Researchers at the University of Toronto have finally classified a 500 million year old squid-like carnivore known as Nectocaris pteryx, a discovery three decades in the making.
PhD student Martin Smith and curator Jean-Bernard Caron of U of T’s Department of Ecology and Evolutionary Biology and the Department of Natural History at the ROM made the discovery, which was recently published in Nature. Smith explains, “We think that this extremely rare creature is an early ancestor of squids, octopuses, and other cephalopods.”
The discovery was made possible by fossils collected by the ROM from the famous Burgess Shale site in the UNESCO World Heritage Canadian Rocky Mountain Parks in British Columbia over the past 30 years. Previously, all knowledge of Nectocaris came from a lone specimen described in 1976, whose ambiguous characteristics made Nectocaris impossible to classify until now.
The study reveals that Nectocaris is similar to known members of the modern cephalopod group, which includes squid, octopus, cuttlefish, and nautilus, as well as common fossils such as the now-extinct ammonites and belemnites.
“This is significant because it means that primitive cephalopods were around much earlier than we thought, and offers a reinterpretation of the long-held origins of this important group of marine animals,” says Smith. “We know very little about the relationships between the major groups of mollusks, and the early history of the group. Fossils like Nectocaris help us map out how the groups alive today might be related, and how they evolved. This tells us something about how biodiversity originated in the past, and helps us to understand the rich tapestry of life today.”
The study required examining nearly 100 fossils to reconstruct and visualize three-dimensionally the prehistoric Nectocaris, a procedure involving technical drawings and mapping out the contrasting dark and light features of the fossils.
The specimens collected from the Burgess Shale site reveal that Nectocaris was kite-shaped and flattened from top to bottom, with large stalked eyes and a long pair of grasping tentacles, which the researchers believe helped it hunt for and consume prey. The creature probably swam using its larger lateral fins and its nozzle-like funnel to accelerate by jet propulsion.
The findings mean that cephalopods originated 30 million years earlier than previously thought, much closer to the first appearance of complex animals in the Cambrian explosion, which Smith explains as “an explosion of biodiversity in living organisms about 500 million years ago.”
This is of particular significance since it was previously thought that cephalopods evolved in the Late Cambrian period, when gradual modifications to the shells of creeping, snail-like animals made them able to float. The classification of Nectocaris reveals that the first cephalopods actually started swimming without the aid of gas-filled shells, and that shells evolved much later, most likely in response to increased levels of competition and predation in the Late Cambrian period.
“We go from simple pre-Cambrian life-forms to something as complex as a cephalopod in the geological blink of an eye, which illustrates just how quickly evolution can produce complexity.”
Smith, who studied chemistry at Cambridge and whose work now focuses on convergent evolution agrees there are still surprises to be found in the fossil record. “Fossils can only ever tell us a part of the story. Exceptional soft-bodied fossils like Nectocaris, combined with advances in developmental and molecular biology, still have a lot to bring to the table, and I’m sure that they will continue to help us refine and replace our current hypotheses.”
