The climatic changes of the late Jurassic and Cretaceous provided for further adaptive radiation. The Jurassic was the height of archosaur diversity, and the first birds and eutherian mammals also appeared. Angiosperms radiated sometime in the early Cretaceous, first in the tropics, but the even temperature gradient allowed them to spread toward the poles throughout the period. By the end of the Cretaceous, angiosperms dominated tree floras in many areas, although some evidence suggests that biomass was still dominated by cycad and ferns until after the Cretaceous–Paleogene extinction. COUNT 5
QSN1 What event produced further adaptations during  the Jurassic and Cretaceous periods? ANS1 climatic changes QSN2 When was the top of archosaur diversity? ANS2 Jurassic QSN3 What species spread towards the poles during the Jurassic? ANS3 Angiosperms QSN4 What species dominated many tree floras by the end of the Cretaceous period? ANS4 angiosperms QSN5 What types of species are thought to still have been dominate until after the extinction? ANS5 cycad and ferns