New Data on Trunk Morphology in the Woolly Mammoth, Mammuthus primigenius (Blumenbach)

A well-preserved trunk (proboscis) of the woolly mammoth (Mammuthus primigenius) found in 2010 in the area of the Oiyagosskii Yar, about 30 km west of the mouth of the Kondratievo River (Yakutia) is described (mammoth named Yuka). The distal part of trunk has a transverse expansion. In the expanded condition, it changes the trunk cross section from oval to ellipsoidal. The expansion is laterally framed by skin folds with sites of muscles making the trunk cross diameter twice as great. Trunk expansion has been recorded in three mammoths: Yuka, Kolyma mammoth, and Kirgilyakh mammoth calf. Structural details of the trunk expansion of the Kirgilyakh mammoth calf and Yuka are almost completely identical. This morphological feature distinguishes trunk of M. primigenius from Loxodonta africana and Elephas maximus ones, the cross section of which remains oval throughout the trunk extent. The adaptive value of this unique trunk structure of the woolly mammoth in connection with cold climate conditions is discussed.