Pachyrhachis is an extinct genus of snake with well developed hind legs known from fossils discovered Ein Yabrud, near Ramallah, in the central West Bank. It is a relatively small snake, about 1 m (3–4 ft) long. Pachyrhachis appears to have been an ancient marine snake; the fossils occur in a marine limestone deposit, and the thickened bone of the ribs and vertebrae would have functioned as ballast to decrease the buoyancy of the animal, allowing it to dive beneath the ancient Cretaceous seas that it once inhabited.