Late Miocene micromammals from the Lukeino Formation (6.1 to 5.8 Ma), Kenya

Abstract

Micromammalian fossils have been recovered at several localities (Aragai, Kapsomin and Kapcheberek) in Late Miocene sediments of the Lukeino Formation, eastern foothills of the Tugen Hills, Kenya. The deposits range in age from 6.1 to 5.8 Ma. This paper includes over 800 specimens (897 teeth, not counting numerous rodent incisors), mostly isolated cheek teeth, but several mandibles and maxillae as well. The assemblage is dominated by four species, a late surviving phiomyid Apodecter (144 specimens), an early form of Abudhabia (114 specimens), a new genus of murid (124 specimens) and a primitive species of Saidomys (326 specimens (393 cheek teeth). Saccostomus is represented by 16 teeth, and dendromurines are quite common (31 specimens). The leporid Serengetilagus is also reasonably abundant (24 specimens), the remainder of the taxa being represented by fewer than 10 specimens each. Remains of the early hominid, Orrorin tugenensis, has been found in intimate association with the microfauna which can thus be used to reconstruct the palaeoenvironment of the earliest known bipeds. The presence of galagids, fruit bats and the diversity of dendromurines (3 species) and some probably arboreal murids (possibly ancestral to Thallomys or Grammomys ) indicates the presence of trees in the vicinity of the site, but some of the taxa suggest the presence of relatively open environments in the vicinity of Kapsomin at the time of deposition. A similar mixture of vegetation types is indicated by the large mammals from Lukeino.