The Matamata turtle, Chelusfimbriatus, may reach a carapace length of 18 inches, and is bizarre in appearance. The shell is exceedingly rough and knobby, each lamina (horny plate) being cone shaped and bearing very well-marked growth rings. The head and neck are large and flat and are covered with numerous protuberances, warts, and ridges.
- Adults are uniformly dark brown or black. The throat area is red, pink, or dull buff. The young have brown carapaces and plastrons.
- The mouth is extremely wide, and the snout is very long, enabling the creature to breathe while almost completely submerged.