Fig. 1.

A) Mesozoic creatures and landscape. Life reconstruction of the late Jurassic. Note the diverse integuments and appendages present in the dinosaurs, Mesozoic birds and early mammals.

Reptiles: Caudipteryx (1), Sinosauropteryx (2), Psittacosaurus (3, a beaked dinosaurs); Sinornithosaurus (4), Pterosaurs (5, dinosaurs glide with skin flaps). Birds: Confuciusornis (6), Changchengornis (7), Liaxiornis (8, a small toothed bird). Mammals: Zhangheotherium (9, an early mammal). For 1 - 5, see table 2 and section 3. From Hou et al., 2003. P. 38. Painted by Anderson Yang.

B) Different developmental stages of skin appendage morphogenesis. The principles of skin formation are the same in reptile, birds, and mammals. From dermatomyotomes and other sources, dermal cell precursors migrate in and build presumptive skin and appendages with regional specificities. They share similar hierarchical morphogenesis but acquire variations that lead to different skin appendage phenotypes. Modified from Chuong and Homberger, 2003.