Ostracoderm

The term does not often appear in classifications today because it is paraphyletic (excluding jawed fishes and possibly the cyclostomes if anaspids are closer to them) and thus does not correspond to one evolutionary lineage.

[2] Ostracoderms had separate pharyngeal gill pouches along the side of the head, which were permanently open with no protective operculum.

Unlike invertebrates that use ciliated motion to move food, ostracoderms used their muscular pharynx to create a suction that pulled small and slow-moving prey into their mouths.

"[4] Neil Shubin writes: "Cut the bone of the [ostracoderm] skull open…pop it under a microscope and…you find virtually the same structure as in our teeth.

More recent research indicates that fish with jaws had far less to do with the extinction of the ostracoderms than previously assumed, as they coexisted without noticeable decline for about 30 million years.