Ancient Seas Ruled by Newly Unearthed Giant Carnivorous Worms
Fossils of colossal predator worms, Earth's ancient carnivores, have been unearthed by researchers These gigantic creatures dominated the seas 518 million years ago, marking a significant milestone in tracing the evolutionary journey of early predators
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During expeditions in North Greenland, scientists uncovered fossils of a previously unknown worm species, revealing what they believe to be among the earliest carnivorous animals. These worms, which reached almost 1 foot (30 centimeters) in length, were some of the largest swimming animals of the early Cambrian Period.
The worms were given the name Timorebestia, which is Latin for "terror beasts," due to their appearance. They had fins along their bodies and unique heads with long antennae and large jaws.
Prior to this discovery, it was thought that primitive arthropods, such as the peculiar distant relatives of crabs and lobsters known as Anomalocaris, were the dominant predators in the marine food chain during the Cambrian Period, spanning from 485 million to 541 million years ago.
The predator worms played a crucial role in the ecosystem 518 million years ago, a surprising discovery that scientists only made after uncovering the fossils. The findings of the study were published on Wednesday in the journal Science Advances.
"Timorebestia were formidable creatures in their time and likely held a prominent position in the food chain," remarked Dr. Jakob Vinther, senior study author and associate professor in macroevolution at the University of Bristols Schools of Earth Sciences and Biological Sciences, in a statement.
Vinther stated that this places it on par with some of the most significant carnivores in today's oceans, like sharks and seals during the Cambrian period. "Our study indicates that the ancient ocean ecosystems were quite intricate, with a food chain that supported multiple levels of predators."
Vinther also mentioned that during the Cambrian Period, with the emergence of carnivorous predators, "animals experienced an explosive evolution for the first time." He added, "This had a significant impact on the carbon and nutrient cycles, as well as the speed of evolution."
Tracing an evolutionary path
These predator worms are distant relatives of the much smaller modern arrow worms, or chaetognaths, that feed on zooplankton, Vinther said.
Arrow worms, believed to be one of the oldest animals that emerged in the Cambrian Period, predate arthropods which first appeared between 521 and 529 million years ago. Evidence indicates that arrow worms existed as early as 538 million years ago.
Using an electron microprobe technique, scientists were able to map the carbon in a Timorebestia fossil and uncover detailed anatomical features such as fin rays and muscle systems, as depicted in the diagram on the right. Dr. Jakob Vinther led the research.
"According to Vinther, both arrow worms and the more primitive Timorebestia were predatory swimmers. It is likely that they dominated the oceans before arthropods became dominant, possibly for a period of 10-15 million years before being replaced by other, more successful groups. The fossilized digestive system of Timorebestia contained Isoxys, a swimming arthropod with long protective spines pointing in both directions."
"Despite their efforts to avoid that fate, Timorebestia still managed to consume them in large numbers," explained Morten Lunde Nielsen, a coauthor of the study and former doctoral student at the University of Bristol.
The researchers stated that gaining insights into Timorebestia's characteristics offers valuable information about the evolutionary history of worms from half a billion years ago to the present day.
In 2023, numerous new species were identified, such as the Hyperolius ukaguruensis, a spiny-throated reed frog. This particular species was found in the Ukaguru Mountains of Tanzania and is known for its lack of vocalization.
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"Today, arrow worms have developed menacing bristles on the exterior of their heads to capture prey, while Timorebestia possesses internal jaws," stated Luke Parry, coauthor of the study and associate professor of paleobiology at the University of Oxford.
"Microscopic jaw worms, which share a common ancestor with arrow worms over 500 million years ago, exhibit similar traits. Fossils like Timorebestia bridge the gap between organisms that are closely related but appear vastly different today."
Modern arrow worms have a ventral ganglion nervous system, which was found preserved in Timorebestia, according to senior study author Dr. Tae-Yoon Park of the Korea Polar Research Institute. The same nervous system was also observed in another fossil, Amiskwia, indicating an evolutionary relationship between the two soft-bodied animals.
Park headed a research team that embarked on expeditions to Sirius Passet, a remarkably well-preserved fossil site in the most remote parts of North Greenland. The sun shines continuously in this isolated location, situated 600 miles (966 kilometers) from the North Pole, Vinther stated. Researchers have only a brief six-week window each year when the site is accessible, but the journey is well worth it, according to Vinther.
"The concentration of fossils here is so much higher than in any other location, that every time you split the rock, you uncover dozens to hundreds of soft-bodied fossil organisms," Vinther explained.
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The researchers are excited to revisit Sirius Passet, where they found fossilized remains of other species related to Timorebestia, in order to further explore the ancient ocean's initial food chain.
"Thanks to the incredible level of preservation in Sirius Passet, we are able to uncover fascinating anatomical details, such as their digestive system, muscle anatomy, and nervous systems," stated Park. "We anticipate sharing even more groundbreaking discoveries in the future, which will provide insight into the appearance and development of the earliest animal ecosystems."
