Fossil Fred Hotchkiss is still making discoveries.

This Vineyard Haven octogenarian and marine paleontologist has spent a lifetime studying and sharing science and nature. Last week, Fred showed up in my office with a strange and beautiful shell, and together we identified this uncommon specimen as a spiny oyster.

Spiny oysters are confused and confusing.

Well, actually, it is us who are confused and, perhaps, poor at naming. I suspect spiny oysters know exactly who they are. While this bivalve has some serious spines, it is not an oyster. And these mollusks are more closely related to scallops, though some of their habits do resemble those of oysters. 

Like true oysters, spiny oysters stick to things with a cement-like material that they produce and use to attach themselves to a hard substrate. They can also produce pearls.  Like scallops, spiny oysters have auricles, which are the triangular-like ears at the top or hinge area of their shells.  Unique to their genus is their hinge mechanism, which has a ball-and-socket formation, rather than the toothed hinge of other bivalves.

Confusing is the fact that one of this animal’s shells was found by Fred and his daughter Grace Hotchkiss Scarano, PhD on Mink Meadows beach, since there are no spiny oysters known to live this far north. Spiny oysters, also called thorny oysters, are members of the Spondylus genus, which has more than 70 known species in the world’s tropical and subtropical waters. I could find no records to show that even one was found in local waters before last week. The Atlantic spiny oyster thrives on this coast, but not usually north of the Carolinas.

The shell itself was highly weathered, with holes that are evidence of boring sponge drilling damage. It had a beautiful red edge and mark of an adductor muscle on the interior surface. The tell-tale feature, however, was the ball-and-socket arrangement at its hinge. It wasn’t clear which Spondylus species it was, since the spines had long been gone and the shell was so worn.

Spiny oysters are well known for their shells, history, and uses. Revered in ancient civilizations and present ones, the spiny oyster provides for all. 

Neolithic Europe, Pre-Columbian, Andean, and Mesoamerican civilizations valued this bivalve for its beauty, symbolism, and worth. It was used in ceremony and rituals, buried with the dead, and offered to the gods. The shells and spines were carved into figurines, beads for commerce and jewelry, and held for providence. Spiny oysters symbolized fertility and rain, and were thought to bring agricultural abundance and protection from natural disasters.

Some species are edible, with the adductor muscle providing a food analogous to the part of the scallop we prefer to consume. Other species bioaccumulate a toxin that make them unpalatable and even dangerous to eat.

Today, spiny oysters continue to be valued in the shell, jewelry, and aquarium trades. Fred’s find is especially magical since its story of provenance is so mysterious. It could be a spine-tingling tale of travel and adventure, or perhaps a simple story of a shell collector’s stash being tossed back into the sea. No matter; in my mind the oyster and the man that found them are both Island treasures.

Suzan Bellincampi is director of the Felix Neck Wildlife Sanctuary in Edgartown, and author of Martha’s Vineyard: A Field Guide to Island Nature and The Nature of Martha’s Vineyard.