Entelodont skull (archaeotherium mortoni), USA, South Dakota, Oligocene (30 million years old), length 47 cm, with base

Note: The archaeotherium, also known as "hell's pig" is a family of omnivorous mammals that was extinct about 15 million years ago. Remains of these animals have been found in Europe, America and Asia. 

This is an old specimen that has just been prepared with modern techniques. Few fossiliferous rocks contain fossils of such a beautiful colour. This chocolate coloration is very popular with collectors.