Oldest fur seal identified, ending five-million-year 'ghost lineage'

February 11, 2015, University of Otago
The oldest known fur seal has been discovered by a Geology PhD student at New Zealands' University of Otago , providing a missing link that helps to resolve a more than 5-million-year gap in fur seal and sea lion evolutionary history. Credit: Robert Boessenecker

The oldest known fur seal has been discovered by a Geology PhD student at New Zealand's University of Otago, providing a missing link that helps to resolve a more than 5-million-year gap in fur seal and sea lion evolutionary history.

Otago's Robert Boessenecker and colleague Morgan Churchill from the University of Wyoming have named this new genus and species of fur seal Eotaria crypta. The genus name Eotaria means 'dawn sea lion'.

The discovery of the seal is newly published in UK Royal Society journal Biology Letters.

The species was tiny, with adults being only slightly larger than a sea otter and around the size of a juvenile New Zealand fur seal, says Mr Boessenecker.

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.

The fossil was deposited in what is now the John D. Cooper Archaeological and Paleontological Center, where Mr Boessenecker found it while searching through its collections.

He says he instantly realized that it was not the small walrus Neotherium but a tiny, early fur seal.

"This was very exciting as fur seals and sea lions—the family Otariidae—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—the closest modern relative of the otariids—have a record reaching back that far," he says.

In palaeontology, a gap like this is known as a 'ghost lineage', and the new research has now eliminated it. "Until now we had no fossil evidence for the first five million years of fur seal and sea lion evolution. It's extremely satisfying to have remedied that," he says.

Mr Boessenecker says Eotaria crypta's status as a critical transitional fossil is revealed through its teeth which are intermediate between the simplified teeth of modern sea lions and the complex bear-like teeth of the earliest known pinnipeds.

"The mystery remains of why there has only been one of these fur seals ever found given that there have been extensive fossil excavations of similarly aged rocks in California," he says.

A Japanese palaeontologist, Dr Naoki Kohno, has previously proposed that the earliest fur seals lived in the open ocean and only rarely strayed into continental shelf areas where they would be more likely to be preserved as fossils.

"This hypothesis is supported by this fossil having been collected from rock formed by sediments deposited in what was then continental shelf, rather than extensively studied inland sites, such as Sharktooth Hill, that formed in bays.

Explore further: Scientists cast doubt on earlier 'killer walrus' claims

More information: The oldest known fur seal, rsbl.royalsocietypublishing.or … .1098/rsbl.2014.0835

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1 / 5 (4) Feb 11, 2015
Again the dating methods have been found to be flawed and not testable after 50 thousand years.Most sites like these will not go into detail on the dating methods and their inaccurate reading because of the flaws as Stanford, UNC, and Columbia Universities have all proven itto be flawed. .
5 / 5 (6) Feb 11, 2015
icshiloh1980, your comment is, of course,false, as most deniers of evolution are. First, you left out that 50,000 year accuracy of dating only applies to carbon 13 - carbon 14 dating techniques. After that, radiometric dating is used. Radiometric dating is extremely accurate and when dating fossils, more than one method is used. Sometimes three or four methods. This gives the age testing validity. Your comment that these afore mentioned universities have proven dating wrong is an outright lie. You sir are no scientist, you are hereby busted.
5 / 5 (5) Feb 11, 2015
jcshiloh: There are 15 main dating methods including radioactive chronometer elements such as uranium, strontium, rubidium, potassium, argon, iodine, barium and more. Some of these elements have half-lives in excess of a billion years.

The results have clearly been found to be consistent across their various overlapping testing periods.

So get real! Your ideas are idiotic. The Earth is not 6,000 years old.

Steve 200mph Cruiz
5 / 5 (4) Feb 11, 2015
Radioactivity makes sense, I swear it does. If it didn't make sense to you, study it until you know everything about it.

We have a plethora of medical and energy technologies available to us today because of scientists understanding of radioactivity, in fact simply measuring the amount of a radioactive material is about the most simple thing you could possibly do with that knowledge. There is no serious doubt in our ability to date fossils like this, multicellular life isn't that old.

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