Papers by Christopher Gilbert
Miocene to Pleistocene fossiliferous sediments in the Tugen Hills span the time period from at le... more Miocene to Pleistocene fossiliferous sediments in the Tugen Hills span the time period from at least 15.5 Ma to 0.25 Ma, including time periods unknown or little known elsewhere in Africa. Consequently, the Tugen Hills deposits hold the potential to inform us about crucial phylogenetic events in African faunal evolution and about long-term environmental change. Among the specimens collected from this region are a number of discoveries already important to the understanding of primate evolution. Here, we describe additional cercopithecoid material from the Miocene deposits in the Tugen Hills sequence, including those from securely dated sites in the Muruyur Beds (16e13.4 Ma), the Mpesida Beds (7e6.2 Ma) and the Lukeino Formation (w6.2e5.7 Ma). We also evaluate previously described material from the Ngorora Formation (13e8.8 Ma). Identified taxa include Victoriapithecidae gen. et sp. indet., cf. Parapapio lothagamensis, and at least two colobines. Specimens attributed to cf. Pp. lothagamensis would extend the species' geographic range beyond its type locality. In addition, we describe specimens sharing derived characters with modern African colobines (Tribe: Colobina), a finding that is congruent with previous molecular estimates of colobine divergence dates. These colobine specimens represent some of the earliest known members of the modern African colobine radiation and, in contrast to previous hypotheses, suggest that early African colobines were mainly arboreal and that semi-terrestrial Late Miocene and Plio-Pleistocene colobine taxa were secondarily derived in their locomotor adaptations.
Recently, we described ~12.5 million year old fossil colobine teeth from the Tugen Hills, Kenya. ... more Recently, we described ~12.5 million year old fossil colobine teeth from the Tugen Hills, Kenya. These specimens represent the earliest colobine and the earliest cercopithecid specimens in the fossil record by ~3 million years. In addition, recent expeditions to the Baynunah Formation, Emirate of Abu Dhabi, UAE, have resulted in the recovery of a fossil tooth representing the earliest known member of the tribe Cercopithecini (guenons), and the only guenon known outside of Africa. This new specimen is presented here, and it is currently the earliest cercopithecine monkey yet known outside of the African continent. The late Miocene fauna of Abu Dhabi is a unique blend that includes both African and Eurasian elements at this time, suggesting that the Arabian Peninsula was an important dispersal and exchange route for various mammalian lineages. The presence of early cercopithecines, and cercopithecins, in particular, on the Arabian Peninsula during the late Miocene provides important i...
The fossil colobine genus Cercopithecoides is temporally, geographically, and morphologically div... more The fossil colobine genus Cercopithecoides is temporally, geographically, and morphologically diverse. There are currently six species recognized from Late Miocene to Pleistocene sites in Africa with a possible seventh form present at Kromdraai B and Swartkrans in South Africa, for which the name C. coronatus (Freedman, 1957) is available. We focus on the cranial morphology of C. “coronatus” to both evaluate its affinities with other Cercopithecoides species and assess whether the observed differences are sufficient to warrant separate taxonomic status. Three-dimensional cranial landmarks, linear measurements, and dental metrics were taken on 294 crania, 422 upper and 565 lower molars of extant and fossil colobines. The C. “coronatus” crania are most similar in shape, size, and molar size to C. kimeui. Most species of Cercopithecoides share a similar molar size to cranial size ratio, although C. haasgati specimens stand out for having large teeth relative to their cranial size. Prin...
