The largest member of this group, Dunkleosteus, was a true superpredator of the latest Devonian period, reaching as much as 6 m in length.

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 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.

[9] Eurycaraspis incilis Lunaspis broilii Yujiangolepis liujingensis Antarctaspis mcmurdoensis 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 Gavinaspis convergens Austrophyllolepis sp.