''Astraspis'' ('star shield') is an extinct genus of primitive jawless fish from the Ordovician of Central

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

including the

Harding Sandstone The Harding Sandstone is a geologic formation in Colorado. It preserves fossils dating back to the Ordovician period. See also * List of fossiliferous stratigraphic units in Colorado This article contains a list of fossil-bearing stratigrap ...

of Colorado and Bighorn Mountains of Wyoming. It is also known from

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.Sacabambaspis janvieri. PY Gagnier - Vertébré ordovicien de Bolivie, 1993 It is related to other Ordovician fishes, such as the South American ''

Sacabambaspis ''Sacabambaspis'' is an extinct genus of jawless fish that lived in the Ordovician period. ''Sacabambaspis'' lived in shallow waters on the continental margins of Gondwana. It is the best known arandaspid with many specimens. It is related to '' ...

'', and the

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

n ''

Arandaspis ''Arandaspis prionotolepis'' is an extinct species of jawless fish that lived in the Ordovician period, about 480 to 470 million years ago. Its remains were found in the Stairway Sandstone near Alice Springs, Australia in 1959, but it was not ...

''.

Description

Nearly complete fossils suggest the living animals were about in length. The body had a mobile tail covered with small protective plate-like scales of less than and a forebody covered with plate-like scales larger than . The specimen from North America (described by Sansom et al., 1997) is to have had relatively large, laterally-positioned eyes and a series of eight gill openings on each side. The specimen was generally oval in cross-section. The protective bony plates covering the animal were composed of aspidin (chemically similar to modern shark's teeth), covered by tubercles composed of dentine.Sansom IJ, Smith MP, Smith MM and Turner P (1997
"''Astraspis'': The anatomy and histology of an Ordovician fish"
Palaeontology'', 40 (3): 625–642. It is from these tubercles (which are generally star-shaped) that the name 'Astraspis' (literally "star-shield") is derived.

References

Other sources

Michael J. Benton, ''Vertebrate Palaeontology'', 3rd edition, 2005

External links

* Palaeos
Pteraspidomorphi
Pteraspidomorphi genera Ordovician jawless fish Late Ordovician animals Ordovician fish of North America Prehistoric fish of South America Fossils of Bolivia Fossil taxa described in 1892 {{ordovician-animal-stub