Protopteraspididae

Protopteraspididae Temporal range: Early Devonian
Protopteraspis gosseleti
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Infraphylum:	Agnatha
Class:	† Pteraspidomorpha
Subclass:	† Heterostraci
Order:	† Pteraspidiformes
Family:	† Protopteraspididae
Genera
Protopteraspis Doryaspis Escharaspis Miltaspis Stegobranchiaspis Unkaraspis "Trygonaspis"

Protopteraspididae is an extinct family of pteraspidid heterostracan agnathans. Fossils of the various genera are found in early Devonian-aged marine strata. Protopteraspidids were once thought to represent a taxon of basal pteraspidids (hence "proto") but recent evaluations demonstrate that Protopteraspididae is a paraphyletic group of various transitional forms representing a gradual transition between the more advanced Pteraspoidei (comprising Pteraspididae, Gigantaspis and Protaspididae), ^[1] and the anchipteraspidids and the Psammosteids.

Genera

Protopteraspids are found in Lower Devonian marine strata of the Western United States, Northern Canada, England, France, Belgium, Svalbard, Norway, and Podolia, Ukraine. ^[2]

Protopteraspis

This genus is known from several species from Lower Devonian England, France and Belgium

Doryaspis

This is a genus of aberrant pteraspidids with lower lips elongated into long, dagger-like organs of unknown function. The various species are primarily restricted to the Lower Devonian strata of Svalbard.

"Trygonaspis"

"Trygonaspis" is a nomen nudum given to a well-preserved complete armor that strongly resembles Protopteraspis in form, but with a long, recurved dorsal spine, and orbital plates that have bookshelf-like extensions. The only known specimen was found in Northern Canada.^{[ citation needed ]}

References

1. Pernegre, Vincent N., and David K. Elliott. "Phylogeny of the Pteraspidiformes (Heterostraci), Silurian–Devonian jawless vertebrates." Zoologica Scripta 37.4 (2008): 391-403.
2. Blieck, Alain. "Les hétérostracés Ptéraspidiformes, agnathes du Silurien-Dévonien du continent Nord-Atlantique et des blocs avoisinants: Révision systématique, phylogénie, biostratigraphie, biogéographie." (1984).

1. Palaeos Vertebrates entry on order Pteraspidiformes