Adaptive Radiation of Mammalian Orders

At the end of the Cretaceous period 65 MYBP [Million Years Before Present], only two lineages of eutherian mammals were present: Protoeutheria [an insectivore-like group] and Condylarthra [a hoofed group] [noneutherian Marsupialia, Monotremata, and multituberculates, an extinct group resembling rodents, are also present]. Following the disappearance of dinosaurs at the K/T [Cretaceous / Tertiary], there is a rapid evolution of new mammalian types. By the middle of the Eocene epoch (45 MYBP), most of the twenty or so present-day mammalian orders are identifiable, including forms as diverse as Chiroptera [bats] descended from Protoeutheria and Cetacea [whales] descended from Condylarthra. This rapid evolution of morphological and taxonomic diversity is an example of an adaptive radiation.

Text material © 2005 by Steven M. Carr