When it swam the seas that covered California some 10 million years ago, it might have looked something like a slender hippo — but with longer legs, broad webbed feet, and rows of teeth jutting from its mouth like the notches on a backhoe’s bucket.

The world today knows none of its direct descendants, but its closest living relatives can be found among both elephants and manatees.

Excavators first unearthed the fossil of this 2.5-meter long mammal in 1998, while trenching a golf course in suburban Orange County, California.

Now, 15 years later — including 3 years on display in a Los Angeles museum — a paleontologist has determined that the animal is a genus and species that’s entirely new to science. [Read about another aquatic giant recently discovered in a museum: “Giant-Headed Sea Monster Found in Kansas Museum“]

The specimen, a juvenile, is the most complete skeleton of its kind ever found — a member of an extinct family of ocean-going mammals whose lifestyle was unlikely enough that, when first discovered in the 1930s, they were thought to have been enormous amphibians.

They were later given the name Paleoparadoxiids: “ancient paradoxes.”

Now Dr. Lawrence Barnes, curator emeritus of vertebrate paleontology at the Natural History Museum of Los Angeles County, where the specimen has been on view since 2010, has published new research identifying the unique characteristics of that qualify the creature as its own phylogenetic enigma.

Writing in the journal Contributions in Science, Barnes calls the new genus Neoparadoxia, or “new paradox.”

Like other Paleoparadoxiids, Neoparadoxia likely spent most of its life in the ocean near shore, where it browsed on sea grasses, surfaced long enough to gulp in air through its nose, and came on land perhaps only long enough to take drinks of fresh water.

Unlike other members of its family, however, Barnes estimates that adults of the new species were as long as 2.7 meters, making them the largest known Paleoparadoxiids.

And at about 10.5 million years old, the Orange County juvenile is also the most historically recent example of the family.

This, Barnes suggests, may explain some of its more developed, derived traits, like broader feet, a more streamlined cranium, and extra molars that came in later in life.

With only five other known species of this unusual family, the nearly complete skeleton of Neoparadoxia may yield important new data about this and other “ancient paradoxes.”



Lawrence G. Barnes (2013). A New Genus and Speices of Late Miocene Paleoparadoxiid (Mammalia, Desmostylia) From California Contributions in Science (521), 51-114 ISSN 2165-1868.