This 500-Million-Year-Old 'Swimming Head' Fossil Once Swam the World's Oceans

The ancient sea-dweller used a pair of spiny claws like "multiple stacked rakes" to capture prey.

Published Sep 8, 2021

 ( Jean-Bernard Caron, © Royal Ontario Museum)
Image Via Jean-Bernard Caron, © Royal Ontario Museum

A newly described deep-sea dweller that swam the world’s oceans 500 million years ago is bridging a “morphological gap” in ancient ocean species, lending a new understanding to the ecological worlds of Earth’s past.

At least a dozen individuals of the now-named Titanokorys gainesi were found in a group of half-a-billion-year-old rocks in Kootenay National Park in the Canadian Rockies. Nicknamed a giant “swimming head,” Titanokorys measured nearly 1.5-feet long — a giant compared to most marine animals at the time from the Cambrian period. (Most were smaller than the size of a human pinky finger.)

“The sheer size of this animal is absolutely mind-boggling, this is one of the biggest animals from the Cambrian period ever found,” said paleontologist and study author Jean-Bernard Caron in a news release.

Titanokorys were primitive arthropods, ancestors of modern crustaceans, that belonged to a large and diverse group of widespread, stem-like animals known as radiodonts. With multifaceted eyes and a mouth lined with teeth, Titanokorys used a pair of spiny claws like “multiple stacked rakes” to capture prey and propelled itself through the water using flaps along its pineapple-shaped body.

View of Titanokorys gainesi from the front. Illustration by Lars Fields, © Royal Ontario Museum

But what sets the creature apart from other related arthropods of its time is a uniquely long head carapace, an exoskeleton like those seen in turtles, that may have functioned like a plow to harvest food from the seabed.

“The head is so long relative to the body that these animals are really little more than swimming heads,” added Joe Moysiuk, co-author of the study.

Titanokorys fossils occur in the same fossil bedding as the closely related Cambroraster. Both species have similar morphologies that could suggest the two may be different sexes of the same species.

To describe the creature, scientists from Royal Ontario Museum (ROM) in Canada analyzed 12 specimens collected a decade ago from British Columbia’s Burgess Shale, a region rich in fossils that is now listed as part of the UNESCO World Heritage site. Each specimen was photographed and traced in Adobe Photoshop CS5 before being compared against other previously described radiodont species like Cambroraster.

The broad, flattened carapace of Titanokorys suggests that it was adapted for a life near the seafloor. This leads to a more likely explanation for the differences between the two species: a concept known as “selective resource exploitation” by which one animal has evolved specially adapted techniques that allow it to predate on organisms not hunted by competitors. It is thought that two co-existed in separate, but sometimes overlapping, ranges with Titanokorys eating larger prey.  

“Regardless of the exact ecological interactions between these species, this study strengthens recognition of the Cambrian benthos as a rich habitat for an array of large predatory animals to exploit,” concluded the study authors in the peer-reviewed journal Royal Society Open Science.

A close-up photograph of Titanokorys gainesi carapace. Jean-Bernard Caron, © Royal Ontario Museum


Caron, J. B., and J. Moysiuk. “A Giant Nektobenthic Radiodont from the Burgess Shale and the Significance of Hurdiid Carapace Diversity.” Royal Society Open Science, vol. 8, no. 9, p. 210664. (Atypon),

CNN, Ashley Strickland. “Giant ‘swimming Head’ Creature Lived in Our Oceans 500 Million Years Ago.” CNN, Accessed 8 Sept. 2021.

“Is This ‘Pink Fairy Armadillo’ Real?” Snopes.Com, Accessed 8 Sept. 2021.

“Massive New Animal Species Discovered in Half-Billion-Year-Old Burgess Shale.” EurekAlert!, Accessed 8 Sept. 2021.

Madison Dapcevich is a freelance contributor for Snopes.