Researchers Find Living Clam Thought to Have Gone Extinct Thousands of Years Ago

While looking for sea slugs in California, a marine ecologist came across the tiny, ten-millimeter mollusks

A clam
Scientists have discovered the first living C. cooki specimen. Jeff Goddard

Marine ecologist Jeff Goddard was searching for sea slugs in the tide pools of a California beach near Santa Barbara when something strange caught his eye: two tiny translucent white clams. Goddard was surprised—he had studied California’s intertidal habitats for decades, but had never seen anything like these delicate little mollusks, per a statement.

At the time, in November 2018, he didn’t realize he was looking at a species that scientists believed had gone extinct thousands of years ago.

“Their shells were only ten millimeters long,” Goddard, a researcher at the University of California, Santa Barbara, says in the statement. “But when they extended and started waving about a bright white-striped foot longer than their shell, I realized I had never seen this species before.”

Not wanting to disrupt a possible breeding pair, he did not collect the animals. Rather, he snapped some pictures and sent them off to his colleague, Paul Valentich-Scott, curator of malacology at the Santa Barbara Museum of Natural History. 

Valentich-Scott wasn’t exactly sure what they were either. To be certain, he’d need a specimen to examine in person. But the clams were evasive—Goddard returned to the spot nine times before he was able to find a clam to bring back to Valentich-Scott, per KCLU’s Lance Orozco.

Originally, they thought the clam was likely to be a new species, per the statement. The pair began searching the fossil record to prove it. But then, in a paper from 1937, they tracked down illustrations for a species called Bornia cooki (now reclassified as Cymatioa cooki). The clam had been discovered by amateur shell collector Edna Cook, who found the only two known specimens after recognizing their uniqueness in a collection of 30,000 fossils from a deposit in the Baldwin Hills, Los Angeles. 

Clam next to a chiton
The minuscule C. cooki, marked with an arrow, sits next to a chiton in the tidepools of Naples Point, California. Jeff Goddard

Paleontologist George Willett described the species and named it after Cook. Later research determined that marine deposits in the Baldwin Hills dated to between 28,000 and 36,000 years ago. Scientists have presumed C. cooki has been extinct for tens of thousands of years, writes Allison Gasparini for Science News

But Goddard and Valentich-Scott thought the clam resembled the species they’d found, so they requested Willett’s specimen from the Natural History Museum of Los Angeles County to compare. 

“Once I physically saw that original specimen that Willett had used for his description, I knew right away” that it was the same, Valentich-Scott tells Science News. The pair published the first report of a living C. cooki specimen last week in ZooKeys.

“It’s rare to find something first as a fossil and then living,” David Jablonski, a paleontologist at the University of Chicago who was not involved in the research, tells Science News

Scientists aren’t sure how the species stayed hidden for so long, but it’s possible the clams live in a remote area farther south. Marine heatwaves between 2014 and 2016 may have washed clam larvae north, per the paper. 

“It’s super exciting,” Goddard tells KCLU. “It’s always exciting to find something new. Doubly exciting to find something new literally in our backyard.” 

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