Arthrodira

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Arthrodira
Temporal range: Devonian, 419.2–358.9  Ma
D Terrelli.png
Artist's reconstruction of the arthrodire placoderm Dunkleosteus terrelli
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Infraphylum: Gnathostomata
Class: Placodermi
Order: Arthrodira
Woodward, 1891
Subgroups

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]

Contents

Description

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 ]

Evolution and extinction of placoderms. The diagram is based on Michael Benton, 2005. Evolution of placoderms.png
Evolution and extinction of placoderms. The diagram is based on Michael Benton, 2005.

Phylogeny

The 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]

Lunaspis broilii

Eurycaraspis incilis

Arthrodira

Yujiangolepis liujingensis

Antarctaspis mcmurdoensis

Wuttagoonaspidae

Yiminaspis shenme

Wuttagoonaspis fletcheri

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

Phyllolepis orvini

Austrophyllolepis sp.

Cowralepis mclachlani

Placolepis budawangensis

Actinolepidae

Bollandaspis woschmidti

Actinolepis spinosa

Actinolepis magna

Actinolepis tuberculata

Bryantolepis brachycephalus

Phlyctaenioidei
Phlyctaeniidae

Phlyctaenius acadicus

Pageauaspis russelli

Groenlandaspidae

Groenlandaspis antarctica

Tiaraspis subilis

Arctaspidae

Dicksonosteus arcticus

Arctolepidae

Arctolepis decipiens

Heintzosteus brevis

Brachythoraci

Antineosteus lehmani

Buchanosteus confertituberculatus

Coccosteus cuspidatus

Actinolepidoidei
Phlyctaeniina

Classification

The pelagic selenosteid Amazichthys trinajsticae Amazichthys.jpg
The pelagic selenosteid Amazichthys trinajsticae
Artist's reconstruction of the arthrodire placoderm Coccosteus cuspidatus C cuspidatus.png
Artist's reconstruction of the arthrodire placoderm Coccosteus cuspidatus
Lower jaw plate of Eastmanosteus pustulosus from the Middle Devonian of Wisconsin Eastmanosteus pustulosus.jpg
Lower jaw plate of Eastmanosteus pustulosus from the Middle Devonian of Wisconsin
Heterosteus ingens from the Middle Devonian of Estonia Heterosteus ingens.jpg
Heterosteus ingens from the Middle Devonian of Estonia

Order ArthrodiraWoodward, 1891

Related Research Articles

<i>Dunkleosteus</i> Genus of extinct fishes

Dunkleosteus is an extinct genus of large arthrodire ("jointed-neck") fish that existed during the Late Devonian period, about 382–358 million years ago. It was a pelagic fish inhabiting open waters, and one of the first apex predators of any ecosystem.

<i>Coccosteus</i>

Coccosteus is an extinct genus of arthrodire placoderm from the Devonian period. Its fossils have been found throughout Europe and North America. The majority of these have been found in freshwater sediments, though such a large range suggests that they may have been able to enter saltwater. It was a small placoderm, with Coccosteus cuspidatus measuring 29.6–43.9 cm (11.7–17.3 in) long.

<i>Dinichthys</i> Extinct genus of placoderm fish

Dinichthys is an extinct monospecific genus of large marine arthrodire placoderm from the Late Devonian measuring around 3 metres (9.8 ft) long. Fossils were recovered from the Ohio Shale Formation along the Olentangy River in Delaware County, Ohio.

<span class="mw-page-title-main">Dunkleosteidae</span> Extinct family of fishes

Dunkleosteidae is an extinct family of arthrodire placoderms that lived during the Devonian period. The gigantic apex predator Dunkleosteus terrelli is the best known member of this group.

<i>Arctolepis</i> Extinct genus of fishes

Arctolepis is an extinct genus of placoderm arthrodire fish which lived during the Early Devonian period. Fossils of Arctolepis have been found in what is now Norway and Michigan.

<span class="mw-page-title-main">Phlyctaeniidae</span> Extinct family of fishes

Phlyctaeniidae is an extinct family of placoderm arthrodire fishes that lived during the Devonian period, mainly in Norway and North America.

<i>Dicksonosteus</i> Extinct genus of fishes

Dicksonosteus is an extinct genus of basal arthrodire placoderm fish which lived during the Early Devonian period of Spitsbergen, Norway.

Heintzosteus is an extinct genus of placoderm arthrodire fish, which lived during the Late Devonian period in Spitsbergen, Norway.

