Bored holes are quite common, particularly in shells, both modern and fossil. Some are the work of predatory snails that rasp a tapering hole through the shell to get at the delicate meal inside. Borings are made in
These California snails show neat holes bored by a cannibalistic cousin to reach the meal inside. Pleistocene.
The clam that bored into this ancient Florida coral became a fossil while resting in its burrow. Miocene; Tampa, Florida.
living and dead shells (also corals and even solid rock) by barnacles, which leave behind a characteristic sac-shaped hole, often very small. Modern shells worked over by barnacles are common on Florida beaches. Worms leave tiny, narrow tubular borings that may be curved or branch-
ing. Small sponges have left similar borings, often radiating from some central point. Bryozoans and boring corals leave tiny tubelike holes, again most commonly in shells.
Everyone is familiar with teredo wood, which has become the official state rock of North Dakota. The teredo (or shipworm) is just as active today as it has been ever since it first made its appearance in the fossil record in the Jurassic period. The teredo is not a worm but a clam turned lumberjack. It is a member of the pelecypod (clam) suborder Adesmacea, comprising clams that bore. The teredo drills into wood, quickly riddling unprotected wooden piling, docks, and ship hulls. Teredo-bored logs are not uncommon in petrified wood, and occasionally a piece is found with the teredo still in place, its burrow, like itself, turned to solid agate.
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