Koobi Fora Research Project , Volume 6 : The Fossil Monkeys

A cercopithecoid primates first evolved in the latter part of the Miocene epoch, it was not until the Plio-Pleistocene when the two subfamilies of Old World monkeys, the colobinae and cercopithecinae, started to morphologically and ecologically diversify. This diversification is well documented in the primate fossil record, especially in the Koobi Fora Formation. In The Fossil Monkeys, which is edited by N. Jablonski and M. Leakey, the reader is provided with comprehensive anatomical descriptions of fossil cercopithecoids from the Plio-Pleistocene and is introduced to some interpretations of cercopithecoid evolution and paleobiology (e.g., diet). This volume centers around the >890 recovered fossil specimens that can be confidently assigned to eight genera and possibly more than 11 species of cercopithecoids; there are even more specimens that are clearly cercopithecoid but lack distinctive taxonomic affinities. Although the fossil hominins from the Koobi Fora Formation traditionally receive more attention (e.g., Spoor et al. 2007), hominins are only represented by a sample of just over 200 specimens, thus demonstrating that the cercopithecoids may have been the dominant primate fauna at this time in East Africa. The first four chapters of The Fossil Monkeys include an Introduction (Chapter I) in which all measurements obtained from skulls, teeth, and postcranial elements are outlined, and the systematic paleontology (Chapters II–IV) of the fossil cercopithecoids recovered up to and including the 2004 field season. In addition to the descriptive anatomy, the systematic paleontology chapters are complemented by 1) exceptional photographs of some of the better-preserved specimens, often in multiple views, and, 2) detailed tables that include lists of specimens (by provenience and taxon) and their measurements. The Appendix at the end of the printed volume also provides a comprehensive table of measurements for each specimen, and the supplementary DVD (which can be purchased separately from the hardcover book) includes additional color photographs of specimens not illustrated in the printed text, and a searchable PDF file of the entire printed volume. Chapter II, by N. Jablonski and M. Leakey, primarily focuses on descriptions of a new small colobine species from Koobi Fora, Colobus freedmani. Despite few cranial fragments, several mandibles, isolated teeth, and postcranials from both foreand hind limbs are abundant, including a partial skeleton of a probable female, KNM-ER 5896. These authors conclude that C. freedmani was very similar to living Colobus, except that it may have been slightly larger (estimated mass of 11 kg) and that it may represent one of the first examples of a colobus monkey of modern aspect in the primate fossil record. Chapter III, by N. Jablonski, M. Leakey, C. Ward and M. Antón, describes fossil material from previously named “large” colobine monkeys: Rhinocolobus turkanaensis, Cercopithecoides williamsi, Cercopithecoides kimeui, and Paracolobus mutiwa. Chapter IV, also by N. Jablonski, M. Leakey, and M. Antón, is dominated by numerous descriptions of Theropithecus material, but it also describes the few recovered, but still very important fossil guenons (Cercopithecus), mangabeys (Lophocebus), and generalized baboons (Parapapio). Interestingly, these authors suggest that some of the larger morphs of Parapapio may possibly be related to Mandrillus, a monkey genus that has virtually no fossil record. There is a wealth of anatomical detail in these two chapters, however, considering that previous descriptions of some of this material had been previously published when these taxa were first described, there is very little new information about the biology of these animals (e.g., body size estimates, inferences about locomotor behaviors; see Delson et al. 2000). For example, the new fossil descriptions from the expanded Koobi Fora collections reconfirm that Rhinocolobus was likely more arboreal than Cercopithecoides, and that Theropithecus species were extremely variable in its morphology, ecology and behavior. Although the anatomical descriptions comprise the bulk of Chapters II–IV, the beautiful (and colorful) full body reconstruction created by Mauricio Antón included in Chapters III and IV provide nice visuals of these extinct monkeys. Rhinocolobus is depicted sitting on an arboreal support, while Cercopithecoides williamsi and Theropithecus oswaldi are both shown in a terrestrial stance. Each of these animals is represented by reconstructions of its bony skeleton, its muscular anatomy, and its skin and hair color. These illustrations are indeed a welcome addition to these description heavy chapters, as is the narrative of the rationale and methodology used in creating the reconstructions. Chapter V, by N. Jablonski and G. Chaplin, comes directly after the systematic paleontology section of this volume and provides what the authors refer to as “natural language descriptions” of the fossil monkeys. Using 151 unordered and ordered multistate characters, Jablonski and Chaplin employ the DELTA (DEscription Language for TAxonomy) system (Dallwitz et al. 2000) to create a flow chart that is supposed to facilitate the identification of fossil monkeys to a given species. The authors also provide a