Show 4 1 j THE FIRST MAMMALS i I nv nr Percy ICI W Cobb JJ n. S S. S M. M I D. D t Gaft g I y l 1 r t I l c cJ 4 I J a a. DOG DOG- While tho the warm warm birds were developing by slow degrees from rom the first tree Inhabiting reptiles some lomo of or this same some class clan of ot reptiles progressed along an entirely different line These finally branched out to become the most highly developed class of oC animals in existence the existence the mammals Those first mammals of some years ears ago began to develop a more highly specialized 1 and complicated organism Their blood warm warm- warmed warmed ed up They breathing apparatus became separated by a n wall from their digestive o mechanism Their heads hearts and skeletons developed to a higher degree than titan those of ot earlier animals But most significant of ot nil 11 they began to breed their young oung within their own bodies and to feed them after birth by b means of newly newly- developed mammary glands from Crom which their name name mammal Is derived These animals could then live and breed on the dry land and wore were oreno no longer at nt the mercy merc of tho cold as their cold blooded reptilian an an- ancestors ancestors were wee Scientists point to proof of or the mammals mammal's origin from rom tho the reptile In the skull of tho the or dog toothed dog toothed reptile which was dug out of o the racks of or the Triassic ago age and lived about aboul years ago The skull and especially the teeth are similar to those of or the tho modern dog Even today toda there thero aro are mammals that lay eggs just like the reptiles a 8 a link Unk in the evolution of or mammals from rom reptiles I |