Michael Coates, professor of organismal biology and anatomy, published a study in Nature recently that sheds light on the early evolutionary history of vertebrates. Mike and his colleagues performed CT scans of the fossilized skull of a 280-million-year-old, shark-like fish found in the Karoo sediments of South Africa. The fossil was thought to belong to an early type of shark, but the scans revealed that the interior of the skull showed telltale structures of modern day chimaeras, an odd, deep water-dwelling group of cartilaginous fish related to sharks.
Chimaeras have long fascinated biologists because their bodies include features of sharks, ray-finned fishes and tetrapods. Modern day chimaeras have extremely slow-evolving genomes as well, and seem to offer the best promise of finding an archive of information about conditions close to the last common ancestor of humans and a Great White. But their odd anatomy and relative scarcity of intact fossils have made it difficult to place them on the evolutionary tree. Thanks to innovative use of modern technology by Mike and his team, we now have a better understanding of our shared past with these fascinating creatures.