Late Middle Pleistocene Elephants from Natodomeri, Kenya and the Disappearance of Elephas (Proboscidea, Mammalia) in Africa

Abstract

Comparative morphometric study of recently recovered fossil elephant molars from Natodomeri, Kenya identifies them as belonging to Elephas jolensis and confirms the presence of this species in Members I and II of the Kibish Formation. Improved datation of these geological units constrains them between 205 and 130 ka. Elephas jolensis is also reported from localities in northern, northwestern, eastern, and southern Africa. Thus, including its Natodomeri occurrence, E. jolensis appears to have been pan-African in distribution. Despite the wide geographic distribution of the species, molars of E. jolensis are remarkably uniform morphometrically. They are characterized by their extreme hypsodonty, high amplitude of enamel folding, high lamellar frequency, and plates that are anteroposteriorly thick relative to transverse valley interval spacing. In addition, they exhibit only a modest number of plates (<20 in M3/m3). Elephas jolensis either evolved from or represents the last stage of Elephas recki, the dominant elephant species in East Africa during the late Pliocene-Pleistocene. The dental morphology and isotopic composition of E. jolensis indicates that, like E. recki, it was a dedicated grazer. In the Kibish Formation, E. jolensis is succeeded by Loxodonta africana at 130 ka, coincident with an intensely cool, dry interval marked by episodes of extreme drought. This marked the extirpation of Elephas on the continent. The intensity and increased rate of climate fluctuation may have played an important role in the demise of the specialist, grazing E. recki-E. jolensis lineage in favor of a generalist, mixed feeder such as L. africana.