Athena Review Image Archive ™
Astraspis desiderata
Astraspis desiderata (after Samson et al. 1997)
Astraspis desiderata is an early, armored fish from the Ordovician period, dating from about 450 mya.The name Astraspis means "star shield," deriving from astr- "star," and -aspis "shield" [Gk]. It belongs to the phylum Chordata, the class Pteraspida, and the subclass Astraspida.
Fossils of the taxa were discovered in both Colorado (Sanson et al 1997) and Bolivia (Gagnier 1993). Astraspis is related to Sacabambaspis from Bolivia, with possible differences in the tail structure. The body length is about 20 cm (8 in)
The Colorado specimen of Astraspis desiderata (see figure) had relatively large eyes flanked by a series of eight gill openings on each side. The head region was covered with small bony less greater than 2 mm in size, and a mobile tail covered with plates over 1 mm long. These protective plates were composed of aspidin (like that in sharks' teeth), covered by dentine tubercles.
Both
Astraspis and Sacabambaspis show clear evidence of a sensory structure
called a lateral line system, which allows the fish to detect the
direction and distance of movements in the water.
Reference:
Sansom, I.J.; Smith, M.P.; Smith, M.M. and Turner, P. 1997; Astraspis: The anatomy and histology of an Ordovician fish Palaeontology; 40 (3): 625–642. .
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