A team of paleontologists has made a remarkable discovery—a new species of extinct walrus-like mammal named Ontocetus posti.
This species, which lived approximately 5.3 million years ago during the Pliocene epoch, was identified from fossilized remains found in Norwich, England, and Antwerp, Belgium.
The discovery, published today in the journal PeerJ, highlights the fascinating case of convergent evolution, where Ontocetus posti developed feeding adaptations remarkably similar to those of the modern walrus, despite the significant time gap and different environmental conditions.
The Discovery and Its Significance
The fossils of Ontocetus posti were initially thought to belong to another species, Ontocetus emmonsi, but a detailed analysis of the mandibles revealed unique features that distinguish it as a new species. These features include the presence of four post-canine teeth, a larger lower canine, and a fused and short mandibular symphysis, which suggests that Ontocetus posti was well adapted to suction-feeding—a feeding technique similar to that used by modern walruses.
According to the study’s lead researcher, Dr. Mathieu Boisville from the University of Tsukuba in Japan, "This discovery provides new insights into the evolutionary history of walruses, showing how different species adapted to similar environmental challenges over millions of years."
The research emphasizes how environmental changes, such as global cooling during the Late Pliocene, influenced the extinction of Ontocetus posti and the emergence of cold-adapted modern walruses (Odobenus rosmarus).
Understanding Marine Mammal Evolution
The discovery of Ontocetus posti offers valuable insights into the evolutionary history of marine mammals, particularly walruses. The migration of the Ontocetus genus from the North Pacific to the Atlantic Ocean during the Mio-Pliocene transition highlights the impact of significant geological events, such as the closure of the Central American Seaway, on the distribution and evolution of marine species. As global cooling set in during the Late Pliocene, species like Ontocetus posti were unable to adapt to the changing conditions, leading to their extinction and the rise of species better suited to cold environments.
This discovery also sheds light on the broader patterns of marine mammal evolution, particularly the role of convergent evolution in shaping similar adaptations among different species. The fact that Ontocetus posti developed feeding adaptations akin to those of modern walruses suggests that similar ecological pressures can lead to the evolution of comparable traits, even in species separated by millions of years.
The Future of Paleontological Research on Walruses
The team behind this discovery hopes to uncover more fossils related to Ontocetus posti to further understand the species' adaptations and the environmental changes that influenced its evolution. The researchers also aim to explore the broader implications of these findings for the study of marine mammal evolution, particularly in understanding how past climate changes shaped the development of current species.
Dr. Boisville and his colleagues believe that this discovery highlights the importance of conservation efforts for modern walruses, which are currently facing significant challenges due to human activity and global warming. "The modern walrus is strongly impacted by human activity, whether it be hunting or global warming, affecting its habitat and thus its prey," Boisville noted. "We hope that this discovery can reinforce the idea behind conservation of these beautiful but vulnerable animals."