<i>Plourdosteus</i> Extinct genus of fishes

Plourdosteus is an extinct genus of placoderm arthrodire which was relatively widespread in Euramerica during the Givetian to Frasnian ages of the Devonian. It was a small placoderm, with P. canadensis measuring 37.5–51.4 cm (14.8–20.2 in) long.

<i>Mcnamaraspis</i>

Mcnamaraspis is an extinct monospecific genus of arthrodire placoderm that inhabited the ancient reef system of north Western Australia during the Frasnian epoch of the Late Devonian period. The type specimen was found and described by John A. Long from the Gogo Formation near Fitzroy Crossing. This fossil fish showed new anatomical features in arthrodires, like the well-preserved annular (ring-shaped) cartilages of the snout, previously inferred to be present by Erik Stensiö of Sweden. It is occasionally referred to as "The Gogo Fish" after the locale the holotype was excavated from.

<span class="mw-page-title-main">Homostiidae</span>

Homostiidae is a family of flattened arthrodire placoderms from the Early to Middle Devonian. Fossils appear in various strata in Europe, Russia, Morocco, Australia, Canada and Greenland.

<span class="mw-page-title-main">Dunkleosteoidea</span> Extinct superfamily of fishes

Dunkleosteoidea is an extinct superfamily of arthrodire placoderms that lived during the Devonian period. The gigantic apex predator Dunkleosteus terrelli is the best known member of this group.

<i>Kujdanowiaspis</i>

Kujdanowiaspis is an extinct genus of actinolepid placoderm from the Early Devonian of Podolia (Ukraine), Poland and Spain. Kujdanowiaspis is known from many fragmentary head shields and body armours. After revision of the Podolian material, three species in two genera were recognized: Kujdanowiaspis buczacziensis (type-species), Kujdanowiapsis podolica and Erikaspis zychi.

<span class="mw-page-title-main">Eubrachythoraci</span> Extinct suborder of fishes

Eubrachythoraci is an extinct clade of arthrodire placoderms within the suborder Brachythoraci, armored fish most diverse during the Devonian. Most are considered to be pelagic long-distance swimmers, leading to their widespread distribution beginning from at least the Middle Devonian period.

<span class="mw-page-title-main">Pachyosteomorphi</span> Extinct suborder of fishes

Pachyosteomorphi is an extinct clade of arthrodire placoderms within the Eubrachythoraci, armored fish most diverse during the Devonian. Most are considered to be pelagic long-distance swimmers, leading to their widespread distribution beginning from at least the Middle Devonian period.

Panxiosteus is an extinct monospecific genus of placoderm arthrodire from the Middle Devonian: Givetian stage of Yunnan province, China.

<span class="mw-page-title-main">Coccosteomorphi</span> Extinct suborder of fishes

Coccosteomorphi is an extinct clade of arthrodire placoderms within the Eubrachythoraci, armored fish most diverse during the Devonian. Most are considered to be pelagic long-distance swimmers, leading to their widespread distribution beginning from at least the Middle Devonian period.

<i>Millerosteus</i> Extinct genus of placoderm fish of the Devonian period

Millerosteus is an extinct genus of coccosteid arthrodire placoderm from the Early Givetian stage of the Middle Devonian period. Fossils are found in the Orkneys and Caithness, Scotland. It was a small placoderm with an body length of 14 cm (5.5 in). Millerosteus is one of the few arthrodires known from specimens preserving the entire skeleton.

Dickosteus is an extinct genus of coccosteid arthrodire placoderm from the Late Eifelian to Early Givetian stages of the Middle Devonian period. Fossils are found in the Orkneys and Caithness, Scotland. It was a small placoderm with a total body length of 43.7–52.3 cm (17.2–20.6 in). It is one of the few placoderms for which complete bodies are known.

<i>Watsonosteus</i>

Watsonosteus is an extinct genus of coccosteid arthrodire placoderm from the Late Givetian stage of the Middle Devonian period. Fossils are found in the Orkney Islands, Scotland. It was a small placoderm with a total body length of 57 cm (22 in), with the largest individuals reaching lengths of 1 m (39 in). It is one of the few arthrodires for which complete body fossils are known.

References

  1. 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.
  2. 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.
  3. "Fish 380 Million Years Old Found With Unborn Embryo". Science Daily. June 6, 2008.
  4. 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.
  5. Benton, M. J. (2005) Vertebrate Palaeontology, Blackwell, 3rd edition, Figure 3.25 on page 73.
  6. Closed Access logo transparent.svg 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.
  7. 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.
  8. 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.
  9. 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