Species of clam thought to exist only as a fossil found alive


A species of clam thought to exist only as a fossil has been found off the coast of California.

It was first described in 1937 by a scientist who collected over a million fossils around Los Angeles.

But an identical living clam was found by Dr. Jeff Goddard while scouring the rocks in search of a species of sea slug called a nudibranch.

Dr Goddard, of the University of California, Santa Barbara, said: ‘It’s not all that common to find a species alive for the first time known from the fossil record, especially in a well-studied region like Southern California.

“Ours goes nowhere near the famed Coelacanth or the deep-sea mollusk Neopilina galatheae – which represents a whole class of animals thought to have disappeared 400 million years ago – but it goes back to the time of all those wonderful animals captured from the of La Brea tar.

Dr Goddard recounted how one afternoon in November 2018, while trawling Naples Point beach, he saw a pair of small translucent bivalves, molluscs that live inside closed shells.

He said: “Their shells were only 10 millimeters long, 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.”

Surprised and believing it to be rare, he left the clam undisturbed but took close-up photos of the animals which he then sent to Paul Valentich-Scott, curator emeritus of malacology at the Santa Barbara Museum of Natural History.

He said: “I was surprised and intrigued. I am very familiar with this family of bivalves along the coast of the Americas. This was something I’ve never seen before.

The curator said he would have to see the animal in person to properly evaluate it, so Dr. Goddard returned to the Naples point but could not find the clam after two hours of searching.

It took him nine more trips to make his rediscovery, in March 2019.

Mr. Valentich-Scott said he was even more surprised once he got his hands on the shell.

He knew it belonged to a genus with one member in the Santa Barbara region, but this shell matched none of them, suggesting the possibility of a new species.

She said: “This really started the hunt for me. When I suspect something is a new species, I have to go back through all the scientific literature from 1758 to the present. It can be a tall order, but with experience it can go quite quickly.

It was then that the two researchers came across George Willett’s 1937 description, which he had named Bornia cooki after Edna Cook, a fellow collector from the region who had found the only two specimens known to exist.

Mr. Valentich-Scott requested the original specimen, now called Cymatioa cooki, from the Los Angeles County Museum of Natural History, which used it as the type specimen, the specimen that defines the species.

Meanwhile, Dr. Goddard had found another live specimen at Naples Point, a single empty shell in the sand under a boulder.

Through careful comparison of the living specimens and the fossil, Valentich-Scott concluded that they were the same species, describing the find as “quite remarkable”.

Wondering how the clam has evaded detection for so long, Dr. also found the shells of our little treasure.

He believes it may have arrived on currents as planktonic larvae, carried in from the south during marine heatwaves from 2014 to 2016.

These have allowed many marine species to extend northward, including several documented specifically at Naples Point.

Depending on the growth rate and longevity of the animal, this could explain why no one had noticed Cymatioa cooki before 2018, including Dr Goddard, who has been working on nudibranchs at Naples Point since 2002.

He said, “The Pacific coast of Baja California has large intertidal boulder fields that stretch for literally miles, and I suspect Cymatioa cooki down there is probably living in close association with animals that burrow under those boulders.”

The results were published in Zookeys journal.

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