The Anaspids were simple dorso-laterally compressed fish that probably led a bottom-dwelling existence. Their main common feature was a jawless mouth. Indeed the name means without jaws. They were mostly quite small fishes that flourished during the Silurain and Devonian that then became extinct except for their modern day relatives the Lampreys and Hagfishes. The gills opened as a row of holes along the side of the animal, typically numbering from 6-15. One unusual example from Canada holds the record for gills at 30 pairs! They probably behaved much like the lampreys, and most lived in freshwater environments. This fine example is known as Birkenia. It had an elaborate array of dorsal scales, some of which are seen here. Indeed, these alone would be sufficient to identify this specimen.