‘Giant’ predatory worms more than half a billion years old discovered in northern Greenland

Fossils of a new group of predatory animals have been located in the Lower Cambrian Sirius Passet fossil locality in northern Greenland. These large worms may be among the first carnivorous animals to colonize the water column more than 518 million years ago, revealing a past dynasty of predators that scientists never knew existed.

The new fossil animals have been named Timorebestia, meaning “terrorist beasts” in Latin. Adorned with fins on the sides of their bodies, a distinct head with long antennae, massive jaw structures inside their mouth, and measuring over 12 inches long, they were among the largest swimming animals in the world. beginning of the Cambrian.

“We previously knew that primitive arthropods were the dominant predators in the Cambrian, such as the bizarre-looking anomalocarids,” said author Dr Jakob Vinther from the Schools of Earth and Biological Sciences at the University of Bristol. principal of the study. “However, Timorebestia is a distant, but close, relative of the living arrow worms, or chaetognaths. They are much smaller oceanic predators today that feed on tiny zooplankton.”

“Our research shows that these ancient ocean ecosystems were quite complex, with a food chain that allowed for multiple levels of predators to exist.”

“Timorebestia were giants of their time and would have been near the top of the food chain. This makes it equivalent in importance to some of the major carnivores of modern oceans, such as sharks and seals of the Cambrian period.”

Inside the fossilized digestive system of Timorebestia, researchers found the remains of a common swimming arthropod called Isoxys. “We can see that these arthropods were a food source for many other animals,” said Morten Lunde Nielsen, a former doctoral student. student at Bristol and part of the current study.

“They are very common in Sirius Passet and had long protective spines, pointing both forward and backward. However, they clearly did not completely manage to avoid this fate, as Timorebestia was munching on them in large quantities. quantity.”

Arrow worms are one of the oldest animal fossils from the Cambrian. While arthropods appear in the fossil record around 521 to 529 million years ago, arrow worms can be traced back to at least 538 million years ago.

Dr Vinther explained: “Arrow worms, along with the more primitive Timorebestia, were swimming predators. We can therefore assume that these were in all likelihood the predators that dominated the oceans before the arthropods took off. Perhaps they had a dynasty of around 10–15 million years before they were replaced by other, more successful groups. »

Luke Parry from the University of Oxford, who participated in the study, added: “Timorebestia is a very important discovery for understanding where these jawed predators came from. Today, arrow worms have menacing bristles on the outside of their heads to catch prey, while Timorebestia has jaws on the inside of their heads.

“This is what we see today in microscopic jaw worms – organisms with which arrow worms shared an ancestor more than half a billion years ago. Timorebestia and other similar fossils establish connections between closely related organisms that appear very different today.”

“Our discovery confirms the evolution of arrow worms,” ​​added Tae Yoon Park of the Korea Polar Research Institute, the other lead author and leader of the field expedition. “Living arrow worms have a distinct nerve center on their bellies, called the ventral ganglion. It is completely unique to these animals.”

“We found it preserved in Timorebestia and another fossil called Amiskwia. People have debated whether or not Amiskwia was closely related to arrow worms as part of their evolutionary lineage. The preservation of these unique ventral ganglia gives us a lot no more confidence in this hypothesis.”

“We are very pleased to have discovered such unique predators at Sirius Passet. During a series of expeditions to the very isolated Sirius Passet region on the edge of northern Greenland, at over 82.5° north, we collected a great diversity of exciting animals.” New organisms. Thanks to the remarkable and exceptional preservation of Sirius Passet, we can also reveal exciting anatomical details, including their digestive system, muscular anatomy and nervous system. “

“We have many more exciting discoveries to share in the years to come that will help show what early animal ecosystems looked like and evolved,” concluded Dr. Park.

The work is published in the journal Scientists progress.