Giant clam
From Tardis Wiki, the free Doctor Who reference
Giant clams were one of the products of Davros' early experiments. They were kept under the Kaled Dome in a cave leading out to the wastelands. The Fourth Doctor said that its bite had the force to crush bone. A giant clam bit Harry Sullivan's leg as he and the Doctor were exploring the caves. The Doctor subdued it by hitting it with a rock. (TV: Genesis of the Daleks)