Astraspis

Astraspis Temporal range: 467–443 Ma PreꞒ Ꞓ O S D C P T J K Pg N middle-late Ordovician
Fossil specimen of A. desiderata, Field Museum of Natural History
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Infraphylum:	Agnatha
Class:	†Pteraspidomorphi
Subclass:	†Heterostraci
Order:	†Pteraspidiformes
Genus:	†Astraspis Walcott, 1892[1]
Type species
Astraspis desiderata Walcott 1892
Synonyms
†Pycnaspis splendens Ørvig 1958 †Astraspis splendens (Ørvig 1958) Smith, Sansom & Smith 1995

Astraspis ('star shield') is an extinct, monotypic genus of primitive jawless fish from the Ordovician of Central North America including the Harding Sandstone of Colorado and Bighorn Mountains of Wyoming. It is also known from Bolivia.^[2] It is related to other Ordovician fishes, such as the South American Sacabambaspis, and the Australian Arandaspis.

Nearly complete fossils suggest the living animals were about 200 mm (7.9 in) in length. The body had a mobile tail covered with small protective plate-like scales of less than 1 mm (0.039 in) and a forebody covered with plate-like scales larger than 2 mm (0.079 in). 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.^[3] It is from these tubercles (which are generally star-shaped) that the name 'Astraspis' (literally "star-shield") is derived.

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

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