Fig. S1. CT Scans of AUH 1321. Clockwise from Top Left: mesial, occlusal, distal, oblique root, b... more Fig. S1. CT Scans of AUH 1321. Clockwise from Top Left: mesial, occlusal, distal, oblique root, buccal, and lingual views. Note that the distal root of AUH 1321 appears either broken or slightly open at its distal apex, indicating it would have been longer than preserved. The irregularity of the opening combined with the moderate wear of the tooth suggests a small amount of breakage rather than a slightly open apex. Gilbert et al. www.pnas.org/cgi/content/short/1323888111
The taxonomy of the fossil colobine genus Cercopithecoides has been debated by paleoprimatologist... more The taxonomy of the fossil colobine genus Cercopithecoides has been debated by paleoprimatologists for decades. Currently, six species of Cercopithecoides are recognized in the Late Miocene to Plio-Pleistocene of South and East Africa. C. williamsi, found at Koobi Fora, Leba, Makapansgat, Sterkfontein, Swartkrans, Bolt’s Farm, and Kromdraai, is one of only two Cercopithecoides species recognized in South Africa. Material from Kromdraai B (KB) and Swartkrans (SK), however, has previously been noted to be larger than that from Sterkfontein, Makapansgat, and Bolt's Farm. This analysis examines the status of these larger specimens relative to other C. williamsi populations and other recognized Cercopithecoides taxa. To assess the taxonomic affinities of the various C. williamsi populations, the size and shape of Cercopithecoides molars were compared to a sample of 407 upper and 529 lower molars of extant and fossil colobines. The KB and SK material generally overlaps the largest Cer...
Evolutionary Anthropology Issues News and Reviews
American journal of physical anthropology, Jan 29, 2015
The African papionin primates commonly known as mangabeys form a diphyletic group with white-eyel... more The African papionin primates commonly known as mangabeys form a diphyletic group with white-eyelid mangabeys (Cercocebus) being most closely related to drills and mandrills (Mandrillus). However, the phylogenetic relationships among members of the Cercocebus-Mandrillus clade have not been investigated in detail, particularly from a morphological perspective. Early studies of white-eyelid mangabeys considered C. agilis to best represent the ancestral lineage and C. torquatus as the most derived species, the result of multiple biogeographic dispersal events. More recently, a sister-clade relationship between Mandrillus and either C. chrysogaster or C. torquatus has been proposed. Here we present the results of phylogenetic analyses based on 206 craniodental characters (103 representing males and females separately) of four species of Cercocebus and both species of Mandrillus. When all species of the Cercocebus-Mandrillus clade are analyzed without molecular constraints, results sugge...
PLOS ONE, 2015
Thumb reduction is among the most important features distinguishing the African and Asian colobin... more Thumb reduction is among the most important features distinguishing the African and Asian colobines from each other and from other Old World monkeys. In this study we demonstrate that the partial skeleton KNM-ER 4420 from Koobi Fora, Kenya, dated to 1.9 Ma and assigned to the Plio-Pleistocene colobine species Cercopithecoides williamsi, shows marked reduction of its first metacarpal relative to the medial metacarpals. Thus, KNM-ER 4420 is the first documented occurrence of cercopithecid pollical reduction in the fossil record. In the size of its first metacarpal relative to the medial metacarpals, C. williamsi is similar to extant African colobines, but different from cercopithecines, extant Asian colobines and the Late Miocene colobines Microcolobus and Mesopithecus. This feature clearly links the genus Cercopithecoides with the extant African colobine clade and makes it the first definitive African colobine in the fossil record. The postcranial adaptations to terrestriality in Cercopithecoides are most likely secondary, while ancestral colobinans (and colobines) were arboreal. Finally, the absence of any evidence for pollical reduction in Mesopithecus implies either independent thumb reduction in African and Asian colobines or multiple colobine dispersal events out of Africa. Based on the available evidence, we consider the first scenario more likely.
Over the past century, numerous specimens collected near Ramnagar (Jammu and Kashmir Province, In... more Over the past century, numerous specimens collected near Ramnagar (Jammu and Kashmir Province, India) have proven important in understanding the evolution and biogeography of many mammalian groups, including hominoid apes. The precise geochronology of the Ramnagar-area deposits, however, remains uncertain and is an active topic of research. Since 2010 we have renewed fossil prospecting in the Lower Siwalik deposits near Ramnagar in an attempt to better understand the evolution, biogeographic timing, and paleoclimatic context of mammalian radiations in Asia. Our explorations have resulted in the identification of at least two new fossil bearing localities, as well as the probable relocation of a purported 15-18 Ma hominoid locality near Ramchand Ridge. In this paper, we present the preliminary results of our collection efforts along with our current biochronological estimate of the Ramnagar-area deposits. Recovered fauna includes typical Chinji taxa such as rodents, tragulids, bovids...
