Protaspididae is an extinct

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

pteraspidid Pteraspididae is an extinct family of heterostracan vertebrates. It is an Early Devonian-aged family that contains the stereotypical, torpedo-shaped pteraspidids, such as the type genus, ''Pteraspis'', and its close relatives '' Errivaspis'' and ...

heterostracan Heterostraci (Ancient Greek, ἕτερος+ὄστρακον "those itha different shell" i is pl. of -us is an extinct subclass of pteraspidomorph jawless vertebrate that lived primarily in marine and estuary environments. Heterostraci exi ...

agnatha Agnatha (, Ancient Greek 'without jaws') is an infraphylum of jawless fish in the phylum Chordata, subphylum Vertebrata, consisting of both present (cyclostomes) and extinct ( conodonts and ostracoderms) species. Among recent animals, cyclosto ...

ns. Fossils of the various genera are found in early

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

-aged marine strata. Protaspidids were once thought to represent a transitional form between the

Pteraspididae Pteraspididae is an extinct family of heterostracan vertebrates. It is an Early Devonian-aged family that contains the stereotypical, torpedo-shaped pteraspidids, such as the type genus, ''Pteraspis'', and its close relatives ''Errivaspis'' and ' ...

and the

Psammosteida Psammosteida also called as Psammosteoidei is a suborder of pteraspidid heterostracan agnathans. The psammosteids had broad, flattened bodies, suggesting a predominantly benthic habit. The earliest unequivocal psammosteid is '' Drepanaspis'' of ...

, bearing the broad head shield shape of the latter, due to a more

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...

(bottom-dwelling) existence, but recent phylogenical comparisons demonstrate that the protaspidids are actually highly derived pteraspidids,Pernegre, Vincent N., and David K. Elliott. "Phylogeny of the Pteraspidiformes (Heterostraci), Silurian–Devonian jawless vertebrates." Zoologica Scripta 37.4 (2008): 391-403. and that the anchipteraspidids, the most primitive of pteraspidids, are the sister-group of the Psammosteids.

Genera

Many genera are found in Lower Devonian marine deposits of the United States, especially of Utah and Wyoming. Others are found in Lower Devonian marine strata of Europe, especially of

Svalbard Svalbard ( , ), also known as Spitsbergen, or Spitzbergen, is a Norwegian archipelago in the Arctic Ocean. North of mainland Europe, it is about midway between the northern coast of Norway and the North Pole. The islands of the group range ...

Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and t ...

, and

Podolia Podolia or Podilia ( uk, Поділля, Podillia, ; russian: Подолье, Podolye; ro, Podolia; pl, Podole; german: Podolien; be, Падолле, Padollie; lt, Podolė), is a historic region in Eastern Europe, located in the west-central ...

Ukraine Ukraine ( uk, Україна, Ukraïna, ) is a country in Eastern Europe. It is the second-largest European country after Russia, which it borders to the east and northeast. Ukraine covers approximately . Prior to the ongoing Russian inv ...

.Blieck, Alain. "Les hétérostracés Ptéraspidiformes, agnathes du Silurien-Dévonien du continent Nord-Atlantique et des blocs avoisinants: Révision systématique, phylogénie, biostratigraphie, biogéographie." (1984).

''Protaspis''

This genus is known from several species from the Early Devonian-aged Beartooth Butte Formation strata of Wyoming and Utah. ''Europrotaspis'', ''Cosmaspis'', ''Lampraspis'', '' Gigantaspis'', ''Eucyclaspis'', and ''Cyrtaspidithchys'' have been formerly placed within ''Protaspis'' as subgenera, or otherwise have been treated as species therein.Denison, Robert Howland. ''Revised classification of Pteraspididae with description of new forms from Wyoming.'' Field Museum of Natural History, 1970.

''Europrotaspis''

Species of this genus are very similar to those of ''Protaspis'', but, are found in Early Devonian-aged strata of Western Europe and Podolia, Ukraine.

''Eucyclaspis''

Species of ''Eucyclaspis'' are found in marine strata of the Water Canyon Formation, in Lower Devonian Utah. This genus differs from ''Protaspis'' by having unique processes emanating behind the eye on the orbital plate.

