| Eriptychiida | |
|---|---|
 | |
| Specimen ofEriptychius americanus | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Infraphylum: | Agnatha |
| Class: | †Pteraspidomorpha |
| Subclass: | †Heterostracomorphi |
| Infraclass: | †Eriptychiida Tarlo 1962 |
| Order: | †Eriptychiiformes Ørvig 1958[1] |
| Families | |
Eriptychiida is anextinctmarinetaxon ofvertebrate in the groupPteraspidomorphi.
The order contains thegenus,Eriptychius, andfossilizedspecimens from this genus have been found in theGull River Formation ofOntario, theHarding Formation ofColorado, and theBighorn Dolomite ofWyoming. The group contains two documentedspecies:Eriptychius americanus andEriptychius orvigi.
The structure of the dentine of eriptychiids is in many respects closer to that ofheterostracans that to that ofastraspids. 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 underVertebrata, not considering class or order.[6]
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