Morphometrical analyses of Mammuthus columbi from the Dent Site, Weld County, Colorado

Excavations at the Dent site, northeastern Colorado (USA), in 1932 and 1933 recovered well-preserved partial remains of 14 individual mammoths (Mammuthus columbi) and projectile points in fine colluvial sand on a terrace of the South Platte River. This paper presents morphometrical analyses of the Dent mammoth sample based on dentitions and postcranial elements stored in the Denver Museum of Natural History, Denver, Colorado. Although individual ages vary (2-43 African Elephant-Equivalent Years) and the majority of individuals in the sample (n = 8) are reproductively immature, the latest Pleistocene Dent mammoths (14C age = 10,800 yBP) were relatively small individuals, congruent with the sizes of penecontemporary M. columbi from the Lehner site, Arizona. Morphometrical comparisons of Dent with an earlier, interstadial sample from Hot Springs, South Dakota (14C age = c. 26,000 yBP), is constrained, however, by the special taphonomic pathways at Hot Springs that accumulated almost exclusively the remains of male mammoths. In addition, Hot Springs includes the remains of two different mammoth species, M. columbi and M. pri - migenius. Thus differences between Hot Springs and other localities including Dent and Lehner (Arizona) are explained primarily by considerations of taphonomy, taxonomy, age, and sex, and only in part by evolutionary processes on the North American Plains. Comparisons of samples such as Dent with Hot Springs nevertheless support the hypothesis that late Pleistocene populations of mammoths were organized - like those of modern elephantids - into matriarchal family units (as at Dent) representing a kin group of sexually immature males and females of all ages, as well as into units composed exclusively of reproductively mature males (as at Hot Springs).