Extinct walrus-like mammal discovered in Atlantic provides new insight into marine evolution

Scientists have discovered a previously unknown species of marine mammal, Ontocetus posti, that lived 2.2 million years ago. The discovery, led by Dr Mathieu Boisville from the University of Tsukuba, provides new insights into the evolutionary history of walruses and the impact of environmental change on marine life. The fossilised remains, found in Norwich, UK and Antwerp, Belgium, were initially misidentified but later revealed unique features that set Ontocetus posti apart from its relatives.

A New Look at Evolution

The newly identified Ontocetus posti exhibits several notable features, including four post-canine teeth, a larger lower canine tooth, and a short, fused mandibular symphysis. These features suggest it was a sucking feeder, like modern walruses. Dr. Boisville said the discovery highlights convergent evolution, where different species develop similar features due to similar environmental pressures.

Migration and adaptation

The presence of Ontocetus posti in the North Atlantic illustrates a fascinating migration story. Ontocetus is thought to have originated in the North Pacific Ocean and migrated to the Atlantic via the Central American Seaway, a now-closed oceanic route. As the climate cooled and the seaway closed in the Late Pliocene, the environment changed significantly, likely contributing to the extinction of Ontocetus posti in the Early Pleistocene. This extinction paved the way for the modern walrus, Odobenus rosmarus, which now inhabits the Arctic.

The significance of the discovery

The discovery of Ontocetus posti is crucial to understanding walrus evolution and the impact of past environmental changes on marine mammals. It highlights how species adapt to changing climates and may provide insight into how current and future climate change may affect marine life. Studying such extinct species helps refine our understanding of marine mammal evolution and guides conservation efforts for existing species.

Future Research Directions

This discovery opens up new avenues for research on pinnipeds, including seals, sea lions, and walruses. Future studies could explore other Pleistocene deposits to discover more about the diversity of marine mammals. Each discovery adds to our knowledge of the history of life in our oceans, offering clues about past and present marine ecosystems.