The Mongolian death worm
The Mongolian death worm, or olgoi-khorkhoi, is a deadly worm described to the zoologist Roy Chapman Andrews on his Mongolian expedition, in an account first printed in English in 1922. Expeditions to the Gobi have looked for it and found nothing.
Roy Chapman Andrews wrote in On the Trail of Ancient Man (1926) that the people he spoke with described the creature in detail although none of them had seen it. They said it was sausage-shaped, about two feet long, with no head or legs, and so poisonous that touching it killed at once. It lived in the emptiest parts of the Gobi. Andrews compared its place for the Mongols to the dragon's for the Chinese. The Premier told him that he had never seen one himself, but that someone he knew had seen one and survived.
Brian Dunning of Skeptoid says the first English account appeared in 1922, when Asia Magazine printed extracts from Andrews's book about his expedition, which the American Museum of Natural History sponsored.
Benjamin Radford, writing for Live Science in 2014, says explorers and television crews have searched the Gobi for the worm many times, interviewing witnesses and setting traps, and every search came back with nothing. Wikipedia reports that in 1983 locals who said they had seen the olgoi-khorkhoi were shown a Tartar sand boa and said it was the same animal.
"None of those present ever had seen the creature, but they all firmly believed in its existence and described it minutely. It is shaped like a sausage about two feet long, has no head nor legs and is so poisonous that merely to touch it means instant death. It lives in the most desolate parts of the Gobi Desert, whither we were going. To the Mongols it seems to be what the dragon is to the Chinese. The Premier said that, although he had never seen it himself, he knew a man who had and had lived to tell the tale."
- Mongolian Death Worm: Elusive Legend of the Gobi Desert, Live Science, Benjamin Radford (2014)
- Olgoi-Khorkhoi: The Mongolian Death Worm (Skeptoid Podcast #344), Skeptoid, Brian Dunning (2013)
- Mongolian death worm, Wikipedia