A Trellan crocodile is a creature.
Trellan crocodiles originate from the salt flats of Trellus V. Trellan crocodiles are dangerous as they release sulphuric acid from sacs in their mouths when they bite. (ST module: Creatures)
In 2372, Quark wondered if Odo had destroyed his quarters on Deep Space 9 by taking the form of a Trellan crocodile. (DS9 episode: "Crossfire")