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. Characteristics The structure of the dentine of eriptychiids is in many respects closer to that of heterostracans that to that of astraspids. This is the only argument to place them as the closest relatives to heterostracans, among the Ordovician vertebrates. However, eriptychiids differ from all other pteraspidomorphs in having a massively calcified endoskeleton, pervaded by canals for blood vessels. Taxonomy Order †Eriptychiiformes Ørvig 1958 Genus ?†Eleochera Sansom & Smith 2005 Family †Eriptychiidae Tarlo 1962 Genus †Eriptychius Walcott 1892 Family †Oniscolepididae Märss & Karatajūtė-Talimaa 2009 Genus †Kallostrakon Lankester 1870 Genus †Oniscolepis Pander 1856 non Groß 1961 [Strosipherus Pander 1856]} See also Fish References External links Eriptychiida Pteraspidomorphi Prehistoric jawless fish orders Ordovician jawless fish Late Ordovician animals Ordovician fish of North America Late Ordovician first appearances Late Ordovician taxonomic orders Late Ordovician extinctions de:Pteraspidomorphi#Eriptychiida