How Long Have Sharks Been Shark-y? – #UREES270 – 2018

Coates, Finarelli, Sansom, Andreev, Criswell, Tietjen, Rivers, and La Riviere, 2018, An early chondrichthyan and the evolutionary assembly of a shark body plan: Proceedings of the Royal Society B, v. 285, 20172418

What’s it about?

This paper provides a new description of a 385-million-year-old fish called Gladbachus. This fish has characteristics of what we consider sharks and other characteristics that align it with placoderms and bony fishes. With this new description, the authors do a new cladistic analysis that shows what the primitive shark condition looked like and also shows that an enigmatic group called the Acathodii are likely along the same lineage as sharks.

Why does it matter?

As scientists, we wonder when certain characteristics of major groups of organisms arose. In the case of sharks, the arrangement of gill slits is unique, and with this new analysis, is one of the fundamental differences between the entire lineage leading to sharks and all other bony fish.

Why did I read this?

This is required reading for my vertebrate paleontology course this semester for the weekly unit on the classification and evolution of jawed fishes.