Astraspis

Astraspis ('star shield') is an extinct genus of primitive jawless fish from the Ordovician of Central North America and Bolivia (Gagnier, 1993). It is related to other Ordovician fishes, such as the South American Sacabambaspis, and the Australian Arandaspis.

Basic anatomy
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.[1] It is from these tubercles (which are generally star-shaped) that the name 'Astraspis' (literally "star-shield") is derived

In popular culture
It has a small cameo in the 2003 BBC series Sea Monsters: A Walking with Dinosaurs Trilogy, a spin-off to the famed Walking with Dinosaurs, where Nigel Marven uses a dead Astraspis as bait to attract a sea scorpion. The creature is identified in the series' novelisation. It is also said to be an armour-plated fish in the documentary, whereas is more closely related to the modern lamprey. Astraspis was also featured in Animal Armageddon.