Vertebrate Zoology

Additional grouping of the subphylum Vertebrata:


Fossil Record of Vertebrate Animals

Jawless Ostracoderms (shell, skin)

Deepest vertebrate fossils are fragments of bony armor discovered in Ordovician rock [geological period corresponding to approx. 500 million to 425 million years before present (BP) in geological or atomic years based on radioisotope dating] in Russia and in the US.

The fossils represented organisms that were small, jawless forms collectively called ostracoderms (shell, skin).

The ostracoderms belong to the Agnatha superclass and consisted of three groups:

Jawed Placoderms (plate skin)

Deepest jawed vertebrate fossils are of two placoderm groups: