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A Trellan crocodile is a large, destructive reptile.

After viewing the disarray of Odo's quarters, during one of his frequent trips there to complain about the noise that was otherwise keeping him awake, Quark observed that he knew that if Odo continued to take the form of an animal, he would end up behaving like one. He then accused Odo of being either a Klingon targ, or a Trellan crocodile. (DS9: "Crossfire")