Anaspid Jawless Fossil Fish from Silurian Scotland
"Lasanius problematicus"

Lasanius problematicus

Phylum Chordata, Subphylum Vertebrata, Superclass Agnatha, Class Anaspida (Anaspidiformes)

Geological Time : Upper Silurian

Size: 47 mm in length

Fossil Site: Seggholm, Muikirk, Ayrshire, Scotland

Lasanius problematicus silurian fossil fishThe Anaspids were simple dorso-laterally compressed fish that probably led a bottom-dwelling existence. Their main common feature was a jawless Lasaniusmouth. Agnatha (from the Greek means, "no jaws") is a paraphyletic superclass of jawless fish in the phylum Chordata, subphylum Vertebrata. They were mostly quite small fishes that flourished during the Silurian 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 Lasanius. It had an elaborate array of dorsal scales that are seen here quite clearly. Complete examples of the Anaspida are quite rare.

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