Palaeobiodiversity and Palaeoenvironments, 2015
Your article is protected by copyright and all rights are held exclusively by Senckenberg Gesells... more Your article is protected by copyright and all rights are held exclusively by Senckenberg Gesellschaft für Naturforschung and Springer-Verlag Berlin Heidelberg. This e-offprint is for personal use only and shall not be selfarchived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com".
Proceedings of the National Academy of Sciences of the United States of America, Jan 15, 2014
A newly discovered fossil monkey (AUH 1321) from the Baynunah Formation, Emirate of Abu Dhabi, Un... more A newly discovered fossil monkey (AUH 1321) from the Baynunah Formation, Emirate of Abu Dhabi, United Arab Emirates, is important in a number of distinct ways. At ∼ 6.5-8.0 Ma, it represents the earliest known member of the primate subfamily Cercopithecinae found outside of Africa, and it may also be the earliest cercopithecine in the fossil record. In addition, the fossil appears to represent the earliest member of the cercopithecine tribe Cercopithecini (guenons) to be found anywhere, adding between 2 and 3.5 million y (∼ 50-70%) to the previous first-appearance datum of the crown guenon clade. It is the only guenon--fossil or extant--known outside the continent of Africa, and it is only the second fossil monkey specimen so far found in the whole of Arabia. This discovery suggests that identifiable crown guenons extend back into the Miocene epoch, thereby refuting hypotheses that they are a recent radiation first appearing in the Pliocene or Pleistocene. Finally, the new monkey is...
Developments in Primatology: Progress and Prospects, 2008
Developments in Primatology: Progress and Prospects, 2008
... 1 1961/62: From left to right, Frans Sami Faheem, Abu Hassan Ali Issa, Donald E. Russell, Ibr... more ... 1 1961/62: From left to right, Frans Sami Faheem, Abu Hassan Ali Issa, Donald E. Russell, Ibrahim, unidentified, Mahmood Bishir ... Kwame Said, Hassan Ali, ''Sammy'' Issa Zakri, Ellen Miller; Middle Row: Mohammed Daood, Said Hashem, Ali Barakat, Abdel Latif, David Froehlich ...
The Quarterly Review of Biology, 2012
Proceedings of the National Academy of Sciences, 2007
There are many cases of incongruence between phylogenetic hypotheses produced from morphological ... more There are many cases of incongruence between phylogenetic hypotheses produced from morphological data and those produced from molecular data. In such instances, many researchers prefer to accept the results of molecular phylogenies. For example, in a recent analysis of primate phylogenies based on craniodental characters, Collard and Wood [Collard M, Wood BA (2000) Proc Natl Acad Sci USA 97:5003-5006] argued that, because craniodental data do not yield relationships concordant with molecular studies, the results of studies that employ such characters must be considered suspect. As most of our knowledge of mammalian evolution and phylogenetic history comes from craniodental fossils, these results have dramatic implications. However, the aforementioned analysis did not take into account the potentially confounding effects of allometry on quantitative craniodental characters. In this article, we employ a previously undescribed narrow allometric coding method that accounts for such confounding influences in phylogenetic analyses of craniodental morphology. By using essentially the same raw data set as Collard and Wood [Collard M, Wood BA (2000) Proc Natl Acad Sci USA 97:5003-5006], 65 quantitative craniodental characters were adjusted in a parsimony analysis for the primate tribe Papionini, a group of monkeys argued to display extensive homoplasy. The resulting phylogenetic tree was congruent with the phylogenetic tree based on molecular data for these species, thereby meeting the ''criterion of congruence.'' These results suggest that morphological data, when treated properly, can be considered as reliable as molecular data in phylogenetic reconstruction. Rather than accepting phylogenetic hypotheses from one data source over another, cases of incongruence should be examined with greater scrutiny. narrow allometry ͉ character coding ͉ papionins ͉ cladistics ͉ phylogeny
Proceedings of the National Academy of Sciences, 2013
PLoS ONE, 2012
