‘Unicorn of mollusks’: scientists discover mysterious clam, edible and as big as a baseball bat, in Philippines lagoon

For hundreds of years, biologists knew of the giant shipworm - an enormous species of clam more than a metre long - only from shell fragments and a handful of dead specimens.

Those specimens, despite being preserved in museum jars, had gone to mush. Still, the shipworm’s scattered remains made an outsized impression on biologists. Its huge tubular shells were so striking that Swedish taxonomist Carl Linnaeus included the animal in his book that introduced the scientific naming system “Systema Naturae.”

And yet no one could get their hands on a living example of the giant shipworm, or Kuphus polythalamia. Unlike with other shipworms, named because they ate their way into the sides of wooden boats, no one knew where the giant shipworm lived.

“It’s sort of the unicorn of mollusks,” said Margo Haygood, a marine microbiologist at the University of Utah.

The habitat of the world’s longest clam is a mystery no longer. As Haygood and her colleagues reported Monday in the Proceedings of the National Academy of Sciences, the search for the giant shipworm has come to an end.

Television news in the Philippines ended the shipworm’s near-mythical status. A TV station aired a short documentary segment in 2010 about strange shellfish living in a lagoon. The show filmed the mollusks growing in the muck, as though someone had planted rows of elephant tusks.