Robert Boessenecker, a PhD student with the University of Otago, has discovered an extinct species of whale that lived during Pliocene, 3.35 – 2.5 million years ago.

The newly discovered whale has been named Balaenoptera bertae in honor of Prof Annalisa Berta from San Diego State University.

It belongs to the same genus as minke and fin whales, indicating that the Balaenoptera lineage has lasted for about 3 million years.

Mr Boessenecker unearthed the Balaenoptera bertae’s incomplete skull at the Purisima Formation in the San Francisco Bay Area in 2005. It was encased in a hard concretion that took five years to remove.

“Balaenoptera bertae would have been approximately 5-6 meters in length, slightly smaller than modern minke whales,” said Mr Boessenecker, who is the author of a paper published in the journal Geodiversitas.

Mr Boessenecker in his study has also put together a record of 21 extinct species of marine mammals that inhabited the North Pacific in the Pliocene.

“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.”

“Primitive porpoises and baleen whales were living side-by-side with comparatively modern marine mammals such as the Northern fur seal and right whales.”

“And species far geographically and climatically removed from their modern relatives also featured, such as beluga-like whales and tusked walruses, which today live in the Arctic.”

Mr Boessenecker added: “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.”

“This strange fauna existed up until as recently as one or two million years ago. Its weirdness was likely maintained by warm equatorial waters and barriers to migration by other marine mammals posed by the newly formed Isthmus of Panama, and the still-closed Bering Strait.”

“Once the Bering Strait opened and the equatorial Pacific cooled during the Ice Age, modernized marine mammals were able to migrate from other ocean basins into the North Pacific, leading to the mix we see today,” Mr Boessenecker concluded.

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Robert W. Boessenecker. 2013. A new marine vertebrate assemblage from the Late Neogene Purisima Formation in Central California, part II: Pinnipeds and Cetaceans. Geodiversitas 35 (4): 815-940; doi: 10.5252/g2013n4a5