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-positionedeyes 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'steeth), 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.
References
^C. D. Walcott. 1892. Preliminary notes on the discovery of a vertebrate fauna in Silurian (Ordovician) strata. Geological Society of America Bulletin 3:153-172
^Sacabambaspis janvieri. PY Gagnier - Vertébré ordovicien de Bolivie, 1993