In North Greenland, in the Early Cambrian Sirius Passet fossil location,
fossils of a novel class of animal predators have been found. These massive
worms might represent some of the first carnivorous creatures to have
entered the water column over 518 million years ago, exposing an unknown
predatory lineage from the past.
The Latin term for the new fossil creatures is Timorebestia, which
translates to "terror beasts." Some of the biggest aquatic animals of the
Early Cambrian era had features such as gigantic jaw structures within their
mouths, a distinct head with long antennae, fins along the sides of their
bodies, and a length of more than 30 cm.
"Prehistoric arthropods, like the weird-looking anomalocaridids, were the
dominant predators during the Cambrian," said Dr. Jakob Vinther, a senior
author of the study and member of the University of Bristol's Schools of
Earth Sciences and Biological Sciences. On the other hand, Timorebestia is a
near but distant relative of chaetognaths, or living arrow worms. These
days, these ocean predators are substantially smaller and consume minuscule
zooplankton."
"Our research shows that these ancient ocean ecosystems were fairly
complex, with a food chain that allowed for several tiers of
predators."
"Timorebestia would have been on the top of the food chain and were giants
in their day. That puts its significance on par with that of some of the top
predators found in today's waters, such sharks and seals, which existed
throughout the Cambrian period."
The bones of a common swimming arthropod named Isoxys were discovered by
the researchers inside the fossilized digestive tract of Timorebestia. "We
can see these arthropods were a food source for many other animals," said
Morten Lunde Nielsen, who is involved in the present work and was a former
Bristol Ph.D. student.
The species was widespread at Sirius Passet and has long, forward- and
backward-pointing defensive spines. They obviously weren't able to fully
escape that destiny, though, since Timorebestia gobbled them up in large
amounts."
Among the earliest Cambrian animal fossils are arrow worms. Arrow worms
date back at least 538 million years, whereas arthropods first emerge in the
fossil record between 521 and 529 million years ago.
"Arrow worms and the more primitive Timorebestia were both swimming
predators," Dr. Vinther clarified. Therefore, we might assume that, before
arthropods became popular, they were most likely the predators that ruled
the waters. It is possible that their monarchy lasted for around 10–15
million years before they were surpassed by more prosperous
populations."
Participating in the research, Luke Parry from Oxford University said,
"Timorebestia is a really important discovery for understanding the origins
of these jawed predators." Timorebestia possesses jaws within its head, but
modern arrow worms have frightening bristles on the exterior of their heads
for snaring prey."
"Microscopic jaw worms today exhibit characteristics similar to those of
their ancestors over half a billion years ago—organisms that arrow worms
shared." Timorebestia and similar fossils provide connections between
closely related species that have extremely diverse appearances
today."
The second senior author and head of the field mission, Tae Yoon Park of
the Korean Polar Research Institute, continued, "Our discovery firms up how
arrow worms evolved." A unique nerve area on the abdomen of living arrow
worms is known as a ventral ganglion. It is exclusive to these
creatures."
"We have discovered this preserved in Amiskwia, another fossil, and
Timorebestia. Whether Amiskwia was closely linked to arrow worms as part of
its evolutionary stem lineage has been a topic of contention. This theory
has a lot more support now that these distinct ventral ganglia have been
preserved."
"The discovery of such unusual predators in Sirius Passet excites us much.
Through many journeys to the extremely isolated Sirius Passet, located at
82,5˚ north in North Greenland, we have gathered an impressive array of
novel and fascinating species. We are also able to show fascinating
anatomical characteristics, like as their nervous system, muscles, and
digestive system, because to Sirius Passet's extraordinary
preservation."
"We have many more exciting findings to share in the coming years that will
help show how the earliest animal ecosystems looked like and evolved," Dr.
Park said.
