The Cambrian Period, some 500 million years ago, hosted a bizarre array of life forms. Among them was Odaraia alata, a creature whose hard shell resembled a taco. New research reveals intriguing details about this extinct arthropod, suggesting it swam upside-down, used spiny legs to capture prey, and belonged to the mandibulate group – arthropods with jaws.
This fascinating creature resided in the Burgess Shale, a fossil-rich area in western North America that provides a glimpse into the Cambrian seafloor. The exceptional preservation of soft tissues in the Burgess Shale has allowed paleontologists to study Odaraia in remarkable detail. For this study, researchers analyzed roughly 150 Odaraia specimens, representing about half of all known examples.
“We weren’t the first to suspect Odaraia swam upside-down,” explains Alejandro Izquierdo-López, a paleontologist at the University of Toronto and lead author of the study published in Proceedings of the Royal Society B. “Our new findings, particularly concerning Odaraia’s spiny legs and their likely use in capturing food from the water column, strengthen this hypothesis.”
The Odaraia’s shell, while providing protection, wasn’t overly rigid. “We believe it possessed a texture somewhat similar to the shell of a shrimp or prawn you might find in a grocery store,” Izquierdo-López notes.
The Cambrian seas teemed with life unlike anything seen today. This period, known as the Cambrian Explosion (approximately 570 to 530 million years ago), witnessed an unprecedented diversification of life in the oceans. Odaraia, measuring about 8 inches (20 centimeters) in length, was just one of many unusual creatures inhabiting these ancient waters. Other Burgess Shale discoveries include the massive T. gainesi and a creature nicknamed the “Millennium Falcon” due to its resemblance to Han Solo’s iconic spaceship.
“The Burgess Shale is a paleontological goldmine,” states Jean-Bernard Caron, a paleontologist at the Royal Ontario Museum and co-author of the study. “Previous research on Burgess Shale fossils like Tokummia and Waptia has significantly advanced our understanding of early mandibulate evolution. However, certain species, like Odaraia, remained enigmatic until now.”
Beyond confirming Odaraia’s mandibles, the researchers meticulously examined the creature’s legs and spines. They propose that the spines played a crucial role in prey capture, facilitating the transition from bottom-feeding to exploiting food resources throughout the water column. This adaptation may have been a key development in the early evolution of mandibulates.
While the Burgess Shale continues to yield new discoveries, this study underscores the wealth of information yet to be gleaned from existing specimens. Further research promises to reveal even more about the remarkable diversity of Cambrian life and the evolutionary innovations that shaped the history of life on Earth.
