Diplocaulus
(Varies by Species)

Living during the Permian period, Diplocaulus is one of the most instantly recognizable prehistoric animals — not for its size, but for its extraordinary boomerang-shaped head. This ancient amphibian's skull extended outward into two long, sweeping horns that gave it a shape unlike anything alive today. The leading theory is that this shape acted like a hydrofoil, allowing water flowing over the head to generate lift and help it maneuver in rivers and lakes — a biological rudder built into its skull!