Rephrase the title:Ginormous worms ruled the Cambrian seas 500 million years back, fossils reveal

Imagine traveling back in time to Earth roughly 500 million years ago, right in the middle of the Cambrian Explosion. It would be like visiting an alien planet! The Blue Planet was in its “insecty invertebrate” phase, producing a vast array of the most unusual creatures imaginable.

Back then, complex life was just beginning to emerge, and scientists believed that primitive arthropod predators were at the top of the Cambrian food chain. However, a startling new discovery in Greenland has changed that perspective.

It turns out that a group of previously unknown giant worms called Timorebestia (which means “terror beasts” in Latin!) were the true rulers of the oceans 518 million years ago. These creatures were a remarkable 30 centimeters long, which was enormous in a world where most organisms were only a few inches in size. Picture them with fins and jaws, and you’ll have a good idea of these formidable Cambrian predators.

Dr Jakob Vinther, the lead researcher of the study, suggests that these Timorebestia might be distant relatives of our modern-day arrow worms. They’re much smaller than their Cambrian ancestors, but they share a common lineage. This means that these smaller predators might have held sway over the oceans before the arthropods rose to dominance.

In fact, the fossilised digestive systems of the Timorebestia reveal what they were eating for dinner. It turns out that a common swimming arthropod called Isoxys, which was covered in long, protective spines, was on the menu. Even with their armor, these creatures weren’t safe from the reign of the terror beasts.

The discovery of Timorebestia is just the beginning. The researchers have collected a wealth of exciting new fossils from the Sirius Passet region in North Greenland, promising further insights into the Cambrian world and its inhabitants.

The findings of this research have been published in Science Advances.