The Cleveland Museum of Natural History

A small sample of hyracoid fossils from the late Miocene (,6.1 Ma) deposits at Lemudong’o, Narok, Kenya, belong to Dendrohyrax. This genus was unknown in the fossil record until recently, when almost simultaneously it was discovered at Lukeino (6 Ma) and Lemudong’o, both in Kenya. The fossils from Lemudong’o belong to a small species of the genus, not very different from Dendrohyrax validus. The Lukeino specimens are larger, and have been attributed to a new species Dendrohyrax samueli. The presence of tree hyraxes at these sites is indicative of forest at the time of deposition of the strata. Introduction Lemudong’o Locality 1 is a late Miocene (,6.1 Ma) mammalian-dominated fossil locality within the Narok District of Kenya (Ambrose et al., 2003; Ambrose, Bell, et al., 2007; Ambrose, Kyule, and Hlusko, 2007; Ambrose, Nyamai, et al., 2007; Deino and Ambrose, 2007). The primary fossil assemblage derives from the mudstone horizon and is dominated by specimens attributed to Bovidae and Cercopithecidae. However, the Hyracoidea are the third most commonly found taxon, comprising approximately 9% of the collection (112 specimens) (Ambrose, Bell, et al., 2007). This large proportion of the total mammalian assemblage is rare among Miocene and Plio-Pleistocene fossil localities in eastern and southern Kenya, and provides an uncommon insight into the paleoecology of this region. All extant members of the Hyracoidea are classified within the family Procaviidae. The living Procaviidae are classified into two or three genera, depending on which authority one reads. All researchers are agreed that Procavia is distinct from the Heterohyrax/Dendrohyrax pair, but it is the relationship between the latter two that is subject to debate, with some researchers, such as Ellerman and Morrison-Scott (1951), Roche (1972) , and Hoeck (1978), classifying Heterohyrax as a subgenus of Dendrohyrax, and others (Hahn, 1934; Bothma, 1967, 1971; Skinner and Smithers, 1990, p. 553–563; Rasmussen et al., 1996) accepting that they represent distinct genera. Even though their dentitions are similar to each other in many ways, the cranial morphology, reproductive biology, life history variables, territoriality and vocalization reveal that they represent two separate genera, the view accepted here. Fossil Procaviidae are known from many Plio-Pleistocene localities in East and South Africa (Churcher, 1956; Kitching, 1965; Jaeger and Wesselman, 1976; McMahon and Thackeray, 1994; Schwartz, 1997), but Miocene occurrences are rare, the only ones known prior to publication of this paper being from Namibia (Rasmussen et al., 1996) and Kenya (Fischer, 1986). In both the latter occurrences, the procaviids were identified as Heterohyrax. Procaviids have recently been collected at two late Miocene sites in Kenya, Lukeino in the Tugen Hills (Pickford, 2005), and Lemudong’o, near Narok. At Lukeino, the Aragai palate is complete enough to reveal that it belongs to a new species of Dendrohyrax, D. samueli (Pickford, 2005). The Lemudong’o fossils in contrast are fragmentary and many of the features that are diagnostic for identifying Heterohyrax and Dendrohyrax are lacking. However, the base of a symphysis preserves morphology that is usually only found in Dendrohyrax (presence of roughened ridges separated from the body of the symphysis by grooves), and the ectoloph morphology of the upper molars suggests the same identification. The dental remains from Lemudong’o plot within the ranges of metric variation of both Dendrohyrax and Heterohyrax. If they are Heterohyrax then they represent a large species of the genus, but if they are attributed to Dendrohyrax, then they would denote a small species of the genus. The assumption is that only one genus is present at the site, and, if so, then it is a Dendrohyrax close in size to D. validus.