Teeth found in Norwich (UK) and Antwerp (Belgium) have been identified as belonging to a newly described species of extinct marine carnivore, much like a modern-day walrus.
The animal, named Ontocetus posti, may have shared the walrus’ unique method of suction feeding, according to a new paper published today in PeerJ Life & Environment.
The walrus (Odobenus rosmarus) is one of the most well-known animals of the Arctic, thanks to its sheer size – and the heart-breaking sequence in an episode of Netflix’s Our Planet, where David Attenborough narrates the tragic fall of several walruses from a cliff in an attempt to return to the sea. The species is unique in its suction feeding ability for extracting the flesh of molluscs.
Although the walrus is the only surviving member of the Obodenidae family, the fossil record is relatively diverse with species spread over a wider distribution than the extant walrus.
The taxonomy of the extinct Ontocetus genus has been under debate for decades, and will likely continue to change as known fossils are re-examined and new fossils are discovered. The fossil specimens had been described as different species, then later grouped under Ontocetus emmonsi.
This particular study focused on mandibles (lower jaws) found in the North Sea – a pair near Norwich in England from the Pleistocene (the ‘Ice Age’), and a third from Belgium from the previous epoch, the Pliocene. The work has resulted in the description of a new species.
What’s particularly intriguing about the newly described Ontocetus posti is its similarity to the modern-day walrus. The unique combination of features on its mandibles is enough for the scientists to both describe it as a new species, and to suggest that it was able to suction-feed, like a walrus.
“When I was a master student, I studied a fossil walrus mandible [from Belgium], and I noticed that this mandible was different from all the fossil walrus mandibles,” says Mathieu Boisville, lead author and a doctor in palaeontology at the University of Tsukuba in Japan.
“We conclude that the mandible had dental and mandibular characteristic of both Ontocetus emmonsi, but also the extant walrus Odobenus rosmarus.”
It's thought that Ontocetus posti became extinct during the Early Pleistocene as a result of global cooling, and the walrus – which is better adapted for cooler waters – was later able to fill the same ecological niche.
Find out more about the study: Boisville M, Chatar N, Kohno N. 2024. New species of Ontocetus (Pinnipedia: Odobenidae) from the Lower Pleistocene of the North Atlantic shows similar feeding adaptation independent to the extant walrus (Odobenus rosmarus)
Main image: Artist's impression of Ontocetus posti. Credit Jaime Bran
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