COMPARATIVE MORPHOMETRIC STUDY OF PROBOSCIDEAN DENTITION FROM THE APAK MEMBER OF THE NACHUKUI FORMATION AT LOTHAGAM, KENYA.

Abstract

The early Pliocene interval of the Apak Member at Lothagam, Kenya, documents significant faunal turnover. During this time, wooded savannas and savanna woodlands expanded in eastern Africa, and elephants consequently evolved to better adapt to grazing. It is also the time of the first appearance of the hominin Australopithecus, many modern antelope tribes, new horses, hippos, and pigs. Proboscidean species previously identified from the Apak Member include Deinotherium bozasi, Anancus kenyensis, Stegotetrabelodon orbus, cf. Elephas ekorensis? aff. Loxodonta, Loxodonta exoptata, and several unidentified elephantids. This study describes new proboscidean specimens and compiles a database of proboscideans from the Apak Member at Lothagam. The study focuses on measurements and morphological descriptions of 14 new and 12 previously studied specimens housed at the National Museums of Kenya. Essential features studied include relative height of the crown (hypsodonty index), which is important for grazing animals, and number of molar plates, which increase in more advanced proboscideans. The study further compares the new database, with that of late Miocene Lothagam proboscideans and proboscidean assemblages from nearby sites of similar age, particularly those from other sites in or near Turkana Basin including Kanapoi, Ileret, and South Turkwel. The objectives were to increase our knowledge of the transition from archaic to more advanced proboscideans in Africa and proboscidean cohorts' role in shaping ecosystem changes. The results meaningfully revise upwards, the taxonomic composition of proboscideans in the Apak Member, and reveal a complex relay of primitive to more derived elephants during the early Pliocene, that documents the adaptive response to increased competition among mammals for grazing resources