Not any specific animal, but any animal (or person) that had gross deformities or severe birth defects might have been called a "monster" before about the middle of the twentieth century.

We still use a few words with the Greek stem teras. For example, teratology is the study of monstrosities (i.e. birth defects).

In Classical Arabic, the word that today means "monster" was used to refer to animals, or perhaps more specifically, wild (undomesticated) animals.