two species, but they occur in different geographic areas and thus would not have coexisted with each other.{{Cite journal |last=Schram |first=Frederick R. |date=1981 |title=Late Paleozoic Crustacean Communities |url=https://www.jstor.org/stable/1304334 |journal=Journal of Paleontology |volume=55 |issue=1 |pages=126–137 |jstor=1304334 |issn=0022-3360}} All known remains of ''A. vermiformis'' were found in Boyle County, Kentucky and originate from deposits at the base of the [Waverly Group](/source/Waverly_Group), dating to the [Tournaisian](/source/Tournaisian) stage of the [Carboniferous](/source/Carboniferous) period ([Kinderhookian](/source/Kinderhookian) stage in the North American regional series, approximately 358.9 to 348 million years ago). The deposits in which this species is found has also preserved fossils of brachiopods (such as ''[Lingula](/source/Lingula_(brachiopod))'', ''[Productus](/source/Productus)'' and ''[Spirifer](/source/Spirifer)''), bivalves (such as ''[Aviculopecten](/source/Aviculopecten)'', ''[Palaeoneilo](/source/Palaeoneilo)'' and ''[Schizodus](/source/Schizodus)''), bryozoans (such as ''[Fenestella](/source/Fenestella_(bryozoan))''), conulariids (such as ''[Conularia](/source/Conularia)'') and crustaceans (such as ''[Palaeopalaemon](/source/Palaeopalaemon)'' and ''[Ceratiocaris](/source/Ceratiocaris)''). This assemblage is indicative of a [benthic](/source/benthic) level community in an open marine environment. The species ''A. graffhami'' has a wider chronological range, with the geologically oldest specimens originating from the upper Pilot Shale of Nevada and dating back to the earliest Kinderhookian (around 358.9 million years ago) of the Tournaisian stage. Remains of [ostracod](/source/ostracod)s, [sponge](/source/sponge)s, and [brachiopod](/source/brachiopod)s are also known from this site.{{Cite journal |last1=Sandberg |first1=C.A. |last2=Poole |first2=F.G. |date=1970 |title=Conodont biostratigraphy and age of West Range Limestone and Pilot Shale at Bactrian Mountain, Pahranagat Range, Nevada |journal=Geological Society of America Abstracts with Programs |volume=2 |issue=2 |pages=139}} In addition, the type specimen of ''A. graffhami'' was collected from the [Caney Shale](/source/Caney_Shale) in Oklahoma, a younger site which dates to the late [Viséan](/source/Vis%C3%A9an) stage (latest [Meramecian](/source/Meramecian) or earliest [Chesteran](/source/Chesteran) stages in the North American regional series, as recently as 330.9 million years ago), making it the youngest known record of the genus. Here, remains of the species are found alongside those of the brachiopod ''[Linoproductus](/source/Linoproductus)'', the bivalve ''[Caneyella](/source/Caneyella)'', several [cephalopod](/source/cephalopod)s and numerous [conodont](/source/conodont)s.{{Cite journal |last1=Elias |first1=M.K. |last2=Branson |first2=C.C. |date=1959 |title=Type Section of the Caney Shale |url=https://ngmdb.usgs.gov/Prodesc/proddesc_91136.htm |journal=Oklahoma Geological Survey |volume=52 |pages=24}} In both the Pilot Shale and Caney Shale, the associated fossil assemblage is largely made up of species typically found in the bottom communities of open deep water, suggesting this was the preferred habitat of ''A. graffhami''. ==References== {{Reflist}} ==External links== {{Portal|Crustaceans|Paleontology}} {{Commons category|Archaeocaris}} {{Wikispecies|Archaeocaris}} {{Taxonbar|from=Q124958811}} Category:Carboniferous animals of North America Category:Stomatopoda Category:Fossil taxa described in 1872 Category:Prehistoric crustacean genera Category:Prehistoric mantis shrimps --- Adapted from the Wikipedia article [Archaeocaris](https://en.wikipedia.org/wiki/Archaeocaris) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Archaeocaris?action=history)). 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