the concept that major evolutionary changes tend to take place in stages, not all at once.
Source: Relethford, J.H. (1997). The human species: An introduction to biological anthropology. Mayfield Publishing Company: Mountain View, CA.
the retention of ancestral characteristics in combination with new ones.
Source: Cummings, M.R. (1996). Biology: Science and life. West Publishing Company: St. Paul, MN
Archeopteryx- an early bird-like fossil with characteristics of dinosaurs like teeth, tail, hind legs, and brain, and bird like features like feathers and a wishbone.
Primatelike mammals have shown primate features like the teeth (molar teeth), base of the skull, structure of the ankle, and climbing ability.