SPECIES LONGEVITY IN NORTH AMERICAN FOSSIL MAMMALS

Species longevity in the fossil record is related to many paleoecological variables and important to macroevolutionary studies, yet there are very few reliable data on average species durations in Cenozoic fossil mammals. Many of the online databases (such as MIOMAP, NEOMAP, and the Paleobiology Database) use only genera in North American Cenozoic mammals, and there are severe problems because many key groups (e.g., camels, oreodonts, peccaries, pronghorns, proboscideans) have no reliable updated taxonomy, with many invalid genera and species and/or many undescribed genera and species. Most of the estimates of species longevity have been mere guesses without sufficient data to back them up. The few published data sets yield species duration estimates of about 2.3-4.3 m.y. for larger mammals, with small mammals tending to have shorter species durations. My own compilation of all the valid species durations in families with updated taxonomy (39 families, containing 431 genera and 998 species, averaging 2.3 species per genus) yields a mean duration of 3.21 m.y. for larger mammals. This breaks down to 4.10-4.39 m.y. for artiodactyls, 3.14-3.31 m.y. for perissodactyls, and 2.63-2.95 m.y. for carnivorous mammals (carnivorans plus creodonts). These averages are based on a much larger, more robust data set than most previous estimates, so they should be more reliable for any studies that need species longevity to be accurately estimated.