Taxa Pteraspidiformes

1 taxa

1.1 anchipteraspididae
1.2 psammosteida
1.3 protopteraspididae
1.4 pteraspidoidei

1.4.1 pteraspididae
1.4.2 gigantaspididae
1.4.3 protaspididae

taxa
anchipteraspididae

if weigeltaspis not psammosteid pteraspidid, anchipteraspidids oldest-most known pteraspidid heterostracans, 3 genera pridolian-aged strata upper silurian canada. armor of anchipteraspidids superficially resemble of cyathaspidids, though, anchipteraspidids have typical series of plates diagnostic of pteraspidids, , growth habits of anchipteraspidids diagnostic of pteraspidids, , not of cyathaspidids.

psammosteida

the psammosteids group of pteraspidids forms sister taxon of protopteraspididae , pteraspidoidei, , treated suborder, psammosteida, or family, psammosteidae. anatomically, typical psammosteid resembles typical pteraspidid has had forebody depressed, long, compressed tail. psammosteids, pycnosteus, have ventral shield modified pedestal-like structure researchers compare sled s runner. psammosteids heterostracans survive beyond middle devonian, last genera became extinct during late devonian. late silurian-early devonian genus weigeltaspis may or may not belong group; species of genus superficially resemble small, elongated psammosteid.

protopteraspididae

protopteraspididae once thought family of primitive or basal pteraspidids. recent analysis of pteraspidiformes shows protopteraspididae paraphyletic, various taxa show gradual transition primitive taxa similar anchipteraspidids towards more derived taxa (such panamintaspis) closer pteraspidoidei.

pteraspidoidei

restoration of larnovaspis

pteraspidoidei contains more derived taxa within pteraspidiformes, though, protopteraspidids, such doryaspis , panamintaspis, share various features these derived pteraspidids.

pteraspididae

pteraspididae devonian-aged family contains stereotypical, torpedo-shaped pteraspidids, such type genus, pteraspis, , close relatives errivaspis , rhinopteraspis, popularly thought have actively swam in water column. elongated rostral plate thought hydrodynamic ability. various genera found in various marine , estuarine strata of devonian europe , north america.

gigantaspididae

gigantaspididae monogeneric family erected gigantaspis, genus of pteraspidids restricted devonian marine strata of svalbard. species of gigantaspis superficially resemble genera of sister taxon, protaspididae, i.e., had armor shaped hot bun or round loaf of bread.

protaspididae

protaspididae family of bun or bread loaf-shaped pteraspidids found in devonian marine strata rocky mountains of united states, , of europe. genera, such xylaspis , woodfjordaspis, similar in form gigantaspis, while others, such protaspis , tuberculaspis, have armor more mound-shaped, or psephaspis, compressed form described psammosteid closely related drepanaspis.