Eriptychiida Temporal range: Late Ordovician, | |
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Specimen of Eriptychius americanus | |
Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Subphylum: | Vertebrata |
Infraphylum: | Agnatha |
Class: | † Pteraspidomorpha |
Subclass: | † Heterostracomorphi |
Infraclass: | † Eriptychiida Tarlo 1962 |
Order: | † Eriptychiiformes Ørvig 1958 [1] |
Families | |
Eriptychiida is an extinct marine taxon of vertebrate in the group Pteraspidomorphi.
The order contains the genus, Eriptychius , and fossilized specimens from this genus have been found in the Gull River Formation of Ontario, the Harding Formation of Colorado, and the Bighorn Dolomite of Wyoming. The group contains two documented species: Eriptychius americanus and Eriptychius orvigi.
The structure of the dentine of eriptychiids is in many respects closer to that of heterostracans than to that of astraspids. This is the only argument to place them, as the closest relatives to heterostracans, among the Ordovician vertebrates. A 450 million years old fossil of eriptychius shows it had a skull consisting of separate cartilage plates, with the frontal plates being mineralized, and that a thin body armor covered the head. It appears to be the first step towards a more solid braincase in vertebrates. [2]
In study at 2023, Eriptychius is placed just under Vertebrata, not considering class or order. [6]