Being a rabid fan of Jorge Luis Borges, I ordered a copy of the latest edition of the previously scarce Book of Imaginary Beings, and found that the entry for the Perytion (sic- the original Spanish name for the beast was peritio reveals some...uh... problems:
The Sibyl of Erythraea, it is said, foretold that the city of Rome would finally be destroyed by the Perytons. In the year A.D. 642 the record of the Sibyl's prophecies was consumed in the great conflagration of Alexandria; the grammarians who undertook the task of restoring certain charred fragments of the nine volumes apparently never came upon the special prophecy concerning the fate of Rome. In time it was deemed necessary to find a source that would throw greater light upon this dimly remembered tradition. After many vicissitudes it was learned that in the sixteenth century a rabbi from Fez (in all likelihood Jakob Ben Chaim) had left behind a historical treatise in which he quoted the now lost work of a Greek scholiast, which included certain historical facts about the Perytons obviously taken from the oracles before the Library of Alexandria was burned by Omar. The name of the learned Greek has not come down to us, but his fragments run:
"The Perytons had their original dwelling in Atlantis and are half deer, half bird. They have the deer's head and legs. As for its body, it is perfectly avian, with corresponding wings and plumage. . . . Its strangest trait is that, when the sun strikes it, instead of casting a shadow of its own body, it casts the shadow of a man. From this, some conclude that the Perytons are the spirits of wayfarers who have died far from their homes and from the care of their gods. . . . . and have been surprised eating dry earth . . . flying in flocks and have been seen at a dizzying height above the Columns of Hercules. . . . they [PerytonsJ are mortal foes of the human race; when they succeed in killing a man, their shadow is that of their own body and they win back the favor of their gods. . . . and those who crossed the seas with Scipio to conquer Carthage came close to failure, for during the passage a formation of Perytons swooped down on the ships, killing and mangling many. . . . Although our weapons have no effect against it, the animal-if such it be-can kill no more than a single man. . . . wallowing in the gore of its victims and then fleeing upward on its powerful wings. . . . in Ravenna, where they were last seen, telling of their plumage which they described as light blue in color, which greatly suprised me for all that is known of their dark green feathers. Though these excerpts are sufficiently explicit, it is to be lamented that down to our own time no further intelligence about the Perytons has reached us. The rabbi's treatise, which preserved this description for us, had been on deposit until before the last World War in the library of the University of Dresden. It is painful to say that this document has also disappeared, and whether as a consequence of bombardment or of the earlier book burning of the Nazis, it is not known. Let us hope that one day another copy of the work may be discovered and again come to adorn the shelves of some library."
So, the only sources which mention the peritio have been destroyed, and the first mention of it in an extant document is in a work by a known trickster. Yeah, we've been played by a master- the guy who would have us believe that Don Quixote was written by a Frenchman named Pierre Menard.
The Wikipedia entry for the peryton has been corrected to reflect the peryton put-on but other wikis haven't been updated to reflect the circumstantial evidence that Borges punked us. This particular juxtaposition from Monstropedia is unintentionally hilarious:
The Peryton (or winged dear) is a legendary creature combining physical features of a stag and a bird.
The earliest verifiable account of the peryton occurs in Jorge Luis Borges' Book of Imaginary Beings, in which he refers to a now-lost medieval manuscript as a source. The word is completely unknown in sources from Classical antiquity and from morphological and thematic characteristics one could conclude that if is not a completely modern invention, neither could it be of any origin earlier than the medieval period. The concept of the peryton seems to have become widely known due to its inclusion in the first edition Monster Manual from the popular role-playing game Dungeons and Dragons.
Borges dedicated the story There Are More Things to H.P. Lovecraft- it's tempting to picture the perytion as a fictional relative of the Shantak, or perhaps a winged horror, the multi-branching tentacles of which (used for sanguivorous purposes no doubt) were mistaken for antlers.