EVOLUTIONARY HISTORY OF LORISIFORM PRIMATES

We integrate information from the fossil record, morphology, behavior and molecular studies to provide a current overview of lorisoid evolut ion. Several Eocene prosimians of the northern continents, including b oth omomyids and adapoids, have been suggested as possible lorisoid an cestors, but these cannot be substantiated as true strepsirhines. A sm all-bodied primate, Anchomomys, of the middle Eocene of Europe may be the best candidate among putative adapoids for status as a true streps irhine. Recent finds of Eocene primates in Africa have revealed new pr osimian taxa that are also viable contenders for strepsirhine status. Plesiopithecus terns is a Nycticeblu-sized, nocturnal prosimian from t he late Eocene, Fayum, Egypt, that shares cranial specializations with lorisoids, but it also retains primitive features (e.g., four premola rs) and has unique specializations of the anterior teeth excluding it from direct lorisi-form ancestry. Another unnamed Fayum primate resemb les modem cheirogaleids in dental structure and body size. Two genera from Oman, Omanodon and Shizarodon, also reveal a mix of similarities to both cheirogaleids and anchomomyin adapoids. Resolving the phylogen etic position of these Africa primates of the early Tertiary will sure ly require more and better fossils. By the early to middle Miocene, lo risoids were well established in East Africa, and the debate about whe ther these represent lorisines or galagines is reviewed. Neontological data are used to address the controversial branching sequences among extant lorisid clades. Data from the skin and scent glands, when integ rated with other lines of evidence, suggest that Asian and African lor isines share a common lorisine ancestry. The hypothesis of an African clade containing both pottos and galagos to the exclusion of Asian lor isines is less tenable. True galagines are found in the fossil record of Namibia, while true lorisines are known from the Miocene of Asia. T he hypothetical branching sequences can be integrated with behavioral and morphological features to develop an adaptive model of lorisoid di vergence. By specializing on two different foraging modes early in the ir radiation, lorisines and galagines subsequently underwent a chain o f integrated evolutionary changes eventually having an impact on many components of locomotor behavior, anatomy, physiology, reproduction li fe history, and social behavior. Ongoing evolutionary studies of extan t galagines are illuminating population phenomena and processes of spe ciation in an ecological context.