This chapter looks into early avemetatarsalians and the origin of Dinosauria. From the period of late Triassic and Mesozoic, Avemetatarsalia is a large and diverse clade including many familiar extinct vertebrates, such as pterosaurs and non-avian dinosaurs like birds. Moreover, Avemetatarsalians decoupled the functions of the fore and hindlimbs, which then allowed the subsequent evolution of bipedalism and flight. The chapter also looks into the biology, characteristics, and evolution of pterosaurs, ornithischians, and sauropodomorphs. It mentions how the origin and diversification of birds coincided with an increase in the body size of pterosaurs, which suggested that birds may have outcompeted pterosaurs at small body sizes.
Chapter
Avemetatarsalia and the Origin of Dinosauria
Chapter
Geography and Ecology of the Cenozoic
This chapter explores the geography and ecology of the Cenozoic era. It cites how changes in continental positions have affected Earth's climates and the ability of vertebrates to disperse between its regions. By the late Mesozoic era, continental separation and epicontinental seas had isolated populations of terrestrial tetrapods and freshwater vertebrates, which limited possibilities for their migration between continents. While the best-known Cenozoic extinction took place at the end of the Pleistocene era, and this mainly affected only larger land animals. The chapter also considers debates on whether Pleistocene extinctions were mainly caused by climate changes or the spread of humans across the globe.
