Giant ‘terror beast’ worms that colonised water 518 million years ago unearthed in Greenland

Fossils of giant predator worms dubbed “terror beasts” that colonised the water column more than 518 million years ago have been unearthed in North Greenland.

The large worms named Timorebestia, meaning “terror beasts” in Latin, were some of the earliest carnivorous animals to habit the planet, scientists from the University of Bristol in the UK say.

Growing to over 30cm in length, these worms with a distinct head, long antennae, massive jaws, and fins down the sides of their body, were some of the largest swimming animals during the Early Cambrian era over 520 million years ago.

“Timorebestia is a distant, but close, relative of living arrow worms, or chaetognaths. These are much smaller ocean predators today that feed on tiny zooplankton,” study senior author Jakob Vinther said.

The worms, which were giants of their day, would have been close to the top of the food chain, researchers say.

“That makes it equivalent in importance to some of the top carnivores in modern oceans, such as sharks and seals back in the Cambrian period,” Dr Vinther added.

The new findings suggest the ancient ocean ecosystems of the time were more complex than previously thought with a food chain that accommodated several tiers of predators.

In the fossil digestive systems of the unearthed worm, scientists found remains of a common, swimming arthropod of the time called Isoxys, suggesting that this animal group was their main food source.

Arthropods, a group of animals that includes insects, appear in the fossil record about 521 to 529 million years ago.

Other common old animal fossils from the Cambrian era include arrow worms that can be traced back at least 538 million years.

“Both arrow worms, and the more primitive Timorebestia, were swimming predators. We can therefore surmise that in all likelihood they were the predators that dominated the oceans before arthropods took off,” Dr Vinther explained.

The latest finding also sheds light on the origins of jawed predators of the ocean.

Scientists say more fossils from the expedition to be unveiled in the coming years will help unravel what the earliest animal ecosystems looked like and how they evolved.

“Over a series of expeditions to the very remote Sirius Passet in the furthest reaches of North Greenland, more than 82,5˚ north, we have collected a great diversity of exciting new organisms,” Tae Yoon Park, another senior author of the study from the Korean Polar Research Institute, said.

“Thanks to the remarkable, exceptional preservation in Sirius Passet, we can also reveal exciting anatomical details, including their digestive system, muscle anatomy, and nervous systems,” Dr Park added.