Despite its large presence in art, though, griffins didn't usually show up in written literature. The griffins most people think of were the ones featured in ancient stories, guarding hoards of gold high in the mountains and defending it against all who desired it. Herodotus mentions this story as being in an epic poem The Arimaspeia by Aristeas of Proconnesus. Pliny and Aelian talk about gold-guarding griffins, too.

In earlier versions of Greek Mythology, Harpies were described as beautiful winged maidens.
Later they became winged monsters with the face of an ugly old woman with crooked, sharp talons.

In early Greek mythology, sirens were actually prophets and described as having bodies of a bird and beautiful human heads.
Some ancient myths say the sirens are the daughters of the river Achelous and the Muse of dancing, Terpsichore the "Whirler."
The numbers and names of the sirens are inconsistant in classical mythology

Large, hairy and by name, abominable. This creature is known across the globe. Canada, America, and The himalayas are just a few examples of the Bigfoots territory.