The salamander in flames, of frequent occurence in heraldry, is of this class. Like the toad, ‘ugly and venemous’, the salamander was regarded by the ancients with the utmost horror and aversion. It was accredited with wondrous qualities, and the very sight of it ‘abominable and fearful to behold.’

From Fictitious and Symbolic Creatures in Art by John Vinycomb, p8

The fictitious beings used as symbols in heraldry may be divided into two classes:

(1) Celestial beings mentioned in Holy Writ, and those creatures of the imagination which, from the earliest ages, have held possession of men’s minds, profound symbols unlike anything in the heavens or in the earth beneath or in the waters under the earth…

(2) Animals purely heraldic, such as the heraldic tiger, panther incensed, heraldic antelope, &c., owe their origin and significance to other ideas, and must be accounted for on other grounds, namely, the mistaken ideas resulting from imperfect knowledge of these objects in natural history…

Fictitious and Symbolic Creatures in Art, by John Vinycomb, p6