Arthrodira (Greek for "jointed neck") is an order of extinct armored, jawed fishes of the class Placodermi that flourished in the Devonian period before their sudden extinction, surviving for about 50 million years and penetrating most marine ecological niches. Arthrodires were the largest and most diverse of all groups of placoderms.[1]
Arthrodire placoderms are notable for the movable joint between armor surrounding their heads and bodies. Like all placoderms, they lacked distinct teeth; instead, they used the sharpened edges of a bony plate on their jawbone as a biting surface. The eye sockets are covered by a bony ring, which supports the eye, a feature shared by birds and some ichthyosaurs. Early arthrodires, such as the genus Arctolepis, were well-armoured fishes with flattened bodies. The largest member of this group, Dunkleosteus, was a true superpredator of the latest Devonian period, reaching as much as 6 m in length. In contrast, the long-nosed Rolfosteus measured just 15 cm.[2] Fossils of Incisoscutum have been found containing unborn fetuses, indicating that arthrodires gave birth to live young.[3][4]
A common misconception is the arthrodires (along with all other placoderms) were sluggish bottom-dwellers that were outcompeted by more advanced fish. Leading to this misconception is that the arthrodire body plan remained relatively conserved (that is, the majority of arthrodires were bullet- or torpedo-shaped) during the Devonian period, save for increasing in size. However, during their reign, the arthrodires were one of the most diverse and numerically successful, if not the most successful, vertebrate orders of the Devonian, occupying a vast spectrum of roles from apex predator to detritus-nibbling bottom dweller. Despite their success, the arthrodires were one of many groups eliminated by the environmental catastrophes of the Late Devonian extinction, allowing other fish such as sharks to diversify into the vacated ecological niches during the Carboniferous period.[citation needed]
The order Arthrodira belongs to the classPlacodermi, the large group of extinct prehistoric armored fish that is thought to have diverged over 400 million years ago from all sharks and bony fishes (and thus also all subsequent tetrapods, including mammals, birds, reptiles and amphibians). However, recent phylogenetic studies have found Placodermi to be paraphyletic, and rather an evolutionary grade towards Eugnathostomata, the clade grouping that contains sharks, bony fish, and all tetrapods.[6][7]
Arthrodira was traditionally divided into the paraphyletic Actinolepida, the Phlyctaenii (now also paraphyletic), and the Brachythoraci.[8]Phylogenetic studies have since found two of those groups as paraphyletic, as shown in the cladogram below, from Dupret et al. (2009).[9]
Trachosteus Newberry, 18903 (may be within Coccosteidae)
Wheathillaspis White, 1961
Yujiangolepis Wang & Dupret, 2009 (previously within Antarctaspididae)
Referencesedit
^Zhu, You-An; Zhu, Min; Wang, Jun-Qing (1 April 2016). "Redescription of Yinostius major (Arthrodira: Heterostiidae) from the Lower Devonian of China, and the interrelationships of Brachythoraci". Zoological Journal of the Linnean Society. 176 (4): 806–834. doi:10.1111/zoj.12356. ISSN 0024-4082.
^Dennis, Kim, and R. S. Miles. "Eubrachythoracid arthrodires with tubular rostral plates from Gogo, Western Australia." Zoological Journal of the Linnean Society 67.4 (1979): 297–328.
^"Fish 380 Million Years Old Found With Unborn Embryo". Science Daily. June 6, 2008.
^Long, John A.; Trinajstic, Kate; Johanson, Zerina (26 February 2009). "Devonian arthrodire embryos and the origin of internal fertilization in vertebrates". Nature. 457 (7233): 1124–1127. Bibcode:2009Natur.457.1124L. doi:10.1038/nature07732. PMID 19242474. S2CID 205215898.
^Benton, M. J. (2005) Vertebrate Palaeontology, Blackwell, 3rd edition, Figure 3.25 on page 73.
^ Giles, Sam; Friedman, Matt; Brazeau, Martin D. (2015-01-12). "Osteichthyan-like cranial conditions in an Early Devonian stem gnathostome". Nature. 520 (7545): 82–85. Bibcode:2015Natur.520...82G. doi:10.1038/nature14065. ISSN 1476-4687. PMC5536226. PMID 25581798.
^You-An Zhu; Min Zhu (2013). "A redescription of Kiangyousteus yohii (Arthrodira: Eubrachythoraci) from the Middle Devonian of China, with remarks on the systematics of the Eubrachythoraci". Zoological Journal of the Linnean Society. 169 (4): 798–819. doi:10.1111/zoj12089.
^Dupret, V.; Zhu, M. I. N.; Wang, J. N. Q. (2009). "The morphology of Yujiangolepis liujingensis (Placodermi, Arthrodira) from the Pragian of Guangxi (south China) and its phylogenetic significance". Zoological Journal of the Linnean Society. 157: 70. doi:10.1111/j.1096-3642.2009.00519.x.
