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Long before the first sharks appeared, large predatory worms were the “terror monsters” of the seas 500 million years ago, according to new research.
Scientists have discovered fossils of previously unknown worm species during expeditions in northern Greenland, revealing what they believe are some of the earliest carnivores.
The worms reached lengths of about 30 centimeters and were some of the largest swimming animals during that period, known as the early Cambrian Period.
The researchers named the worms Timorebestia, which means “terror monsters” in Latin. Fins ran down the sides of their bodies, and their distinctive heads had long antennae and massive jaws.
It was previously believed that primitive arthropods, including strange-looking distant relatives of crabs and lobsters called Anomalocaris, were at the top of the marine food chain during the Cambrian Period, which lasted from 485 million to 541 million years ago.
But predatory worms were an important part of the ecosystem 518 million years ago and scientists didn’t even know they existed until they found fossils. A study describing the findings was published Wednesday in the journal Science Advances.
Senior study author Dr. “Timorebestia were giants of their time and were near the top of the food chain,” Jakob Vinther said in a statement. .
“This makes it equivalent to some of the top carnivores in modern oceans, such as sharks and seals from the Cambrian period,” Vinther said. “Our research shows that these ancient ocean ecosystems were highly complex, with a food chain that allowed for several layers of predators.”
Vinther said that “animals evolved explosively for the first time” during the Cambrian Period, when carnivorous predators emerged. “It had a tremendous impact on carbon and nutrient cycles, as well as the pace of evolution.”
Following an evolutionary path
These predatory worms are distant relatives of much smaller modern arrow worms, or chaetognaths, that feed on zooplankton, Vinther said.
Dartwolves are considered to be among the oldest animals to appear during the Cambrian period. Arthropods first appeared between 521 and 529 million years ago; Evidence for arrow worms shows that they existed as early as 538 million years ago.
“Both arrowworms and the more primitive Timorebestia were swimming predators,” Vinther said. “So we can guess that these were probably predators that dominated the oceans before arthropods appeared. Perhaps they had a dynasty of about 10-15 million years before they were replaced by other, more successful groups.”
Preserved within the fossilized digestive system of Timorebestia was Isoxys, a swimming arthropod with long, protective spines pointing forward and backward.
“However, they did not entirely manage to avoid this fate because Timorebestia trampled them in large quantities,” study co-author Morten Lunde Nielsen, a former PhD student at the University of Bristol, said in a statement.
Revealing details about Timorebestia opens a window into the worms’ evolutionary timeline from half a billion years ago to the present, researchers said.
Oxford University paleobiology professor Luke Parry, one of the authors of the study, said in a statement: “While arrowworms today have menacing hairs on the outside of their heads to catch their prey, Timorebestia has jaws on the inside of its head.”
“This is what we see today in microscopic jaw worms, organisms with which dart worms shared an ancestor half a billion years ago. Timorebestia and other fossils like it provide connections between closely related organisms that look very different today.”
senior study author Dr. D., principal research scientist at the Korea Polar Research Institute. Tae-Yoon Park said that modern arrow worms have a different nervous system in their abdomen, called the ventral ganglion, and this was also found preserved in Timorbestia. The detection of a nervous system in another fossil called Amiskwia suggests that the soft-bodied animal is also evolutionarily related to arrow wolves.
A remote but rich fossil bed
Park led a team of researchers on expeditions to the Sirius Passet, a well-preserved fossil site in the farthest reaches of northern Greenland. The sun shines all day at the remote location, 600 miles (966 kilometers) from the North Pole, Vinther said. There’s a small window of time each year, about six weeks, when the site is accessible, but it’s worth the journey, researchers said.
“Fossils are so dense here compared to other areas that every time you break up the rock you uncover dozens, hundreds of soft-bodied fossil organisms,” Vinther said.
Members of the research team are eager to return to Sirius Passet, where they discovered fossilized remains of other relatives of Timorebestia, to better understand the ocean’s early food chain.
“Thanks to the remarkable, extraordinary preservation of the Sirius Passet, we can also reveal exciting anatomical details, including the digestive system, muscular anatomy, and nervous systems,” said Park. “We have many more exciting findings in the coming years that will help show how the earliest animal ecosystems looked and evolved.”
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