Protopteraspididae is an extinct

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

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'' a ...

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, cyclos ...

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, w ...

-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 In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

group of various transitional forms representing a gradual transition between the more advanced Pteraspoidei (comprising Pteraspididae, '' Gigantaspis'' and

Protaspididae Protaspididae is an extinct family of pteraspidid heterostracan agnathans. Fossils of the various genera are found in early Devonian-aged marine strata. Protaspidids were once thought to represent a transitional form between the Pteraspididae ...

),Pernegre, Vincent N., and David K. Elliott. "Phylogeny of the Pteraspidiformes (Heterostraci), Silurian–Devonian jawless vertebrates." Zoologica Scripta 37.4 (2008): 391-403. and the anchipteraspidids and the Psammosteids.

Genera

Protopteraspids are found in Lower Devonian marine strata of the Western

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, Northern

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Belgium Belgium, ; french: Belgique ; german: Belgien officially the Kingdom of Belgium, is a country in Northwestern Europe. The country is bordered by the Netherlands to the north, Germany to the east, Luxembourg to the southeast, France to ...

, Svalbard,

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, 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 invas ...

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

''Protopteraspis''

This genus is known from several species from Lower Devonian

and

''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.

''Escharaspis''

''Miltaspis''

''Stegobranchiaspis''

''Unarkaspis''

"Trygonaspis"

"Trygonaspis" is a ''

nomen nudum In taxonomy, a ''nomen nudum'' ('naked name'; plural ''nomina nuda'') is a designation which looks exactly like a scientific name of an organism, and may have originally been intended to be one, but it has not been published with an adequate des ...

'' given to a beautifully preserved complete armor that strongly resembles ''Protopteraspis'' in form, but with a long, recurved dorsal spine, and

orbital Orbital may refer to: Sciences Chemistry and physics * Atomic orbital * Molecular orbital * Hybrid orbital Astronomy and space flight * Orbit ** Earth orbit Medicine and physiology * Orbit (anatomy), also known as the ''orbital bone'' * Orbito ...

plates that have bookshelf-like extensions. The only known specimen was found in Northern Canada.

References

Palaeos Vertebrates entry on order Pteraspidiformes
Pteraspidiformes Devonian jawless fish Early Devonian fish Prehistoric jawless fish families Early Devonian first appearances Early Devonian extinctions {{Devonian-jawless-fish-stub