Taco-shaped arthropod fossils give new insights into the history of the first mandibulates

Fossils collected by ROM reveal Odaraia had mandibles. Paleontologists are finally able to place it as belonging to the mandibulates, ending its long enigmatic classification among the arthropods since it was first discovered in the Burgess Shale over 100 years ago and revealing more about and diversification.

The study "The Cambrian Odaraia alata and the colonization of nektonic suspension-feeding niches by early mandibulates

" was published in the journal Proceedings of the Royal Society B: Biological Sciences.

The study authors were able to identify a pair of large appendages with grasping jagged edges near its mouth, clearly indicative of mandibles, which are one of the key and distinctive features of the mandibulate group of animals.

This suggests that Odaraia was one of the earliest known members of this group. The researchers made another stunning discovery; a detailed analysis of its more than 30 pairs of legs, found an intricate system of small and large spines. According to the authors, these spines could intertwine, capturing smaller prey as though a fishing net, suggesting how some of these first mandibulates left the sea floor and explored the water column, setting the seeds for their future ecological success.

Researchers believe Odaraia could have swum upside down to gather food among its many spines along its legs. Credit: Illustrated by Danielle Dufault. Royal Ontario Museum

Photos of Odaraia fossil, ROMIP 60746. Credit: Jean-Bernard Caron, Royal Ontario Museum.

Fossil of Odaraia ROMIP 952413_1. Credit: Jean-Bernard Caron, Royal Ontario Museum