Lorisine Primate from the Late Miocene of Kenya

Abstract

The origin of African Lorisidae has been the subject of debate for the past half century, so far without resolution. The matter is complecated by the fact that strepsirrhines (Lorisiformes = Lorisidae + Galagidae) are rare in the African fossil record, with large gaps between occurrences in the Early Oligocene Fayum (Egypy) deposit, the Early Miocene strata of East Africa and the Plio-Pleistocene of the same region. Likewise, the Asian fossil record of this group is spotty, with only a few specimens described from the Late Miocene of Pakistan. In the search for evidence concerning the dichotomy between Lorisidae and Galagidae, authors have tended to focus on the Early Miocene fossils from Kenya and Uganda which is the only region to have yielded a reasonable diversity of forms. Unfortunately, the history of study has been marred by the description and interpretation of non-primate material as strepsirrhines (Lorisiformes spurii). This contrasts with the genuine strepsirrhine (Lorisiformes veri) fossil from the same region which have thrown much light on the group, but which have not yet resolved the issue of the timing or the modality of the dichotomy between the two families. At present, among the described African fossil lorisiformes only the genus Mioeuoticus is accepted by some, but not all, authors (Harrison, 2010) as a Lorisidae (or Lorisinae, all the others generally being classed as Galagidae (or Galginae) Walker (1987). It is thus of interest to put on record the discovery of a lorisid anout from the Late Miocene deposits of the Tugen Hills, Kenya, which is close in dimensions and some aspects of the Far East (Nycticebus, Nycticeboides) and West Africa (Arctocebus). The fossil does not particularly resemble any of the Early Miocene forms described from East Africa, and it is suggested that the lineage entered Africa during the Late Miocene at the same time that several other vertebrate groups spread into the continent from South-East Asia.