A species of predatory worm over 500 million years old has been discovered in Greenland

A reconstruction of the pelagic ecosystem and fossilized organisms at Sirius Passet, revealing how the worm was one of the largest predators more than 518 million years ago (Work by Bob Nicholls – University of Bristol)

The Ediacaran-Cambrian transition (about 540 million years ago) was marked by an exceptionally large expansion in animal diversity and disparity, which coincided with the exploration of new regions through deeper and more varied excavation strategies and the colonization of strata of water. The diversification of animals during the Ediacaran-Cambrian transition is increasingly recognized as a two- or three-phase change in diversity: first in the Late Ediacaran “Worm World,” followed by a subsequent expansion during the Early Cambrian (Earthenuvian) that eventually it expanded markedly in diversity during the Cambrian age.

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In line with this knowledge, work has been published in the journal Science Advances reporting that fossils of a new group of predatory animals have been located in the Lower Cambrian locality of Sirius Passet, in northern Greenland. These large worms may have been some of the first carnivorous animals to colonize the water column more than 518 million years ago, revealing an ancient dynasty of predators that scientists never knew existed.

The new fossils were named Timorebestia, which means “terrorist beasts” in Latin. Featuring fins on the sides of the body, a distinctive head with long antennae, huge jaws inside the mouth and a length of over 30cm, these were some of the largest swimming animals of the Early Cambrian.

Fossil of Timorebestia koprii, the largest known specimen, almost 30 cm long (photo: Dr. Jakob Vinther)

It was already known that primitive arthropods were the dominant predators during the Cambrian, such as the strange-looking anomalocarids. However, the Fearbeast is a distant, yet close, relative of the living arrowworms or chaetognaths. Today these are much smaller ocean predators that feed on tiny zooplankton. Research shows that these ancient ocean ecosystems were quite complex, with a food chain that allowed for varying levels of predators.

The Timorese Beasts were giants of their time and would have been near the top of the food chain. This makes them equivalent in importance to some of the major carnivores of the modern oceans, such as sharks and seals, but dating back to the Cambrian period. Inside Timorebeast’s fossilized digestive system, researchers found remains of a common swimming arthropod called Isoxys, which was a food source for many other animals. They are very common on Sirius Passet and had long protective spines that pointed both forwards and backwards. However, they clearly couldn’t avoid that fate, because he chewed them up in large quantities.

Arrow worms are one of the oldest animal fossils from the Cambrian. While arthropods appear in the fossil record between 521 and 529 million years ago, the earliest arthropods date back at least 538 million years.

Doctor Jakob Vinther in the city of Sirius Passet in 2017 shows the largest specimen of Fearbeast after its discovery (EFE/ Jakob Vinther)

Both arrow worms and the more primitive Timorebeasts were swimming predators. Therefore, the researchers indicate that it is possible to assume that, in all likelihood, they were the predators that dominated the oceans before arthropods took flight. Perhaps they had a dynasty of about 10-15 million years before being replaced by other groups.

The Fearbeast is a truly significant find in understanding where these jawed predators come from. Today, arrow worms have menacing bristles on the outside of their heads to capture prey, while the Timorebeast has mandibles on the inside of its head. This is what is seen today in microscopic jawbones: organisms with which arrowheads shared an ancestor more than 500 million years ago. This and other similar fossils provide links between closely related organisms that look very different today. This discovery confirms how arrow worms evolved.

During a series of expeditions to the remote Sirius Passet in the far north of Greenland, more than 82.5˚ north, scientists in this research collected a great diversity of new organisms. Thanks to the remarkable and exceptional conservation offered by the site, they can also reveal interesting anatomical details, including their digestive system, muscular anatomy and nervous system.

* Jakob Vinther is the author of the study and researcher at the Faculties of Earth Sciences and Biological Sciences at the University of Bristo

2024-01-09 04:10:00
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