Winged and whirring, those forms grew larger each moment, and the traveller knew his stumbling was at an end. They were not any birds or bats known elsewhere on earth or in dreamland, for they were larger than elephants and had heads like a horse's. Carter knew that they must be the Shantak-birds of ill rumour, and wondered no more what evil guardians and nameless sentinels made men avoid the boreal rock desert.
"It was hard work ascending, for the Shantak-bird has scales instead of feathers, and those scales are very slippery."
~ -H.P. Lovecraft, Dream-Quest Of Unknown Kadath

Shantaks are a species of flying bird-like creatures. They are larger than elephants in size, and are said to have heads resembling those of horses. Very few humans are known to have seen them in person.