The purpose of this communication is to describe and provide a preliminary interpretation of a hominoid proximal humeral fragment recovered from sediments more than 4.0 m.y. old in the Baringo District, Kenya. The geological and chronological context of the fossil is examined and associated fauna is analyzed.
In 1973, one of us (M.P.) studied the sedimentary succession west of Lake Baringo, Kenya. Vertebrate fossils were collected from sediments mapped as Chemeron Formation (Northern Extension) during the course of the survey Pickford, 1975). Locality 21210 (Mabaget) yielded a surfacecollected assemblage of fossils typical of the unit, including a proximal humeral fragment of a large primate (KNM-BC 1745)l. Field identification of the specimen as "hominid" was later rejeded in the laboratory because of its small size and thick shaft cortex.
In 1980, the senior author happened to examine casts of the humeri of "Lucy", A.L.
288-1 from Hadar, Ethiopia. A few days later, upon m a t i n g the previous collections from Baringo, the proximal humerus from Loc. 2/ 210 passed through his hands and was "rediscovered". Direct comparisons with the humeri of A.L. 288-1 codirmed that the two are morphologically similar, although the Ba-ring0 specimen is marginally larger.
'KNM=Kenya National Museums; BC=Bmingo Chemeron.