Hipparions from the late Miocene and Pliocene of Northwestern Kenya

The faunas of Lothagam, Kanapoi and Ekora on the west side of Lake Rudolf in Kenya include well-preserved Hipparion material. The most interesting species is represented by a skull from Lothagam that is devoid of a preorbital fossa : Hipparion turkanense Hooijer & Maglio. The upper cheek teeth have small fossette plications and rather wrinkled anteroposterior fossette borders; the lower cheek teeth also show this wrinkled enamel condition, notably on the buccal wall, and sport no ectostylids. The closest resemblances are with certain Chinese "Pontian" forms described by Sefve. An equally large Hipparion with a preorbital fossa occurs at Kanapoi and Ekora. The upper cheek teeth are richly plicated fore and aft, and the anteroposterior fossette borders are not wrinkled. The lower cheek teeth do possess ectostylids, although these structures do not always show. This species also occurs in the "Pontian" of North Africa: it was described as Hipparion africanum Arambourg from Wad el Hammam in Algeria. We designate the Kanapoi-Ekora Hipparion as Hipparion primigenium (Von Meyer). A third species represented in the Lothagam-Kanapoi-Ekora collection is of small size; not only the teeth are present but also a set of metacarpals. The isolated teeth present a striking resemblance to those of Hipparion sitifense Pomel from deposits of pre-Villafranchian age in North Africa (Saint-Arnaud, Mascara). The median metacarpal is as slender in build as that of Hipparion mediterraneum Roth & Wagner from Pikermi, but the distal articulations of metacarpals II and IV are heavier than in that species. We designate the small northwestern Kenya Hipparion as Hipparion cf. sitifense Pomel.