Ostracodermi
Also found in: Dictionary, Thesaurus, Medical, Wikipedia.
Ostracodermi
the oldest vertebrates. They are known from Silurian and Devonian deposits. The vertebrates measured up to 2 m long. They had an internal cartilaginous skeleton and an external shell made up of separate plates or small scales. Together with the extant Cyclostomata, the Ostracodermi belong to the Agnatha. They are significant in determining the stratigraphy of the Devonian.