Amphisbaena by parkerart

The amphisbaena is a two-headed lizard or serpent. It has one head in the normal position, and another at the end of its tail. It can therefore run in either direction. Its eyes shine like lamps, and has no fear of cold.The name "amphibaena" is now given to a legless lizard that can move either forward or backward, though this is a relatively modern use of the name.

Historical References:

Lucan [1st century CE] (Pharsalia, book 9, verse 843-844):
"Dread Amphisbaena with his double head / Tapering...".

Pliny the Elder [1st century CE] (Natural History, Book 8, 35):
The amphisbaena has a twin head, that is one at the tail-end as well, as though it were not enough for poison to be poured out of one mouth.

Isidore of Seville [7th century CE] (Etymologies, Book 12, 4:20):
The amphisbaena has two heads, one in the proper place and one in its tail. It can move in the direction of eaither head with a circular motion. Its eyes shine like lamps. Alone among snakes, the amphisbaena goes out in the cold.