The British paleontologist Derek W. Ager describes how the fossil record poses a major difficulty for the theory of evolution: The point emerges that if we examine the fossil record in detail, whether at the level of orders or of species, we find—over and over again—not gradual evolution, but the sudden explosion of one group at the expense of another. (Derek A. Ager, “The Nature of the Fossil Record”, Proceedings of the British Geological Association, Vol. 87, 1976, p. 133.) One fossil that proves that its species never passed through any intermediate stages is the 32-million-year-old Tasmanian devil skull pictured here.