Scientists discover giant "swimming head" creature that lived 500 million years ago

Scientists have discovered a gigantic prehistoric relative of the horseshoe crab in the 500-million-year-old Burgess Shale in Canada, according to a study published in Royal Society Open Science on Wednesday. The creature is believed to have been one of the largest of its time, surpassing other previously discovered prehistoric crabs. 

Paleontologists at the Royal Ontario Museum named the new species Titanokorys gainesi and dated it to the Cambrian period — a part of an era between 541 and 485.4 million years ago that produced the most intense burst of evolution ever seen. While most ocean-dwelling organisms in the period were no larger than a pinky finger, the Titanokorys was over half a meter in length.

"The sheer size of this animal is absolutely mind-boggling, this is one of the biggest animals from the Cambrian period ever found," Jean-Bernard Caron, the museum's Richard M. Ivey curator of invertebrate paleontology and associate professor in ecology and evolutionary biology and Earth sciences at the University of Toronto, said in a press release.

Both the Titanokorys and the Anomalocaris were radiodonts, which were primitive arthropods with "multifaceted eyes, a pineapple slice-shaped, tooth-lined mouth, a pair of spiny claws below its head to capture prey and a body with a series of flaps for swimming," according to the press release. 

"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 added.

Some species of radiodonts also had large head carapace — or defensive shells — and Titanokorys has one of the largest ever found. Unfortunately, scientists have a poor understanding of why some radiodonts have "such a bewildering array" of carapace sizes and shapes, but Titanokorys's broad, flat head was probably designed to help it feed on the bottom of the ocean.

"The head is so long relative to the body that these animals are really little more than swimming heads," Joe Moysiuk, co-author of the study and a museum-based Ph.D. student in ecology and evolutionary biology at the University of Toronto, said in the statement.

The Burgess Shale, located in Canada's Kootenay National Park, was discovered less than 10 years ago. However, scientists have already found many smaller relatives of Titanokorys with similar shaped head carapaces in the area. According to the paleontologists, Titanokorys and its relatives may have competed for similar bottom-dwelling prey.