The many species of spiny or thorny oysters vary considerably in appearance and are actually related to scallops, rather than oysters. Similar to oysters however, they live cemented to rocks, corals or other hard surfaces and are capable of producing pearls, depending on their environment.
This family has a very well developed middle mantle and nervous system, with sensory tentacles and multiple eyes around the shell edges. Spiny oysters have a ball and socket type connection between the two shell parts, rather than the more common toothed hinge of other bivalves.
Spiny oysters are filter feeders and can suck water into its gills to remove oxygen and food.