An ancient sea predator with five eyes and a saw-mouth has a distant relative

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(ORDO NEWS) — Opabinia regalis, with five eyes, a backward-facing mouth, and a long, claw-tipped trunk, is one of the strangest celebrities of the Cambrian period.

In fact, this ancient marine life is so unique that scientists have never found another species in the fossil record that seems to fit into its family – but now the situation has changed.

Meet Utaurora comosa, a small, pointed-tailed marine animal that lived on Earth a few million years after Opabinia in what is now North America.

First described in 2008, U. comosa was originally classified as a relative of the fearsome Anomalocaris, a “claw-faced” predator that terrorized the Cambrian seas. But a new study suggests that U. comosa may have been much more than just another ancient predator.

In an article published in Proceedings of the Royal Society B , researchers reexamined the only known U. comosa fossil by comparing it to more than 50 living and extinct living specimens.

The team concluded that U. comosa is almost certainly related to Opabinia and not related to Anomalocaris, making U. comosa only the second member of the Opabinia family ever found in the world, and the first to be discovered in over 100 years.

From 541 million to 485 million years ago, the Earth’s seas first bloomed with biodiversity. This epoch, sometimes called the Cambrian explosion, was the very stage when relatives of all major groups of modern animals began to actively colonize the sea. The Cambrian Explosion also produced the world’s first truly fearsome apex predators.

These carnivorous killers are known as radiodonts, a name referring to the buzz-saw-shaped mouths on the underside of their heads. Many of them, including the infamous Anomalocaris, also had prehensile, claw-like appendages on the front of their heads, presumably for grabbing unsuspecting prey and shoving them straight into their mouths.

The only known fossil of U. comosa, found in the Cambrian Wheeler Formation in Utah, did not have such head appendages. Meanwhile, its inch-long body was divided into 14 or 15 furrows, each ending in a pointed flap, like that of Opabinia. Despite these details, the U. comosa fossil was classified as a radiodont in 2008.

This did not sit well with paleontologist Stephen Pates, a former Harvard graduate student and lead author of the new study. In their new paper, Pates and colleagues re-examined the U. comosa fossil by comparing the 125 features of the fossil to more than 50 groups of living and extinct arthropods, which are the largest phylum in the animal kingdom and include all insects, crustaceans and arachnids.

Analysis of the group showed that almost none of the traits of U. comosa corresponded to the radiodont family; rather, the fossil creature was almost certainly related to Opabinia. “This means that Opabinia was not as unique as we thought,” he said.


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