New Fauna from Loperot Contributes to the Understanding of Early Miocene Catarrhine Communities

The site of Loperot in West Turkana, Kenya, is usually assigned to the Early Miocene. Recent discoveries at Loperot, including catarrhine primates, led to a revision of its mammalian fauna. Our revision of the fauna at Loperot shows an unusual taxonomic composition of the catarrhine community as well as several other unique mammalian taxa. Loperot shares two non-cercopithecoid catarrhine taxa with Early Miocene sites near Lake Victoria, e.g., Songhor and the Hiwegi Formation of Rusinga Island, but Loperot shares a cercopithecoid, Noropithecus, with Buluk (Surgei Plateau, near Lake Chew Bahir). We use Simpson’s Faunal Resemblance Index (Simpson’s FRI), a cluster analysis, and two partial Mantel tests, to compare Loperot to 10 other localities in East Africa representing several time divisions within the Early and Middle Miocene. Simpson’s FRI of mammalian communities indicates that Loperot is most similar in its taxonomic composition to the Hiwegi Formation of Rusinga Island, suggesting a similarity in age (≥18 Ma) that implies that Loperot is geographically distant from its contemporaries, i.e., Hiwegi Formation of Rusinga Island, Koru, Songhor, and Napak, while at the same time older than other sites in West Turkana (Kalodirr and Moruorot). The cluster analysis of the similarity indices of all the localities separates Loperot from other Early Miocene sites in the study. Two partial Mantel tests show that both temporal distance and geographic distance between sites significantly influence similarity of the mammalian community among sites. Thus, Loperot’s unique location in space and time may explain why it has an unusual catarrhine community and a number of unique taxa not seen elsewhere.