Tremataspis mammillata Primitive Silurian Jawless Fish

The Osteostracii are a primitive group of jawless fish. This one is known as Tremataspis and comes from the Silurian of Estonia. It had a rounded shield that covered most of the body and was presumed to have aided the fish in plowing through the substrate in search of food. Notice the centrally-located eye holes, single nostril , sensory fields and ornamentation. The shield was one solid piece, and as such most likely did not grow as the animal aged. Presumably the larvae had no such protection, growing a shield only once they had reached the mature stage. This one shows both the dorsal and ventral sides. While the dorsal side is essentially complete, the ventral side preserves some 65% of the original shell.