Further readingedit
Long, John A. (1996): The Rise of Fishes: 500 Million Years of Evolution. Johns Hopkins University Press, Baltimore. ISBN0-8018-5438-5
January 01, 1970
arthrodira, greek, jointed, neck, order, extinct, armored, jawed, fishes, class, placodermi, that, flourished, devonian, period, before, their, sudden, extinction, surviving, about, million, years, penetrating, most, marine, ecological, niches, arthrodires, we. Arthrodira Greek for jointed neck is an order of extinct armored jawed fishes of the class Placodermi that flourished in the Devonian period before their sudden extinction surviving for about 50 million years and penetrating most marine ecological niches Arthrodires were the largest and most diverse of all groups of placoderms 1 ArthrodiraTemporal range Devonian 419 2 358 9 Ma PreꞒ Ꞓ O S D C P T J K Pg N Artist s reconstruction of the arthrodire placoderm Dunkleosteus terrelli Scientific classification Domain Eukaryota Kingdom Animalia Phylum Chordata Infraphylum Gnathostomata Class Placodermi Order ArthrodiraWoodward 1891 Subgroups Phlyctaenioidei Brachythoraci Williamsaspididae Groenlandaspididae Arctolepididae Phlyctaeniidae Actinolepidae Phyllolepida Wuttagoonaspidae Genera incertae sedis see text for list Contents 1 Description 2 Phylogeny 3 Classification 4 References 5 Further readingDescription editArthrodire placoderms are notable for the movable joint between armor surrounding their heads and bodies Like all placoderms they lacked distinct teeth instead they used the sharpened edges of a bony plate on their jawbone as a biting surface The eye sockets are covered by a bony ring which supports the eye a feature shared by birds and some ichthyosaurs Early arthrodires such as the genus Arctolepis were well armoured fishes with flattened bodies The largest member of this group Dunkleosteus was a true superpredator of the latest Devonian period reaching as much as 6 m in length In contrast the long nosed Rolfosteus measured just 15 cm 2 Fossils of Incisoscutum have been found containing unborn fetuses indicating that arthrodires gave birth to live young 3 4 A common misconception is the arthrodires along with all other placoderms were sluggish bottom dwellers that were outcompeted by more advanced fish Leading to this misconception is that the arthrodire body plan remained relatively conserved that is the majority of arthrodires were bullet or torpedo shaped during the Devonian period save for increasing in size However during their reign the arthrodires were one of the most diverse and numerically successful if not the most successful vertebrate orders of the Devonian occupying a vast spectrum of roles from apex predator to detritus nibbling bottom dweller Despite their success the arthrodires were one of many groups eliminated by the environmental catastrophes of the Late Devonian extinction allowing other fish such as sharks to diversify into the vacated ecological niches during the Carboniferous period citation needed nbsp Evolution and extinction of placoderms The diagram is based on Michael Benton 2005 5 Phylogeny editThe order Arthrodira belongs to the class Placodermi the large group of extinct prehistoric armored fish that is thought to have diverged over 400 million years ago from all sharks and bony fishes and thus also all subsequent tetrapods including mammals birds reptiles and amphibians However recent phylogenetic studies have found Placodermi to be paraphyletic and rather an evolutionary grade towards Eugnathostomata the clade grouping that contains sharks bony fish and all tetrapods 6 7 Arthrodira was traditionally divided into the paraphyletic Actinolepida the Phlyctaenii now also paraphyletic and the Brachythoraci 8 Phylogenetic studies have since found two of those groups as paraphyletic as shown in the cladogram below from Dupret et al 2009 9 Eurycaraspis incilis Lunaspis broilii Arthrodira Yujiangolepis liujingensis Antarctaspis mcmurdoensis Wuttagoonaspidae Wuttagoonaspis fletcheri Yiminaspis shenme Aethaspis major Aethaspis utahensis Lehmanosteus hyperboreus Aleosteus eganensis Simblaspis cachensis Kujdanowiaspis buczacziensis Kujdanowiaspis podolica Erikaspis zychi Sigaspis lepidophora Eskimaspis heintzi Baringaspis dineleyi Proaethaspis ohioensis Anarthraspis chamberlini Heightingtonaspis anglica Phyllolepida Gavinaspis convergens Austrophyllolepis sp Cowralepis mclachlani Phyllolepis orvini Placolepis budawangensis Actinolepidae Bollandaspis woschmidti Actinolepis spinosa Actinolepis magna Actinolepis tuberculata Bryantolepis brachycephalus Phlyctaenioidei Phlyctaeniidae Pageauaspis russelli Phlyctaenius