2. Mammalia Though mammals predate the dinosaurs, it was only once the dinosaurs were mostly gone that the mammal adaptive radiation began in earnest The defining features of extant mammals are their hair, mammary glands, larger brains, differentiated teeth, modified jaws, etc. The mammal lineage predates the mammals with the synapsids: the mammal-like reptiles
Etchings come from Vertebrate Peleontology by Alfred Sherwood Romer, The University of Chicago Press, Chicago, 1966. Fig. 155 comes from p. 108 and Fig. 259 comes from p. 174.