''Cosmaspis''

''Cosmaspis'' is restricted to marine environments of Early Devonian Wyoming, and possibly of Utah, as well, where it coexisted with species of ''Protaspis'', ''Lampraspis'', ''Eucyclaspis'', ''Oreaspis'' and ''Cyrtaspidichthys''.

''Lampraspis''

''Lampraspis'' is known from Early Devonian-aged marine environments of Utah and Wyoming. It is closely related to ''Oreaspis'' and ''Psephaspis'', and the three genera were, at one time, placed together in a subfamily, "Oreaspidinae."

''Cyrtaspidichthys''

Species of ''Cyrtaspidichthys'', originally "Cyrtaspis," are very similar to those of ''Protaspis''. Fossils of ''Cyrtaspidichthys'' are found in Early Devonian-aged marine strata of Beartooth Butte, Wyoming.

''Oreaspis''

''Oreaspis'' differs from ''Protaspis'' in ornamentation, and that the postbranchial plate (the plate posterior to the exhalant opening of the animal's gills) forms a tiny, wing-like process. Species of ''Oreaspis'' are found in Early Devonian marine strata of Water Canyon, Utah, and Beartooth Butte of Wyoming. At one time, this genus, together with ''Lampraspis'' and ''Psephaspis'', was placed within its own subfamily, "Oreaspidinae."

''Psephaspis''

Species of ''Psephaspis'', which are restricted to Idaho and Utah, have broad, flat, rounded and heart-shaped dorsal shields, and ornamentation similar to those of psammosteids. Because of these two traits, species of this genus were originally described as being North American psammosteids closely related to ''Drepanaspis'' by Orvig. Denison then redescribed them as being pteraspidids closely related to ''Protaspis'', noting that the overall anatomy is that of a typical pteraspidid. Denison also notes that ''Psephaspis'' is the youngest genus of pteraspidid, as specimens of ''P. idahoensis'' are found in Middle Devonian-aged strata of Lemhi County, Idaho, which are younger than the latest strata other pteraspidids are found in.

''Rodenaspis''

This genus was established by Blieck in 1984 when he elevated ''Protaspis (Protaspis) brevispina'' into a separate genus, noting its cornual processes are distinct from ''Protaspis''.

''Tuberculaspis''

''Tuberculaspis'' is known from Early Devonian marine strata of

Nevada Nevada ( ; ) is a U.S. state, state in the Western United States, Western region of the United States. It is bordered by Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast, and Utah to the east. N ...

, where it coexisted sympatrically with the protopteraspidid '' Lamiaspis'', and fellow protaspid '' Pirumaspis'' in a shallow-water marine environment. It is named for tubercule-like growths that decorate the borders of its dorsal shield.Ilyes, Robert R., and David K. Elliott. "New Early Devonian pteraspidids (Agnatha, Heterostraci) from East-central Nevada." Journal of Paleontology(1994): 878-892.

''Xylaspis''

This

Spitzbergen Svalbard ( , ), also known as Spitsbergen, or Spitzbergen, is a Norwegian archipelago in the Arctic Ocean. North of mainland Europe, it is about midway between the northern coast of Norway and the North Pole. The islands of the group range ...

protaspid was originally named '' Spitsbergaspis'', but that name was discovered to be preoccupied by an Ordovician trilobite. It is similar in form and related to ''Zascinaspis'' and ''Woodfjordaspis''.

''Zascinaspis''

Species of ''Zascinaspis'' are found in Early Devonian marine strata of Spitzbergen, and are similar in form to ''Xylaspis'', ''Woodfjordaspis'' and '' Gigantaspis'', the former two genera being closely related.

''Woodfjordaspis''

''Woodfjordaspis'' is known from an incomplete, partially articulated armor found in early Devonian-aged marine strata of Spitzbergen. It is similar in form and is closely related to ''Zascinaspis'' and ''Xylaspis''.

''Pirumaspis''

This protaspid is from the Sevy Dolomite Fauna of Late Emsian-aged marine strata in Nevada, where it coexisted sympatrically with ''Tuberculaspis'', and the protopteraspidid ''Lamiaspis''.

References

Palaeos Vertebrates entry on order Pteraspidiformes
{{Taxonbar, from=Q7251190 Pteraspidiformes Devonian jawless fish Early Devonian fish Prehistoric jawless fish families Early Devonian first appearances Early Devonian extinctions