| 词条 | Eriptychiida |
| 释义 |
| name = Eriptychiida | image = | image_caption = | fossil_range = Late Ordovician, {{Fossil range|450}} | regnum = Animalia | phylum = Chordata | classis = †Pteraspidomorphi | subclassis = †Heterostracomorphi | ordo = †Eriptychiida }} Eriptychiida is an extinct marine taxon of vertebrate in the group Pteraspidomorphi. The order contains only one 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 only two documented species: Eriptychius americanus and Eriptychius orvigi. CharacteristicsThe 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. See also
External links
8 : 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 |
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