GEOL 107 Lecture Notes - Lecture 25: Flowering Plant, Biogeography, Feathered Dinosaur
6 Nov 2017
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We have seen that the permian tetrapod assemblages were dominated by synapsids (pelycosaurs. Cowen, 2013, chapter 15 in the early permian, therapsids in the late permian) with fewer diapsids (lecture 18) Diapsids evolved into dinosaurs, birds, lizards and snakes (lectures 19 and 23) Only living group of the synapsids are the mammals. The most advanced therapsids were the cynodonts (permian-triassic) These are directly traceable into the earliest mammals with innumerable intermediate forms. The problem is not in finding missing links , it is in having so many intermediate forms that it becomes difficult to define exactly when a near-mammal became a mammal . Evolving mammalian characters in the skeleton included: increasingly complex teeth and tooth replacement reduction in the number of bones in the lower jaw simultaneous increase in the number of bones in the inner ear fully upright stance. These were accompanied by non-skeletal features including: full thermoregulation live birth milk production.
