Description: 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. See my other offerings for an example of the congeneric Tremataspis mammillata.

Also see: Paleozoic Fish Fossils