Joint ROM and U of T research team classifies ancient species as related to modern cephalopods including squids and octopuses
A study by researchers at the Royal Ontario Museum (ROM) and the University of Toronto (U of T) sheds new light on a previously unclassifiable 500 million-year-old carnivore known as Nectocaris pteryx. The positive identification was made after examining specimens from the ROM’s Burgess Shale collection, the world’s largest collection of creatures from this Middle Cambrian (over 500 million years old) locality. Nectocaris is now believed to be one of the oldest and most primitive cephalopods, a class of molluscs that includes modern squids, octopuses and cuttlefish.
These findings, co-authored by Dr. Jean-Bernard Caron, ROM Associate Curator of Invertebrate Palaeontology, and Martin Smith, a PhD student in U of T’s Department of Ecology and Evolutionary Biology, are presented in a paper titled Primitive soft-bodied cephalopods from the Cambrian, to be published May 27, 2010 in the scientific journal Nature. A podcast about Nectocaris pteryx and the significance of these new findings can be viewed on the ROM’s website.
“Our discovery allows us to push back the origin of cephalopods by at least 30 million years, to the famous Cambrian explosion about a half-billion years ago,” said Caron. “Soft-tissues of cephalopods tend to decay quickly, so it was difficult to know what primitive cephalopods looked like. The Burgess Shale is well known for its exceptional preservation of soft-bodied animals. Now, thanks to our reinterpretation of Nectocaris, the ROM’s collection from this important locality provides a fascinating snapshot into the early evolution of this group.”
The new interpretation became possible with the discovery of 91 new fossils that were collected by the ROM from the famous Burgess Shale site over the past three decades. Nectocaris was formerly known from a single, poorly preserved soft-bodied fossil collected in the early 20th century and not described until 1976. However, this single specimen did not allow a precise analysis of the morphology and ecology of this species, and its affinities remained ambiguous. The recent specimens were collected by now-retired ROM Curator Desmond Collins, mainly from a new Burgess Shale locality he discovered in 1984 just above the Walcott Quarry.
The new specimens, between two and five centimetres long, show that Nectocaris was kite-shaped and flattened from top to bottom, with large, stalked eyes and a long pair of grasping tentacles, which Smith and Caron believe helped it to hunt for and consume prey. The researchers further suggest that the creature swam using its large lateral fins, and, like modern cephalopods, probably used its nozzle-like funnel to accelerate by jet propulsion. It also contained a large pair of gills that appear in some fossils to be choked with mud, suggesting that the animals were fossilized after being caught in an underwater mud-flow.
Particularly surprising was the lack of a mineralized shell in Nectocaris. It was formerly believed that the most primitive ancestor of this group was a simple shelled creature similar to the modern nautilus or the now-extinct ammonite. Smith explains: “It’s long been thought that cephalopods evolved in the Late Cambrian period, when gradual modifications to the shells of creeping, snail-like animals made them to able to float. Nectocaris shows us that the first cephalopods actually started swimming without the aid of gas-filled shells. Shells evolved much later, probably in response to increased levels of competition and predation in the Late Cambrian.”
Unexpectedly, the new material from the Burgess shale led the authors to reinterpret other enigmatic Cambrian soft-bodied fossils from the Emu Bay Shale in Australia and the Chengjiang biota in China (Vetustovermis and Petalilium) as members of the same family of organisms. “The Chinese site is about 10 million years older than the Burgess Shale, and demonstrates that the origin of this group can be traced even further back in time, probably to the onset of the Cambrian explosion. Finding similar forms in distant sites also demonstrates that primitive cephalopods had already evolved in world oceans by the Middle Cambrian and were part of normal marine ecosystems during that period,” said Caron.
The Burgess Shale is located in Yoho National Park, within the UNESCO World Heritage Canadian Rocky Mountain Parks, near the town of Field, British Columbia. The spot contains some of the world’s most spectacularly preserved fossilized remains of soft-bodied organisms that evolved in the Cambrian Period, 500 million years ago. Not only has this site provided numerous specimens of Nectocaris, but also tens of thousands of other organisms belonging to at least 200 species, many of them the most primitive members of animal groups that are still known today. Concealed within layers of rock are fine details of their anatomy, allowing a greater understanding of the ecology, diversity and evolution of animal communities during that period.
The ROM is a major contributor to the study of the Burgess Shale and the fascinating creatures found therein. The Museum has led dozens of field explorations and excavations since 1975, and now holds the world’s largest collection of Burgess Shale specimens, over 150,000 in total. Today, ROM curator Dr. Jean-Bernard Caron continues to lead field expeditions and to conduct research on Burgess Shale fossils with his students. Highlights from the ROM’s extensive Burgess Shale collections will be on permanent display in the future Peter F. Bronfman Gallery of Early Life and on the Virtual Museum of Canada Burgess Shale website to be launched in the spring of 2011, a collaboration between the ROM and Parks Canada.
The new research involving Nectocaris was partially funded by a Natural Sciences and Engineering Research Council of Canada Discovery Grant awarded to Caron and U of T fellowships to Smith.
Visit the links below to learn more the ROM's Burgess Shale collection and ongoing research: