Today it was announced in the journal Nature that the mystery of Nectocaris pteryx, a problematic fossil species from the famous Burgess Shale deposits, has finally been solved. This tiny Invertebrate that lived in the Cambrian oceans 500 million years ago is, in fact, the oldest known cephalopod.
[UPDATE: The image I originally used in this post seems to have been removed from Wikipedia Commons. Follow this link to see before and after reconstructions.]
The original Nectocaris specimen was discovered 100 years ago, but it wasn’t formally described until 1976. However, the phylogenetic identity of the two inch long creature remained uncertain. It seemed to have similarities to both arthropods and chordates, but didn’t clearly fit into any known group. In this new report, researchers Martin Smith and Jean-Bernard Caron examined 91 additional specimens and came to the conclusion that N. pteryx is a mollusk, specifically a primitive, non-mineralized (i.e. shell-less) cephalopod. This revelation pushes the origins of cephalopods back at least 30 million years.
As we can see from the above reconstruction, Nectocaris resembled a modern cuttlefish. It had a flat “kite-shaped” body with large lateral fins, but only a single pair of long, grasping tentacles. It had a pair of non-faceted eyes on short stalks and a large anterior funnel, suggesting that cephalopod jet-propulsion evolved very early on. The lack of a shell disproves a long held assumption that shell-lessness is a relatively recent adaptation. It now seems that cephalopods didn’t evolve shells until much later, most likely “in response to increased levels of competition and predation in the Late Cambrian.”
Nature 465: 469-472 “Primitive soft-bodied cephalopds from the Cambrian”
