Fossils of a new group of animal predators have been discovered in the Early Cambrian Sirius Passet fossil locality in North Greenland. These large worms might have been among the earliest carnivorous animals to have colonised the water column over 518 million years ago, revealing a past dynasty of predators previously unknown to scientists.
The newly found fossil animals were named Timorebestia, meaning ‘terror beasts’ in Latin. Adorned with fins down the sides of their body, a distinct head with long antennae, massive jaw structures inside their mouth, and growing to more than 30cm in length, these were some of the largest swimming animals in the Early Cambrian times.
Dr Jakob Vinther from the University of Bristol’s Schools of Earth Sciences and Biological Sciences, a senior author on the study, mentioned that primitive arthropods were recognized as dominant predators during the Cambrian, such as the anomalocaridids. However, he stated that Timorebestia is a distant, but close, relative of living arrow worms, or chaetognaths, which are much smaller ocean predators today that feed on tiny zooplankton.
He further explained that the research suggested ancient ocean ecosystems were fairly complex, with a food chain supporting several tiers of predators. Timorebestia would have been close to the top of the food chain, similar in importance to some of the top carnivores in modern oceans, such as sharks and seals back in the Cambrian period.
The researchers found remains of a common, swimming arthropod called Isoxys inside the fossilised digestive system of Timorebestia. Morten Lunde Nielsen, a former PhD student at Bristol and part of the study, mentioned that the arthropods were common at Sirius Passet and had long protective spines, yet they were preyed on by Timorebestia in significant quantities.
The study also highlighted that both arrow worms and the more primitive Timorebestia were swimming predators, possibly dominating the oceans before arthropods took over, lasting around 10-15 million years before other groups superseded them.
Luke Parry from Oxford University, who was part of the study, emphasized Timorebestia’s significance in understanding the origins of jawed predators. He pointed out the similarities and differences between present-day arrow worms and Timorebestia, highlighting that these fossils provide links between seemingly disparate modern organisms.
Senior author Tae Yoon Park from the Korean Polar Research Institute expressed enthusiasm about the discoveries made at Sirius Passet. He highlighted that the exceptional preservation allowed revealing anatomical details, providing insights into the earliest animal ecosystems and their evolution.
Source: ‘A giant stem-group chaetognath’ by Tae-Yoon Park, Jakob Vinther et al in Science Advances.