A newly discovered species of ancient arthropod has been found in the Marble Canyon site of the Canadian Burgess Shale fossil deposit. The species, which lived 508 million years ago, more than 250 million years before the arrival of the first dinosaurs, is believed to be a common ancestor to modern lobsters, spiders and butterflies.
The fossil, discovered by paleontologists from the University of Toronto (U of T), the Royal Ontario Museum and Pomona College in California is the first species to be described from the Marble Canyon site.
Named Yawunik kootenayi, the marine creature had two sets of eyes and grasping appendages similar to those of shrimps or modern beetles. Two of its three long claws had opposing rows of teeth to help the creature capture prey.
“This creature is expanding our perspective on the anatomy and predatory habits of the first arthropods, the group to which spiders and lobsters belong. It has the signature features of an arthropod with its external skeleton, segmented body and jointed appendages, but lacks certain advanced traits present in groups that survived until the present day. We say that it belongs to the ‘stem’ of arthropods.” said Cedric Aria in a statement.
Aria is a PhD candidate in U of T’s Department of Ecology & Evolutionary Biology and lead author of the resulting study published this week in Palaeontology.
According to the researchers, the creature’s name is a tribute to the Ktunaxa People who live in the Kootenay area where the Marble Canyon site was found. The name comes from a mythological marine monster.
The Yawunkik arable of moving its appendages backward and forward, retracting them beneath its body for swimming and spreading them wide when hunting. The animal also had “whip-like flagella” on the fronts of the claws, giving it extremely versatile appendages.
“Unlike insects or crustaceans, Yawunik did not possess additional appendages in the head that were specifically modified to process food. Evolution resulted here in a combination of adaptations onto the frontal-most appendage of this creature, maybe because such modifications were easier to acquire. We know that the larvae of certain crustaceans can use their antennae to both swim and gather food. But a large active predator such as a mantis shrimp has its sensory and grasping functions split up between appendages. Yawunik and its relatives tell us about the condition existing before such a division of tasks among parts of the organism took place,” said Aria.
Marble Canyon, thesite of the discovery, is 24 miles south of the Burgess Shale site in Yoho National Park in a particularly fossil rich part of British Columbia.
“Yawunik is the most abundant of the large new species of the Marble Canyon site, and so, as a predator, it held a key position in the food network and had an important impact on this past ecosystem. This animal is therefore important for the study of Marble Canyon, and shows how the site increases the significance of the Burgess Shale in understanding the dawn of animals,” said Jean-Bernard Caron, an associate professor at U of T’s Departments of Earth Sciences and Ecology & Evolutionary Biology and curator of invertebrate palaeontology at the ROM.
A short video with a graphic representation of the ancient predator can be seen on YouTube.
