‘Little more than swimming heads’: new marine fossil discovered in Canada

A newly discovered fossil of an unusual marine animal has made waves in the science world. Found in the Canadian Rockies, the animal, though not bigger than half a metre, was huge compared to other marine animals living at the same time as it did, 500 million years ago.

The fossil, named Titanokorys gainesi, was introduced to the world in a study published on September 8, 2021 in the journal Royal Society Open Science.

The authors describe the specimen as “the largest Cambrian hurdiid [an extinct cosmopolitan family of radiodonts, a group of stem-group arthropods, which lived during the Paleozoic Era]  radiodont known so far, Titanokorys gainesi, gen. et sp. nov., from the Burgess Shale (Marble Canyon, Kootenay National Park, British Columbia).”

They add that “this new species bears a very large ovoid-shaped central carapace [a protective or defensive covering or shell] with distinct short posterolateral [posterior and lateral in position or direction] processes and an anterior [situated near or toward the head] spine.”

“The sheer size of this animal is absolutely mind-boggling, this is one of the biggest animals from the Cambrian period ever found,” says Jean-Bernard Caron, Royal Ontario Museum’s Richard M. Ivey Curator of Invertebrate Palaeontology, and one of the authors of the study, along with Joe Moysiuk.

"These enigmatic animals certainly had a big impact on Cambrian seafloor ecosystems. Their limbs at the front looked like multiple stacked rakes and would have been very efficient at bringing anything they captured in their tiny spines towards the mouth," Caron continues.

The Cambrian Period “is the first geological time period of the Paleozoic Era (the “time of ancient life”). This period lasted about 53 million years and marked a dramatic burst of evolutionary changes in life on Earth, known as the ‘Cambrian Explosion,’” according to Live Science.

The authors write that “This study is based on 12 Burgess Shale specimens of Titanokorys gainesi gen. et sp. nov ... All specimens are housed at the Royal Ontario Museum (ROM), Invertebrate Palaeontology section (ROMIP).”

The fossil derives its name from “Titans, a group of powerful Greek deities of great sizes, in reference to the large size of the central carapace element and from the Greek word Korys meaning helmet; gainesi, after Robert R. Gaines, Professor of Geology at Pomona College, who first joined the ROM-led field expeditions in 2008 as a research collaborator.” 

“Titanokorys is part of a subgroup of radiodonts, called hurdiids, characterized by an incredibly long head covered by a three-part carapace that took on myriad shapes. The head is so long relative to the body that these animals are really little more than swimming heads,” adds Joe Moysiuk, co-author of the study, and a ROM-based PhD student in Ecology & Evolutionary Biology at the University of Toronto.

According to the news release, it is not clear why some radiodonts evolved such a “bewildering” array of head carapace shapes and sizes; however “the broad flattened carapace form in Titanokorys suggests this species was adapted to life near the seafloor.”

“These enigmatic animals certainly had a big impact on Cambrian seafloor ecosystems. Their limbs at the front looked like multiple stacked rakes and would have been very efficient at bringing anything they captured in their tiny spines towards the mouth. The huge dorsal carapace might have functioned like a plough,” adds Caron, who is also an Associate Professor in Ecology & Evolutionary Biology and Earth Sciences at the University of Toronto, and Moysiuk’s PhD advisor.

According to the news release, the discovery of Titanokorys gainesi was profiled in the CBC’s The Nature of Things episode “First Animals.” These and other Burgess Shale specimens will be showcased in a new gallery at ROM, the Willner Madge Gallery, Dawn of Life, opening in December 2021.