With five eyes, a backward-facing mouth and a long proboscis with claws instead of a nose, Opabinia regalis is one of the strangest species of the Cambrian period. In fact, this ancient marine animal is so unique that scientists have never discovered another species that seems to belong to the same family. And this, until today.
Indeed, you will discover through this article Utaurora comosa, a spiny-tailed marine species that lived a few million years after Opabinia regalis, in what is now North America. First described in 2008, Utaurora comosa was originally classified as a relative of the fearsome Anomalocaris, a claw-headed apex predator that terrorized the Cambrian oceans. But a new study suggests that Utaurora comosa may have been much more than another ancient predator.
In a paper published Feb. 9 in the scientific journal Proceedings of the Royal Society B, researchers re-examined the species’ only known fossil by comparing it to more than 50 specimens of living and extinct animals. The team concluded with near certainty that it is a relative of Opabinia regalis, not a relative of Anomalocaris, making Utaurora comosa only the second member of the Opabinia regalis family ever discovered and the first in over 100 years. “The strangest Cambrian wonder is no longer alone,” reads the study report written by the researchers.
Between 541 million and 485 million years ago, the world’s seas experienced high biodiversity for the first time. It was during this time, sometimes referred to as the Cambrian Explosion, that the ancestors of all major groups of animals alive today appeared in the water. The Cambrian Explosion also gave rise to the first particularly fearsome predators. These carnivorous killers are known as “radiodonts,” after the circular saw-like mouth on the underside of their heads. Many of them, including the infamous Anomalocaris, also had clawed appendages on the front of their heads, presumably to catch unsuspecting prey and bring them to the entrance of their mouths.
The only known fossil of Utaurora comosa, found in the Wheeler Cambrian Formation in Utah, had no such appendages on its head. Instead, its body, a few centimeters long, was segmented into 14 or 15 grooves, each ending in a pointed flap, much like Opabinia regalis. Despite these details, the fossil of the species was classified as radiodont in 2008.
The discovery of a historic animal
But after much research, that didn’t sit well with paleontologist Stephen Pates, former Harvard graduate student and lead author of the new study. So in the new scientific paper published a few days ago, Stephen Pates and his colleagues re-examined the Utaurora comosa fossil, comparing 125 of its features to more than 50 groups of living and extinct arthropods, which make up the largest phylum (the second level of classical classification of living species) in the animal kingdom and include all insects, crustaceans and arachnids.
And finally, the team’s analysis showed that almost none of the species’ traits matched the radiodont family. Instead, the fossil creature was definitely related to Opabinia regalis. “This means that Opabinia regalis was not the only opabiniid. It was therefore not as unique a species as we thought at the time,” explained Stephen Pates in a statement.