The fossilized brain of the three-eyed creature dubbed Stanleycaris hirpex swam in Earth’s oceans 500 million years ago and its find could spark a rethink of the evolution of insects and spiders. The creature, described as ‘the stuff nightmares are made of’ because it looks like something out of a science fiction novel, had two eyes ‘on stalks’, with a third in the middle of its head, a formidable-looking circular mouth rimmed front teeth and claws with an impressive variety of spines. Quite an unusual specimen.
That’s fortunate, as researchers at the Royal Ontario Museum (ROM) in Toronto have announced that fossils of this strange, newly discovered animal are exceptionally complete, preserving a brain, nervous system, and a third eye.
Paleontologists found these ancient treasures in the Burgess Shale , a formation in British Columbia’s Canadian Rockies that is known for its abundant and well-preserved fossilized animal remains.
What was this creature like?
It is an oceanic predator that slithered through the deep sea like a stingray, scanning the murky water for its next prey, which it would seize with its spiny claws ready to catch anything that got too close. Stanleycaris would have been a nightmare for any little bottom dweller unlucky enough to cross his path. Its sophisticated sensory and nervous systems would have enabled it to efficiently select small prey in the dark.
According to experts, Stanleycaris hirpex is a 20-centimeter -long distant relative of today’s arthropods, the broad group that includes insects, spiders and crustaceans. The strange fossils offer evolutionary clues about how the brain, vision and body structure of arthropods became what they are today.
Unique features
Stanleycaris was a member of the radiodonts, apex predators that were some of the largest animals during the Cambrian period . In addition to its pair of stalking eyes, it possessed a large central eye at the front of its head, a feature never before seen in a radiodont.
“The details are really sharp and beautiful,” said Joseph Moysiuk, lead author, a doctoral candidate in ecology and evolutionary biology at the University of Toronto, Canada, and co-author of the paper published in the journal Current Biology . “You can see actual visual processing centers inside the eye stalks…almost unbelievable for something that’s half a billion years old.”
What scientists are most excited about is what’s inside the head of this strange creature. Remnants of the brain and nerves are still preserved after 506 million years in 84 of the fossils found. In modern arthropods, such as grasshoppers and other insects, the brain consists of three segments: protocerebrum, deutocerebrum, and tritocerebrum. But this creature has two.
A two-segmented head and brain have deep roots in the arthropod lineage, the authors say, and their evolution likely preceded the three-segmented brain that characterizes all living members of this diverse animal phylum.
“While fossilized brains from the Cambrian Period are not new, this discovery stands out for its amazing preservation quality and sheer number of specimens,” Moysiuk said. “We can even make out fine details, such as visual processing centers that serve the large eyes and nerve traces that enter the appendages. The details are so clear that it is as if we are looking at an animal that died yesterday .”
Finding fossilized soft tissue is rare. Most fossils are bones or hard body parts like teeth or exoskeletons, while brains and nerves are made of fatty substances that don’t normally survive.
Referencia: Joseph Moysiuk, A three-eyed radiodont with fossilized neuroanatomy informs the origin of the arthropod head and segmentation, Current Biology (2022). DOI: 10.1016/j.cub.2022.06.027. www.cell.com/current-biology/f … 0960-9822(22)00986-1
