Pliny the Elder, a Roman author in the first century AD, listed a number of strange creatures, and the Achlis was one of them.
It is described as an elk with a large upper lip, which made it graze backwards. Its back legs had no joints but was still incredibly fast. The downside of this was that the creature couldn' lay down on the ground to sleep or rest, it had to stand up and were sometimes found leaning against a tree. This made it easy for hunters to catch them.