Molluscivore

From Palaeos.org

A pair of the Late Triassic (Carnian age) placodonts, Henodus chelyops (Sauropsida,Sauropterygia,Placodontia,Henodontidae,) dabbling in the muck of a Tethyan lagoon. These strange animals fed on molluscs, as indicated by their broad crushing teeth, and were the reptilian equivalent of walruses and also, in Henodus' case, turtles. Illustration (c) Stanton F. Fink

A molluscivore is any animal that specializes in feeding on mollusks, primarily snails and or bivalves, and sometimes brachiopods, too. Known molluscivores include numerous predatory (and often cannibalistic) molluscs, including octopi, murexes, decollate snails and oyster drills, arthropods such as crabs and fireflies, and, of course, vertebrates including fish, birds and mammals.

The first, and most obvious line of defense for most mollusks is the shell, and molluscivores have developed various methods of circumventing the shell. One method, popular especially with vertebrate molluscivores, is to simply break the shell, either by exterting force on the shell until it breaks (often by biting), hammering away at the shell (done by oystercatchers and crabs), or by simply dashing the victim upon a rock, the last method being most popular among song thrushes and sea gulls. Most molluscivorous vertebrates, like the prehistoric walrus Gomphotaria pugnax, placodonts and the mosasaur Globidens, have powerful jaws filled with flat, or rounded teeth which smash through the shell with a minimum of chipping.

Another method is to simply remove the shell from the prey, though, this is literally easier said than done. Molluscs are attached to their shell via muscular ligaments, thus making the shell's removal, at the very least, an awkward and messy process. Molluscivorous birds, such as oyster catchers and the Everglades snail kite, insert their elongate rhostrum into the shell in order to sever these attachment ligaments, facilitating greater ease in removing the now-hamstringed prey. The carnivorous terrestrial pulmonate snail known as the "decollate snail," ("decollate" being a synonym for "decapitate") employs a very similar method, in that it reaches into the opening of its prey's shell, and bites through the muscles in its prey's neck, whereupon it immediately begins devouring the fleshy parts of its victim. The larvae of glowworms and fireflies, on the other hand, are simply small enough to enter the shell of their prey and begin eating immediately. The modern walrus uses a "tongue piston" to simply suck its prey out of its shells.

A third method is employed by molluscs themselves. Octopi, nautilii, and most molluscivoruous snails use their radula to drill a hole through the shell, then inject venom and digestive enzymes through the hole, whereupon the digested prey is then sucked out through the hole.

Finally, in some cases, the victim is simply swallowed, shell and all. Only cannibalistic sea slugs, snail-eating cone shells (Conus), and some sea anemones employ this particular method.

Those marine predators that feed primarily on squid and other cephalopods are refered to as being "teuthophagus" ("squid-eating").