Museum, University of Nebraska State


Date of this Version



Bulletin of the American Museum of Natural History (285) 139-285.


Copyright 2004 American Museum of Natural History.


Taxon ranges of larger mammalian carnivores can be grouped into seven temporal intervals during the later Cenozoic. These intervals are of varied duration and seem to correspond to periodic faunal reorganizations that accompanied the progressive climatic deterioration occurring from the late Eocene to the Pleistocene. Recent oxygen isotope records from deep-sea cores serve as proxy for the pattern of global climate during the Cenozoic and compare reasonably well with the large carnivore intervals. Intervals A, B, and the early part of C characterize a time of cooler global climate (δ18O: +1.3 to +3.0‰) following the early Eocene climatic optimum. The later part of Interval C, following the mid-Miocene climatic optimum, and Intervals D through F record a gradual climatic deterioration (δ18O: +2.0 to +3.8‰) from the mid-Miocene to early Pliocene. Interval G (δ18O: +3.8 to +5.0‰) corresponds to the extreme global cooling of the later Pliocene and Pleistocene. Glacioeustatic decline in sea level during these intervals probably made possible the entrance of migrant Eurasian carnivores and other mammals into the New World via the Bering route. The periodic emergence of this land bridge and the effect of the climatic oscillations of the later Cenozoic on the mammalian fauna appear responsible for the faunal shifts.