acadicus Groenlandaspidae Groenlandaspis antarctica Tiaraspis subilis Arctaspidae Dicksonosteus arcticus Arctolepidae Arctolepis decipiens Heintzosteus brevis Brachythoraci Antineosteus lehmani Buchanosteus confertituberculatus Coccosteus cuspidatus Actinolepidoidei PhlyctaeniinaClassification edit nbsp The pelagic selenosteid Amazichthys trinajsticae nbsp Artist s reconstruction of the arthrodire placoderm Coccosteus cuspidatus nbsp Lower jaw plate of Eastmanosteus pustulosus from the Middle Devonian of Wisconsin nbsp Heterosteus ingens from the Middle Devonian of Estonia Order Arthrodira Woodward 1891 Phlyctaenioidei Miles 1973 Brachythoraci Gross 1932 includes the well known Dunkleosteus Dinichthys etc Williamsaspididae White 1952 Groenlandaspididae Obruchev 1964 Arctolepididae Heintz 1937 Phlyctaeniidae Fowler 1947 Actinolepidae Gross 1940 Phyllolepida Stensio 1934 Wuttagoonaspidae Ritchie 1973 Genera incertae sedis Aethaspis Denison 1958 may be within Actinolepidae Aleosteus Johnson et al 2000 may be within Actinolepidae Anarthraspis Bryant 1934 may be within Actinolepidae Antarctaspis White 1968 previously within Antarctaspididae Antarctolepis White 1968 Aspidichthys Newberry 1873 Baringaspis Miles 1973 may be within Actinolepidae Bryantolepis Denison 1958 may be within Actinolepidae Callognathus Newberry 1890 Copanognathus Hussakof amp Bryant 1920 Carolowilhelmina Mark Kurik amp Carls 2002 Diplognathus Newberry 1878 Erikaspis Dupret Goujet amp Mark Kurik 2007 Eskimaspis Dineley amp Yuhai 1984 Glyptaspis Newberry 1890 Grazosteus Gross 1958 Heightingtonaspis White 1969 may be within Actinolepidae Hollardosteus Lehman 1956 Kujdanowiaspis Stensio 1942 may be within Actinolepidae Lataspis Strand 1932 may be within Actinolepidae Laurentaspis Pageau 1969 Lehmanosteus Goujet 1984 may be within Actinolepidae Machaerognathus Hussakof amp Bryant 1919 Maideria Lelievre 1995 Mediaspis Heintz 1929 may be within Actinolepidae Murmur Whitley 1951 Overtonaspis White 1961 Phylactaenium Heintz 1934 Pinguosteus Long 1990 may be within Brachythoraci Prescottaspis White 1961 Proaethaspis Denison 1978 may be within Actinolepidae Qataraspis White 1969 Sigaspis Goujet 1973 may be within Actinolepidae Simblaspis Denison 1958 may be within Actinolepidae Taunaspis Schmidt 1933 Timanosteus Obrucheva 1962 Trachosteus Newberry 18903 may be within Coccosteidae Wheathillaspis White 1961 Yujiangolepis Wang amp Dupret 2009 previously within Antarctaspididae References edit Zhu You An Zhu Min Wang Jun Qing 1 April 2016 Redescription of Yinostius major Arthrodira Heterostiidae from the Lower Devonian of China and the interrelationships of Brachythoraci Zoological Journal of the Linnean Society 176 4 806 834 doi 10 1111 zoj 12356 ISSN 0024 4082 Dennis Kim and R S Miles Eubrachythoracid arthrodires with tubular rostral plates from Gogo Western Australia Zoological Journal of the Linnean Society 67 4 1979 297 328 Fish 380 Million Years Old Found With Unborn Embryo Science Daily June 6 2008 Long John A Trinajstic Kate Johanson Zerina 26 February 2009 Devonian arthrodire embryos and the origin of internal fertilization in vertebrates Nature 457 7233 1124 1127 Bibcode 2009Natur 457 1124L doi 10 1038 nature07732 PMID 19242474 S2CID 205215898 Benton M J 2005 Vertebrate Palaeontology Blackwell 3rd edition Figure 3 25 on page 73 nbsp Giles Sam Friedman Matt Brazeau Martin D 2015 01 12 Osteichthyan like cranial conditions in an Early Devonian stem gnathostome Nature 520 7545 82 85 Bibcode 2015Natur 520 82G doi 10 1038 nature14065 ISSN 1476 4687 PMC 5536226 PMID 25581798 Zhu Min Ahlberg Per E Pan Zhaohui Zhu Youan Qiao Tuo Zhao Wenjin Jia Liantao Lu Jing 21 October 2016 A Silurian maxillate placoderm illuminates jaw evolution Science 354 6310 334 336 Bibcode 2016Sci 354 334Z doi 10 1126 science aah3764 PMID 27846567 S2CID 45922669 You An Zhu Min Zhu 2013 A redescription of Kiangyousteus yohii Arthrodira Eubrachythoraci from the Middle Devonian of China with remarks on the systematics of the Eubrachythoraci Zoological Journal of the Linnean Society 169 4 798 819 doi 10 1111 zoj12089 Dupret V Zhu M I N Wang J N Q 2009 The morphology of Yujiangolepis liujingensis Placodermi Arthrodira from the Pragian of Guangxi south China and its phylogenetic significance Zoological Journal of the Linnean Society 157 70 doi 10 1111 j 1096 3642 2009 00519 x Further reading editLong John A 1996 The Rise of Fishes 500 Million Years of Evolution Johns Hopkins University Press Baltimore ISBN 0 8018 5438 5 Retrieved from https en wikipedia org w index php title Arthrodira amp oldid 1218835151, wikipedia, wiki, book, books, library,
