Agnathan Cephalaspid Fish Fossils Death Assemblage

Zychaspis siemiradzkii

Osteostraci, Cornuata, Zenaspidida

Geological Time: Upper Devonian

Size: 110 mm in length, 115 mm across

Fossil Site: Usteczko, Podolia, Ukraine

Agnathan Fish FossilsDescription: This is a fine multiple 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 headshiled 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 shiled have an ornate appearance that was thought to have served a sensory function as did a similar area on the top of the head. A smaller example is preserved in ventral mode, and usually appears as this one as quite open. In life it would have been covered with a mosaic of tiny platelets. 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. This is a fine example of a fish death assemblage from the region.

Also see: Paleozoic Fish Fossils

click to enlarge fossil pictures

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