by Ben S. Roesch
All sharks (and "bony" fish) have "tongues", though they aren't much like ours, or any other tetrapod (the "four-limbed" non-fish vertebrates) for that matter. Therefore, shark and fish "tongues" aren't called tongues at all--they are called basihyals. The basihyal is found on the floor of the mouth of sharks and fishes, just as our tongue is placed on the floor of our mouths. But that's about where the similarity ends! Whereas tongues in tetrapods are generally large (or long), flexible and extremely useful, the basihyal is basically just a small, stout, and only vaguely tongue-like piece of cartilage. It is the forward-most part of the basibranchial, a cartilaginous bar-like structure running down the midline of the shark or fish's chest that supports the lower gill-related bones.
In most sharks, the basihyal is small, relatively immovable, and generally useless. In some sharks, however, such as the orectoloboids (carpet sharks) and heterodontoids (bullhead sharks), the basihyal is larger, more flattened and movable, and is used to suck up prey in conjunction with powerful pharyngeal muscles.
And of course we cannot forget Isistius spp. (the cookiecutter sharks), which employ their large basihyal (powered with strong rectus cervicis throat muscles) to suck "flesh-cookies" out of cetaceans, pelagic fishes, other sharks, pinnipeds, and squids that have been bitten by the shark (Shirai and Nakaya 1992). The strong "oral vacuum" involved in this feeding strategy is also aided by extremely large and sharp teeth, thick lips, and, possibly, rotationary movement of the body.
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