Fabulous animals play a significant role in Myth and Legend, to the extent that many were included in Pliny the Elder's pioneering Natural History and in medieval Bestiaries. Many were incorporated into heraldic devices, which conserved their familiarity and their symbolic authority, and no Travellers' Tale in any era could be deemed truly satisfying unless it included at least one such creature.
The boundary between animals "known to science" and those which are not has never been made entirely clear; a subspecies of fantasy, close to the borderline of Science Fiction, deals with ambiguous cases, as exemplified in Robert W Chambers's In Search of the Unknown (coll 1904). Modern fantasy has been remarkably promiscuous in deploying fabulous animals, for exactly the same purposes as did ancient Myths – mostly for use as "straw monsters" to be slain (or possibly tamed) by ambitious heroes. Genre Fantasy makes particularly abundant use of Dragons and Unicorns, having reformulated their typical roles – and hence their potential symbolism – in the direction of benignity. Other generic types sufficiently important to warrant individual consideration are Sea Monsters and winged horses.
Most fabulous animals are compounded out of ill-matched parts of real animals, thus belonging to the class of chimeras, named after the Chimera, mentioned in Homer's Iliad, which had the foreparts of a lion, the middle of a goat and the hindparts of a snake. The gryphon (griffin) has an eagle's head and wings, the rest of its body being a lion's. The sphinx sets a humanoid head on a lion's body (adding wings in the Greek version); the manticore adds a scorpion's tail and exotic teeth to a similar assembly. A modified griffin, called a hippogriff or "griffin horse", was invented by Ariosto for Orlando Furioso (1516). The other common strategy employed in the making of Monsters is, of course, giantism, but it is doubtful whether the results really qualify as "unknown to science" except in cases where obvious extremism is combined with an element of exotic symbolism, as in Jeremias Gotthelf's The Black Spider (1842) and the movie King Kong (1933).
Jorge Luis Borges's useful guide to fantastic Biology, The Book of Imaginary Beings (1967), includes descriptions of all the above-mentioned species plus the Amphisbaena (a snake with a head at each end), the Basilisk or Cockatrice (a snake or lizard whose gaze is credited with the power to kill), Harpies (vultures with human heads), the Hydra (a multi-headed creature which grows two new heads whenever one is cut off), the Salamander (a lizard-like creature able to live in fire) and many others of more idiosyncratic provenance and more limited use. A useful bibliography of references to traditional fantastic creatures is Margaret W Robinson's Fictitious Beasts (1961 chap).
Modern fantasy writers have found difficulty making significant additions to the range of fabulous creatures (> Imaginary Animals for discussion), occasionally retreating into unrepentant vagueness after the fashion of Lewis Carroll, who never specified what snarks and jabberwocks looked like. The It of Theodore Sturgeon's "It" (1940) and Angela Carter's Odd in Miss Z, The Dark Young Lady (1970) are modern examples. Nasty creatures are usually ugly in name as well as manner, as per H P Lovecraft's shoggoths, J R R Tolkien's orcs (a frequently borrowed term which, confusingly, was originally used to describe a kind of sea monster) and Stephen R Donaldson's ur-viles. [BS]
see also: Mythical Creatures.