Scientists have discovered the fossil remains of a 16 million-year-old fur seal that provides a missing link in the evolutionary chain.

The discovery shed light on a more than five million-year gap in the known evolutionary history of fur seals and sea lions. The researchers named the new species "Eotaria crypta", which means "dawn of the sea lion."

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"Its fossilized partial jaw, with several well-preserved teeth, was recovered from a 15-17 million-year-old rock formation in Southern California in the early 1980s, but until now had been misidentified as belonging to a walrus species," explained Robert Boessenecker from the University of Otago, lead author of the study.

The fossil was deposited in what is now the John D. Cooper Archaeological and Paleontological Center, where Boessenecker discovered it ,as well. He immediately that it was not the small walrus Neotherium but a tiny, early fur seal.

This type of evolutionary gap is known of as a "ghost lineage," and the new research has now eliminated it in terms of history of the fur seal.

Previously, Japanese palaeontologist Naoki Kohno proposed the earliest fur seals most likely lived in the open ocean and were rarely seen around continental shelf areas, where fossils would be visible to scientists. This theory could help explain why fossils of the ancient animal have remained so elusive.

"This was very exciting as fur seals and sea lions have a limited fossil record that, up until now, extended back to about 10-12 million years ago. Yet we know that their fossil record must go back to around 16-17 million years ago or so, because walruses have a record reaching back that far," said Kohno.

Boessenecker said the fossil supported the hypothesis because it collected rocks formed by sediments deposit.

Details of the study were published in the journal Biology Letters.

Tagsfur seal, SEAL, walrus, marine mammals, marine animals, fossil remains, Fossil, seal fossil, walrus fossil, oldest fur seal, evolutionary gap