Of all the strange creatures unearthed from the Burgess Shale — a cache of remarkable Cambrian fossils deposited in the Canadian Rockies — none has been more fascinating than Opabinia. And for good reason – with five compound eyes and a trunk-like mouthpiece that ended in a claw, Opabinia seems otherworldly, like something imagined in a science fiction novel, rather than a swimmer in Earth’s oceans some 500 million years ago. past.
In “Wonderful Life,” his best-selling opus about the Burgess Shale, evolutionary biologist Stephen Jay Gould labeled Opabinia a “weird wonder,” saying it belonged to the pantheon of evolutionary icons such as Archeopteryx, Tyrannosaurus rex, and archaic human ancestors.
However, Opabinia is shrouded in evolutionary mystery due to a frustrating lack of fossils. Most of the Opabinia specimens were collected over a century ago, and the creature has never been found outside the Burgess Shale.
That’s why Stephen Pates, a paleontologist, was so stunned when he found a strange fossil stored in the Natural History Museum at Kansas University in 2017. At the time, Dr. Pates a graduate student who studied the diversity of radiodonts, Cambrian predators. that bore claw-like appendages. But the ghostly orange print in front of him lacked the distinctive appendages.
“When I first looked at it I wasn’t sure what it was, but I wasn’t sold that it was a radiodont,” says Dr. Pates, who is currently a researcher at the University of Cambridge.
The fossil had been unearthed in western Utah and had zigzagged body flaps and a tail brimming with spines to make a Stegosaurus jealous. Its features were reminiscent of Opabinia, but the creature’s ill-preserved head was little more than a crimson stain, obscuring its trunk and generous allotment of eyes.
To determine the identity of the Cambrian creature, Dr. Pates teamed up with several researchers from Harvard University, where he was a postdoctoral researcher, to put the fossil through a variety of phylogenetic tests. They compared 125 features of the fossil with more than 50 groups of modern and extinct arthropods and built detailed evolutionary trees.
According to Joanna Wolfe, a research associate at Harvard and co-author of the new study, the evolutionary trees allowed the team to rule out radiodonts and conclude that the new fossil was likely closely related to Opabinia, the lone wonder of the Burgess. shale.
In a paper published Wednesday in Proceedings of the Royal Society B, the team described the fossil as the second opabinoid ever discovered. They named the new species Utaurora comosa, after the Roman goddess of the dawn, Aurora, who turned her lover into a cicada – one of the countless arthropods that came after Utaurora.
Although the animal still looks weirder than arthropods, the researchers believe that Utaurora is an important precursor to the evolution of insects and crustaceans. Opabiniids were the first groups to have backward-facing mouths, and their fluted flaps appear to have been a precursor to segmentation, both common features of modern arthropods, according to Dr. pates.
However, it would not resemble an arthropod alive today. As it rippled through an ancient sea with its flaps and spiky tail fan, Utaurora probably waved its trunk to scoop food into its mouth. Opabinia were similar, although there were important differences between the two species. The younger Utaurora had more spines on its tail, and at just over an inch in length, its body was half the size of Opabinia’s.
The researchers believe the new discovery puts Opabinia into context, illustrating that one of the planet’s strangest creatures wasn’t just a one-hit wonder. “They were part of the bigger picture of what was going on and not just this weird curiosity,” said Dr. pates.
While Opabinia is no longer unique, the tiny sea creature is no less captivating to Dr. Wolfe, who grew up reading “Wonderful Life,” writes Gould’s captivating description of Opabinia as a catalyst for her paleontological career.
“I don’t think it’s such a weird miracle now, but I don’t think that makes it any less of a miracle,” she says. “It’s just not that weird.”