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

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including the Harding Sandstone of

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and Bighorn Mountains of

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. It is also known from

Bolivia , image_flag = Bandera de Bolivia (Estado).svg , flag_alt = Horizontal tricolor (red, yellow, and green from top to bottom) with the coat of arms of Bolivia in the center , flag_alt2 = 7 × 7 square p ...

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

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n ''

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

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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 The tail is the section at the rear end of certain kinds of animals’ bodies; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, r ...

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 A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

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 A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...

), 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