'Giant' predator worms more than half a billion years old discovered in North Greenland

In North Greenland, in the Early Cambrian Sirius Passet fossil location, fossils of a novel class of animal predators have been found. These massive worms might represent some of the first carnivorous creatures to have entered the water column over 518 million years ago, exposing an unknown predatory lineage from the past.

The Latin term for the new fossil creatures is Timorebestia, which translates to "terror beasts." Some of the biggest aquatic animals of the Early Cambrian era had features such as gigantic jaw structures within their mouths, a distinct head with long antennae, fins along the sides of their bodies, and a length of more than 30 cm.

"Prehistoric arthropods, like the weird-looking anomalocaridids, were the dominant predators during the Cambrian," said Dr. Jakob Vinther, a senior author of the study and member of the University of Bristol's Schools of Earth Sciences and Biological Sciences. On the other hand, Timorebestia is a near but distant relative of chaetognaths, or living arrow worms. These days, these ocean predators are substantially smaller and consume minuscule zooplankton."

"Our research shows that these ancient ocean ecosystems were fairly complex, with a food chain that allowed for several tiers of predators."

"Timorebestia would have been on the top of the food chain and were giants in their day. That puts its significance on par with that of some of the top predators found in today's waters, such sharks and seals, which existed throughout the Cambrian period."

The bones of a common swimming arthropod named Isoxys were discovered by the researchers inside the fossilized digestive tract of Timorebestia. "We can see these arthropods were a food source for many other animals," said Morten Lunde Nielsen, who is involved in the present work and was a former Bristol Ph.D. student.

The species was widespread at Sirius Passet and has long, forward- and backward-pointing defensive spines. They obviously weren't able to fully escape that destiny, though, since Timorebestia gobbled them up in large amounts."

Among the earliest Cambrian animal fossils are arrow worms. Arrow worms date back at least 538 million years, whereas arthropods first emerge in the fossil record between 521 and 529 million years ago.

"Arrow worms and the more primitive Timorebestia were both swimming predators," Dr. Vinther clarified. Therefore, we might assume that, before arthropods became popular, they were most likely the predators that ruled the waters. It is possible that their monarchy lasted for around 10–15 million years before they were surpassed by more prosperous populations."

Participating in the research, Luke Parry from Oxford University said, "Timorebestia is a really important discovery for understanding the origins of these jawed predators." Timorebestia possesses jaws within its head, but modern arrow worms have frightening bristles on the exterior of their heads for snaring prey."

"Microscopic jaw worms today exhibit characteristics similar to those of their ancestors over half a billion years ago—organisms that arrow worms shared." Timorebestia and similar fossils provide connections between closely related species that have extremely diverse appearances today."

The second senior author and head of the field mission, Tae Yoon Park of the Korean Polar Research Institute, continued, "Our discovery firms up how arrow worms evolved." A unique nerve area on the abdomen of living arrow worms is known as a ventral ganglion. It is exclusive to these creatures."

"We have discovered this preserved in Amiskwia, another fossil, and Timorebestia. Whether Amiskwia was closely linked to arrow worms as part of its evolutionary stem lineage has been a topic of contention. This theory has a lot more support now that these distinct ventral ganglia have been preserved."

"The discovery of such unusual predators in Sirius Passet excites us much. Through many journeys to the extremely isolated Sirius Passet, located at 82,5˚ north in North Greenland, we have gathered an impressive array of novel and fascinating species. We are also able to show fascinating anatomical characteristics, like as their nervous system, muscles, and digestive system, because to Sirius Passet's extraordinary preservation."

"We have many more exciting findings to share in the coming years that will help show how the earliest animal ecosystems looked like and evolved," Dr. Park said.