Unusual Stensiopelta Zenaspid Devonian Fish Fossil

Description: This is a fine example of a fish that has been termed a Cephalaspid, an Ostracoderm, and then an Osteostracan. This group is probably the most familiar of the Agnathans. They have a large horseshoe-shaped bony headshield with two round eye holes, a key-shaped nasal opening, and a tiny opening between the eyes that housed the pineal gland. The sides of the shield have an ornate appearance that was thought to have served a sensory function as did a similar area on the top of the head. In life it would have been covered with a mosaic of tiny platelets. This one displays a near-complete headshield, missing the distal end of the right cornual process. They evolved a number of quite exotic shield shapes from a simple semicircle to one with wideswept spines that encompassed the entire body. The Osteostracans went extinct at the end of the Devonian.

Also see: Paleozoic Fish Fossils