Environment & Science

Meet the hippo-like creature that roamed ancient California

An artists rendering of a desmostylus adult and juvenile. Image by Justin Santos.
An artists rendering of a desmostylus adult and juvenile. Image by Justin Santos.
Artist: Justin Santos

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New research is shedding light on a long extinct California species known as desmostylian. It looked like a hippo and lived along the coast between 8 and 12 million years ago.

Little is known about these lumbering mammals that once romped through local waters, but scientists have pieced together some key details.

For instance, analysis of fossilized teeth show they were plant eaters. A recent study from paleontologists at Cal State Fullerton suggests they also may have lost their teeth as they aged.

"Kind of like how some humans loose all their teeth as they get older," remarked study author and CSUF graduate student Gabriel-Philip Santos.

This finding is based on a unique desmostylian jawbone discovered in 1996, near the 241-toll road in Mission Viejo.

Santos says the alveoli, or teeth sockets of the specimen, were closed. This suggests the animal lost its chompers earlier in life but continued eating without them into old age.

A diagram showing the teeth of desmostylians at various ages.
A diagram showing the teeth of desmostylians at various ages.
Cal State Fullerton

This fossil was found a good 14 miles from today's shore line, but Santos says 10 million years ago much of California was covered in shallow ocean waters.

In fact, there were tons of fascinating marine animals living here back then, like ancient varieties of whales, walruses and large sharks.

"It was a really different time to see the types of animals we had back then," Santos explained.

Scientists don’t know exactly what killed off desmostylian and why they have no direct living relatives today, but research like this helps piece together California's past and give clues about how mammals here evolved over time.

CSUF graduate student Gabriel-Philip Santos and the desmostylian fossil.
CSUF graduate student Gabriel-Philip Santos and the desmostylian fossil.
Eric Scott

Santos says it's also just fun to imagine these almost-elephant sized creatures playing in the waves of Southern California.

"I picture herds of these... walking down the coastline on beaches... that is so weird but cool."