Five million years ago, before the Ice Ages, strange mammals resided along the Pacific coast near modern San Francisco, Calif.

Walruses with short, twin tusks lounged on the beaches. Dwarf baleen whales, relatives of blue whales, filtered tiny creatures from the sea water. A dentally-deranged porpoise with a “chin” longer than its upper jaw shared the sea with the dwarf whales.

Primitive forms of porpoise and a dolphin related to the extinct Chinese river dolphin also lived in the region.

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Along with the strange extinct beasts, modern-type species also dwelt in the region, including northern fur seals and right whales, during the late Miocene and Pliocene Epochs, which ended approximately 2.5 million years ago.

Robert Boessenecker, geology doctoral student at the university of Otago, recently published a description of the fossilized remains of the ancient northern Pacific marine animals in the journal Geodiversitas.

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“The mix of marine mammals I ended up uncovering was almost completely different to that found in the North Pacific today, and to anywhere else at that time,” Boessenecker said in a press release. “At the same time as this eclectic mix of ancient and modern-type marine mammals was living together, the marine mammal fauna in the North Atlantic and Southern Ocean were already in the forms we find today.”

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Geography isolates the distinct community of the pre-Ice Age northern Pacific. The Bering Strait in the north was still closed, allowing terrestrial movement between Asia and North America, but keeping the animals from the Arctic and Atlantic Oceans at bay.

In the south, Central America and South America had collided, creating the Isthmus of Panama and blocking movement from the Caribbean to the Pacific. Warm tropical waters also blocked movement of northern species.

Image: A speculative life rendering of the fossil whale Balaenoptera bertae unearthed in the San Francisco Bay Area. Credit: Robert Boessenecker.