Arthrodira

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Arthrodira
Temporal range: Late Silurian? - Late Devonian
Dunkleosteus BW.jpg
Dunkleosteus terrelli
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Placodermi
Order: Arthrodira
Woodward, 1891
Suborders and infraorders

basal

Phlyctaenioidei

Brachythoraci

and see text

Arthrodira is an order of extinct armoured, 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.

Greek for "jointed neck", the arthrodires had movable joint between armor surrounding the head and body. The mouth is interesting because as the lower jaw moved down, the head shield moved, allowing for a large opening. Lacking distinct teeth, like all placoderms, they used the sharpened edges of a bony plate as a biting surface. The eye sockets are protected by a bony ring, 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 3 to as much as 9 m in length. In contrast, the long-nosed Rolfosteus measured just 15 cm.

Heterosteus ingens from the Middle Devonian of Estonia

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.

Systematics[1][edit]

Below is a cladogram from Dupret et al. (2009).[2]



 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
Phlyctaenii

ORDER ARTHRODIRA

Genera incertae sedis[edit]

Arthrodira of unresolved relationships

Timeline of genera[edit]

Devonian Famennian Frasnian Givetian Eifelian Emsian Pragian Lochkovian Trachosteus Stenosteus Paramylostoma Mylostoma Hussakofia Holdenius Gymnotrachelus Gorgonichthys Glyptaspis Bungartius Titanichthys Selenosteus Diplognathus Africanaspis Tafilalichthys Aspidichthys Trematosteus Tapinosteus Synauchenia Rhinosteus Pholidosteus Parabelosteus Pachyosteus Microsteus Leptosteus Erromenosteus Enseosteus Cyrtosteus Braunosteus Brachyosteus Belosteus Oxyosteus Brachydeirus Operchaliosteus Hadrosteus Dinichthys Deveonema Heintzichthys Groenlandaspis Cosmacanthus Callognathus Timanosteus Rolfosteus Platyaspis Megaloplax Malerosteus Latocamurus Dinomylostoma Tubonasus Torosteus Plourdosteus Panxiosteus Melanosteus Mcnamaraspis Machaerognathus Kimberleyichthyes Kimberia Kendrichthys Incisoscutum Harrytoombsia Gyroplacosteus Fallacosteus Eldenosteus Copanognathus Camuropiscis Bullerichthys Bruntonichthys Dunkleosteus Rachiosteus Yinosteus Tropidosteus Rhenonema Kiangyousteus Hollardosteus Heterosteus Eastmanosteus Squamatognathus Deirosteus Holonema Grazosteus Belemnacanthus Arctonema Atlantidosteus Taemasosteus Laurentaspis Williamsaspis Toombsosteus Parabuchanosteus Goodradigbeeon Errolosteus Burrinijucosteus Buchanosteus Arenipiscis Stuertzaspis Gemuendenaspis Tiaraspis Taunaspis Murmur Kweichowlepis Wheathillaspis Prescottaspis Overtonaspis Eskimaspis Qataraspis Devonian Famennian Frasnian Givetian Eifelian Emsian Pragian Lochkovian

Footnotes[edit]

  1. ^ For sources, see Haaramo (2005)
  2. ^ Dupret, V.; Zhu, M. I. N.; Wang, J. N. Q. (2009). "The morphology ofYujiangolepis 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.  edit

See also[edit]

List of placoderms

References[edit]

External links[edit]