The study, published in the journal Current Biology, examined 268 specimens collected in the 1980s and 1990s from a site in Yoho National Park in British Columbia and housed at the Royal Ontario Museum in Toronto. Dozens of these fossils contained the brain and nervous system of the half-billion-year-old Stanleycaris, which was part of an ancient, extinct offshoot of the arthropod evolutionary tree called Radiodonta, distantly related to modern insects and spiders. “It’s a once-in-a-lifetime discovery,” Joe Moysiuk, the study’s lead author and a doctoral candidate in ecology and evolutionary biology at the University of Toronto, said in an interview this week. “We’re getting so much information that we couldn’t get from the usual fossil record — things like brain features. We can see how many parts this animal’s brain is made of. We can see the processing centers for visual information that extend to its eyes animal, giving us all kinds of information about the neuroanatomy of this extinct organism. “This, in turn, helps us understand the evolution of the brain and nervous system of the group of modern animals we call arthropods, to include things today like insects and spiders.” Fossils show that the brain consists of two parts, which he said has deep roots in arthropod origins, and that its evolution probably preceded the three-part brain that characterizes today’s insects. “We think the third segment was added somewhere along this branch that is the tree of life between the divergence of the velvet worms and modern arthropods,” explained Moziuk. The researchers, he said, were able to trace how the evolution of parts of the brain occurred more than 500 million years ago. “It’s pretty incredible when you think we’re looking at these fossils. You think fossils are mostly things like shells and bones, not things like brains.” Moysiuk said the right conditions are needed to preserve the small, compressed fossils of an animal about 20 centimeters in size. “The organisms were preserved in these fast-flowing mudflats, so they were falling around and flattening in all kinds of orientations,” Moysiuk said, noting that most of the specimens were five centimeters or less. “So when we looked at the different fossils we find from these different preservation orientations, we’re able to piece together what the whole creature looked like in three dimensions.” The researchers found that Stanleycaris, known as a predator in the Cambrian period, had an unexpectedly large central eye at the front of its head in addition to its pair of eyelashes. “It highlights that these animals had an even stranger appearance than we thought, but it also shows us that early arthropods had already evolved a variety of complex visual systems like many of their modern relatives,” said Jean-Bernard Caron, supervisor and curator of Moysiuk. of Invertebrate Paleontology at the Royal Ontario Museum, said in a news release. “Since most radiotooths are known only from scattered pieces, this discovery is a critical leap forward in understanding what they looked like and how they lived.” Moysiuk said the find also shows the importance of fossil collections. “There are a lot of treasures you can find by trolling for things that have been discovered a long time ago,” he said. “We have this incredible collection of Burgess Shale fossils at the Royal Ontario Museum.” This report by The Canadian Press was first published on July 8, 2022.
