What had spiky claws sticking out of its mouth, a body shaped like a toilet brush, and looked like it’d slipped off the cover of a sci-fi novel? A Cambrian-era ocean predator known as Stanleycaris hirpex. Newly found fossils of the bizarre creature are exceptionally complete, preserving the brain, nervous system and a third eye.
Researchers at the Royal Ontario Museum (ROM) in Toronto recently announced the discovery of fossils of this strange animal as part of an “amazing” trove of fossils dating back 506 million years, according to a expression (opens in new tab).
Paleontologists found these ancient treasures in the Burgess Shale, a formation in British Columbia’s Canadian Rockies known for its numerous and well-preserved fossil animal remains, and among the half-billion-year-old fossils were numerous specimens of the marine predator S.hirpex.
“What makes this find so remarkable is that we have dozens of specimens that show the remains of the brain and other elements of the nervous system, and they’re incredibly well preserved and show really fine detail,” said Joseph Moysiuk, lead author of a study , who describes the fossils, and a University of Toronto graduate student in ecology and evolutionary biology.
“Before that, there had been few other finds of fossilized brains, particularly from the Cambrian period, but this is still quite rare and has only been observed in the last 10 years or so,” Moysiuk told Live Science. “Of most of the species we’ve seen with fossilized brains, only one or two specimens are available.”
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Despite being small – less than 20 centimeters long – S.hirpex was probably an imposing sight for its even smaller prey.
“It had this really ferocious contraption of spiky claws and a round mouth that made it look absolutely ferocious,” Moysiuk said. “It also had long, rake-like spines to scour the seabed to look for buried organisms, side flaps to help it slide through the water, and trident-shaped spines attached to the opposite appendage, which we believe that it was used to jut out a jaw to crush its prey.”
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The fossils show that the brain of S.hirpex was divided into two segments: the protocerebrum, connected to its eyes, and the deuterocerebrum, connected to the frontal claws. This brain structure differs from the three-lobed structure of modern arthropods that are distant relatives of S. hirpex, such as B. Insects. In contrast, the brains of these modern relatives consist of a protocerebrum, a deutocerebrum, and a tritocerebrum, which connects the brain to the labrum, or upper lip, of an insect, among other things.
“The preservation of the brains of these animals gives us a direct look at the evolution of the nervous system from the perspective of the fossil record,” Moysiuk said.
Radiodonta, an extinct offshoot of the arthropod evolutionary tree that includes Stanleycaris“is an important group to be aware of as it gives us a better understanding of the evolution of modern arthropods,” Moysiuk said.
Another interesting aspect of S.hirpex was its oversized middle third eye, a feature first observed in a radiodont. While the study’s authors aren’t sure how ancient arthropods used this eye, it may have helped the animal track down its prey, Moysiuk suggested.
“Discovering the third eye was quite a shock to us because we started to think we had a pretty good understanding of radiodonts and what they looked like,” he said. “For the first time we were able to recognize this gigantic central eye in radidonts in addition to the pair of stick eyes that we are already familiar with.”
Although some modern arthropods, such as dragonflies and wasps, also have medium eyes, they are usually more sensitive than the other two eyes and still cannot focus as well. “We can only speculate, but we think this third eye helped in an animal’s orientation, and it’s particularly important for a predator like Stanleycaris that has to move quickly and precisely around the environment,” said Moysiuk.
three of the S.hirpex Fossils unearthed during the excavation are now on permanent display at the Royal Ontario Museum in its Willner Madge Gallery, Dawn of Life.
The results were published in the journal on July 8 Current Biology (opens in new tab).
Originally published on Live Science.