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After the fourth extinction, the largest ever, life blossomed as before with all the spare resources and unoccupied niches left around. Cynodonts, the ancestor to mammals, developed differentiated teeth and moved their brains to the back of the skull (0.251 bya) just as mammals have today. Modern ray-finned fish evolved by 0.225 bya in the oceans , and archosuars diverged in to crocodiles, dinosaurs and pterosaurs (0.220 bya)

At the same time as reptiles were evolving much larger forms, Therapsids, also descended from reptiles, were developing things like warm bloodedness, and milk glands, 0.22 bya. This was in the time of the Gymnosperms, who had taken over from the club moss, horsetail, and fern forests that had ruled for over a hundred million years, since 0.38 bya.


The dog-sized amphibian, Euyrops, Texas, 0.295 bya.

After the fourth major extinction event (0.251 bya), reptiles got more specialized in form, and cynodonts, proto-mammals (0.251 bya, got even smarter, with more of their brains devoted to the ability to smell. This helped scavenging for crumbs between the toes of evolving thunder-lizards. By 0.195 bya, the modern mammalian jaw and inner ear had formed in a subsequent proto-mammal, Hadrocodium, allowing better hearing and eating. Proto-birds (0.23 bya diverged from Dinosaurs at just about the same time they diverged from crocodiles and pterosaurs.Dinosaurs kept developing in size, diversity, and specialization for the over 160 million years.

By the way, all this had been occurring on one land mass, Pangea, that had been in place since 0.36 bya, allowing and forcing these species to develop on and with nearly continuous access to each other. By 0.21 bya, Pangaea broke up, into two land masses, Laurentia and Gondwana, beginning the formation of the continents that hosted the entirety of human history. Breaking up the continents accelerated the rates of divergence and specialization in the species, as different forms were freed from competition with each other.

While birds developed feathers (0.19 bya), from their reptilian scales, Hadrocodium developed hair (0.164 bya) from its scales to aid in the warm bloodedness it had for the last 56 million years. These first mammals resembled the platypus, with reptilian and mammalian features, particularly egg-laying. It was not until 44 million years later that marsupials and placentals diverged (0.120 bya).

By 0.15 bya, Laurasia and Gondwana break up and begin to form the continents we recognize today, in the same era as the first angiosperms. Angiosperms, like mammals, were small and opportunistic species with more investment in their youth. In the case of mammals, they were able to offer their children milk (a href=”http://paleontology.wikia.com/wiki/Timeline_of_evolution”>0.22 bya). In the case of angiosperms, they offered erred their sends fruit.   This allowed them to propagate quickly to new sites, an important asset in a time when the antics of dinosaurs could devastate a place in shirt order. By 0.13 bya, Angiosperms had developed flowers elaborate enough to attract insects to carry pollen for them to suitable mates, the beginning of a famous and important relationship in nature. By 0.1 bya, the first bees evolved in this very role.

Now a little over 31/32 the way though the history of life.

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