A 13-year-old found a 5-million-year-old fossil, and now there's a new species of walrus named in his honor

• A 13-year-old fossil enthusiast found a walrus skull in a boulder in northern California in 2011.
• Eleven years later, a paleontologist has named the formerly unknown extinct species after him.

In 2011, a 13-year-old fossil hunter on a beach near bluffs in Santa Cruz, California, happened across the find of a lifetime: the complete skull of an unknown 5-million-year-old walrus species encased in a giant boulder.

His discovery has now led to the identification of that ancient species of walrus, which scientists named after the 13-year-old in his honor in a recent paper published in the peer-reviewed Journal of Vertebrate Paleontology.

Finding fossils

An enthusiast since the age of 9, Forrest Sheperd would go hunting two to three times a week, finding shells, shark teeth, and whale bones.

"I was just absolutely on fire and ecstatic about finding fossils," he told Business Insider.

"I had been fossil hunting enough to know what fossilized bone looks like," he said.

So when he came across the boulder, he recognized from the shape that it was probably encasing a skull, and he, with the help of a friend, hauled the 70-pound rock back to his parents' car.

Sheperd, who's in medical school now, credits the paleontologist at the Santa Cruz Museum of Natural History with identifying many of his fossil finds and connecting him with Robert Boessenecker, an expert in marine mammal fossils.

Eleven years after Sheperd found it, Boessenecker named the newly identified walrus species Valenictus sheperdi after Sheperd's last name.

"This fossil was found by a 13-year-old kid," Boessenecker told BI. "I think that's really remarkable."

Ironically, Boessenecker used to comb the same beach looking for fossils. "I've been going there since I was 15, so Forrest got luckier than I did," he said.

Toothless not tuskless

Between graduate school and earning his doctorate, Boessenecker took more than a decade to free the skull, but as he finally started to remove the hard sandstone surrounding it, he realized there were no sockets in its jaw for teeth, just a place for its upper tusks.

The lack of teeth was a clear sign the skull didn't belong to modern walruses since modern species have teeth, which they use to communicate by clacking together but not to eat with.

Boessenecker determined the skull belonged to the genus Valenictus — the closest extinct relative to living walruses.

But because the new skull was older and larger than other Valenictus species and had some physiological differences, Boessenecker suspected it was an unknown species.

He promised to name it after Sheperd.

"That's obviously such a huge accomplishment for any fossil collector to be able to not just find a cool fossil, but to be able to find a fossil that really contributes to our understanding in a big new way," Sheperd said.

The walruses of California

Millions of years ago, more than a dozen walrus species roamed the planet. Today, only two subspecies are left, "which tells us something weird has happened with walruses in the past couple million years," Boessenecker said.

Ancient walruses used to live in California, which probably had a similar climate 5 million years ago to what it has now, Boessenecker said. That's wildly different from the frigid Arctic temperatures today's walruses prefer.

Between 2 million and 7 million years ago, something happened to the west coast that caused a lot of species to disappear.

"There's all sorts of weirdos that you find in rocks" in California from that time, Boessenecker said. In addition to walruses, there were odd-looking marine mammals, unusual extinct birds, and strange fish.

"We had giant bony-toothed birds flying around up until about 2 million years ago or so," he said. A lot of Valenictus' bizarre companions started disappearing around the same time.

"So what happened on the west coast?" Boessenecker posed. "Why did we have this incredible species or faunal turnover?"

He said scientists thought it had to do with a dramatic change in the geography of the California coastline that occurred about 3 or 4 million years ago.

Before the change, the Los Angeles Basin and southern San Joaquin Valley were shallow marine bays that made perfect foraging grounds for walruses and other marine mammals.

But changes in climate and the emergence of the Sierra Mountains both contributed to the loss of those marine bays and the walruses' food supply, Boessenecker said.

"I like to focus on these sorts of young fossils because it gives us a little bit of perspective on what we still have on the California coastline," Boessenecker said. "It's an incredible ecosystem, and it's changed quite a bit in the past few million years."