In June 2007, a previously undescribed monkey known locally as ''lesula'' was found in the forest... more In June 2007, a previously undescribed monkey known locally as ''lesula'' was found in the forests of the middle Lomami Basin in central Democratic Republic of Congo (DRC). We describe this new species as Cercopithecus lomamiensis sp. nov., and provide data on its distribution, morphology, genetics, ecology and behavior. C. lomamiensis is restricted to the lowland rain forests of central DRC between the middle Lomami and the upper Tshuapa Rivers. Morphological and molecular data confirm that C. lomamiensis is distinct from its nearest congener, C. hamlyni, from which it is separated geographically by both the Congo (Lualaba) and the Lomami Rivers. C. lomamiensis, like C. hamlyni, is semi-terrestrial with a diet containing terrestrial herbaceous vegetation. The discovery of C. lomamiensis highlights the biogeographic significance and importance for conservation of central Congo's interfluvial TL2 region, defined from the upper Tshuapa River through the Lomami Basin to the Congo (Lualaba) River. The TL2 region has been found to contain a high diversity of anthropoid primates including three forms, in addition to C. lomamiensis, that are endemic to the area. We recommend the common name, lesula, for this new species, as it is the vernacular name used over most of its known range.
Journal of Human Evolution, 2008
Journal of Human Evolution, 2007
The shape of the enamel-dentine junction (EDJ) in primate molars is regarded as a potential indic... more The shape of the enamel-dentine junction (EDJ) in primate molars is regarded as a potential indicator of phylogenetic relatedness because it may be morphologically more conservative than the outer enamel surface (OES), and it may preserve vestigial features (e.g., cuspules, accessory ridges, and remnants of cingula) that are not manifest at the OES. Qualitative accounts of dentine-horn morphology occasionally appear in character analyses, but little has been done to quantify EDJ shape in a broad taxonomic sample. In this study, we examine homologous planar sections of maxillary molars to investigate whether measurements describing EDJ morphology reliably group extant anthropoid taxa, and we extend this technique to a small sample of fossil catarrhine molars to assess the utility of these measurements in the classification of fossil teeth. Although certain aspects of the EDJ are variable within a taxon, a taxon-specific cross-sectional EDJ configuration predominates. A discriminant function analysis classified extant taxa successfully, suggesting that EDJ shape may a reliable indicator of phyletic affinity. When considered in conjunction with aspects of molar morphology, such as developmental features and enamel thickness, EDJ shape may be a useful tool for the taxonomic assessment of fossil molars.
Journal of Human Evolution, 2007
Previous studies have noted skeletal and dental differences supporting the diphyletic origin of t... more Previous studies have noted skeletal and dental differences supporting the diphyletic origin of the mangabeys. Documented postcranial and dental characters are congruent with molecular data and thus support a close relationship between Cercocebus and Mandrillus (mandrills and drills) on the one hand and Lophocebus, Papio (baboons), and Theropithecus (geladas) on the other. Most of these characters, however, are postcranial and difficult to assess in the papionin fossil record because associated material is rare. In order to assess the African papionin fossil record and determine the evolutionary history of this group, cranial characters are critical. Here, a set of craniomandibular morphologies are documented that support the diphyletic origin of the mangabeys and more broadly support the molecular African papionin clades (i.e., Cercocebus/Mandrillus vs. Lophocebus/Papio/Theropithecus). These characters are then used to identify a series of fossil crania from Taung as representative of a new member of the Cercocebus/Mandrillus clade, Procercocebus antiquus. Procercocebus antiquus is closest in morphology to the extant taxon Cercocebus torquatus, and a probable ancestor-descendant relationship between Procercocebus and Cercocebus is suggested. Paleoecological reconstructions also suggest that a predator-prey relationship between African crowned eagles and the Procercocebus-Cercocebus lineage has existed for approximately the last two million years. Implications for Cercocebus biogeography and evolution are discussed.
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Papers by Christopher Gilbert