Ontocetus is one of the most notable extinct odobenines owing to its global distribution in the Northern Hemisphere.
Reassessment of a pair of mandibles from the Lower Pleistocene of Norwich (United Kingdom) and a mandible from the Upper Pliocene of Antwerp (Belgium) that were referred to as Ontocetus emmonsi reveals existences of features of both Ontocetus and Odobenus.
In the Press
Huge teeth found in Norwich belong to extinct walrus-like animal that vacuumed prey into its mouth, say scientists
I Am the Walrus but This Fossil Was Not
Extinct Walrus-Like Species Discovered: New Insights into Marine Mammal Evolution
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New species of extinct walrus-like mammal discovered in the North Atlantic
New species of extinct walrus-like mammal discovered
Extinct walrus-like mammal that sucked prey in prehistoric times discovered
Dr. Mathieu Boisville
University of Tsukuba
For All Readers - AI Explainer
Q&A: New Species of Ontocetus in the North Atlantic
What is the significance of the new species of Ontocetus described in this research?
The new species, Ontocetus posti, highlights a unique feeding adaptation that is similar to but independent of the modern walrus (Odobenus rosmarus). This discovery provides insights into the evolutionary paths and ecological niches occupied by extinct odobenines in the Northern Hemisphere during the Lower Pleistocene.
Where was the new species of Ontocetus discovered, and what fossils were reassessed?
The new species was identified through the reassessment of a pair of mandibles from the Lower Pleistocene of Norwich, United Kingdom, and a mandible from the Upper Pliocene of Antwerp, Belgium. These fossils showed a mix of features from both Ontocetus and Odobenus.
What are the key anatomical features that identify Ontocetus posti?
Key features of Ontocetus posti include:
- Four post-canine teeth, including the first premolar (p1).
- A lower canine that is larger than the cheek-teeth.
- A lower incisor (i2).
- A fused and short mandibular symphysis.
- A well-curved mandibular arch.
- Thin septa between teeth.
These features suggest an adaptation to suction-feeding.
How does Ontocetus posti’s feeding adaptation compare to the extant walrus?
Ontocetus posti shows anatomical adaptations for suction-feeding similar to those found in the modern walrus (Odobenus rosmarus). However, these adaptations evolved independently, indicating a similar ecological niche despite not coexisting.
What does the research suggest about the geographic distribution and migration of Ontocetus?
Ontocetus originated in the Late Miocene in the western North Pacific and quickly spread to the Atlantic Ocean during the Pliocene. Its fossils have been found in regions including England, Belgium, the Netherlands, Morocco, and the eastern United States. The species likely migrated via the Central American Seaway and colonized the western North Atlantic during the Early Pliocene, later spreading to the North Sea during warmer periods of the Late Pliocene.
Why did Ontocetus posti become extinct, and how did climate changes affect its survival?
Ontocetus posti likely went extinct around 1.7 million years ago due to global climate cooling during the Early Pleistocene. The cooling isolated the North Sea from the North Atlantic and impacted mollusk faunas, which were crucial to the diet of suction-feeders like Ontocetus posti. The species was unable to adapt to these abrupt climate changes, contributing to its extinction.
Did Ontocetus and Odobenus coexist in the North Atlantic, and how did Odobenus rosmarus eventually dominate?
Ontocetus and Odobenus did not coexist in the North Atlantic. Odobenus appeared nearly a million years after the extinction of Ontocetus. Odobenus rosmarus is more cold-tolerant and adapted to cooler climates, allowing it to survive and eventually dominate as the sole surviving walrus species.
What future research directions does the study suggest?
Future research aims to explore the past diversity of Ontocetus and Odobenus on a global scale. This could shed light on the evolutionary history and adaptations that led to the eventual dominance of the cold-tolerant Odobenus rosmarus.
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