Tertiary Mammal Evolution in the Context of Changing Climates, Vegetation, and Tectonic Events

Abstract

Evolutiona ry trends among mammals over the past 66 Myr have been profou ndly influenced by changing climat es, in tum the result of tectonic events. The global trop ical forest type of ecosystem of the early Tertiary was disrupted by Late Eocene climatic changes, with the extinction of most archaic mammalian lineages and the appearance of most modem famil ies. Later Tertiary trends reflect increasing aridity, with the appearance of open-habitat mammals such as grazing ungulate s, although true grasslands probably did not appear until the Late Miocene in the New World and the Pliocene in the Old World. Patterns of mammalian diversity track paleote mperature curves for the northern latitudes, with maxima in the early Mid dle Eocene and early Middle Miocene. Major dispersals occurred at times of sea level lows, resulting in loss of endemism in originally isolated continents such as South America and Afr ica, and changes in faunal composition across Holarctica. Dispersal in con junction with climatic changes accounted for maj or extinction events in the Late Eocene to Early Oligoce ne, at the end of the Miocene , and in the mid Pliocene. Outstanding problems include the origin and dispersal routes of many extant orders that appeared at the start of the Eocene and the