[Animals] They capture a species of living fossil clam in the seas of California for the first time

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The species to which the living fossil clam belongs disappeared 400 million years ago from Earth. Today, copies survive in the US.
It happened in the Santa Barbara sea, southern California. Among the salty waters, a team of scientists identified a small white mollusk. As they approached it, they realized that the animal shared characteristics with an ancient species, which inhabited the Earth at least 400 million years ago. Before their eyes, they had a living fossil clam specimen.

"Discovering a new species is always exciting," the UC Santa Barbara researchers write in a statement, "but so is finding a live one that everyone assumed had been lost to time." They found it just off the coast of Naples Point, which surprised scientists even more: this region had been extensively studied, and they had never found signs of prehistoric life before.

According to UC Santa Barbara records, the living fossil clam specimen belongs to a species of mollusk that was abundant in the Pleistocene. This period was characterized, documents the Geominero Museum of Spain, "by a fauna of marine molluscs with a majority of species identical to the current ones". It seems that these animals are still roaming the Earth.

The research began in 2018, when study lead author Jeff Goddard was looking for sea slugs off the coast of Santa Barbara. While he was flipping rocks, he accidentally came across a pair of translucent bivalves. The molluscs immediately caught his attention, even though they were less than 10 millimeters:

“BUT WHEN THEY SPREAD OUT AND STARTED SHAKING A BRIGHT WHITE-STRIPED FOOT LONGER THAN THEIR SHELL, I REALIZED I HAD NEVER SEEN THIS SPECIES BEFORE,” THE AUTHOR RECALLS ABOUT HIS EXPERIENCE.

After recording his find with photographs, Goddard took the specimens for laboratory study. Comparing it with known prehistoric species, he, along with his research team, concluded that they were Cymatioa cooki, as they explain to the magazine Zookeys. Scientists are amazed that "the clam evaded detection for so long," they write in a statement, since Southern California has a long tradition of collecting shells for scientific purposes.

What is such an ancient clam doing in the waters off Santa Barbara?

Goddard suspects that the living fossil clam specimen, as well as other micro-molluscs, were brought to southern California by marine heat waves. Especially between 2014 and 2016, this phenomenon "allowed many marine species to extend their distribution to the north, including several documented specifically in Naples Point", explains the specialist.

This could explain why no one had recorded it before, even though the area has been extensively studied for decades. It is not yet clear what the growth rate and longevity of these animals are, the researchers explain. However, the fact that the species has persisted for more than 400 million years is in itself remarkable.

Even so, Goddard thinks that these prehistoric molluscs inhabit the wide intertidal rock fields of the Californian Pacific: "I suspect that down there Cymatioa cooki probably lives in close association with animals that dig under those rocks", concludes the specialist.

https://www.ngenespanol.com/animales/encuentran-una-almeja-fosil-viva-en-california/