Journal of Human Evolution xxx (xxxx) xxx Contents lists available at ScienceDirect Journal of Human Evolution journal homepage: www.elsevier.com/locate/jhevol A diminutive Pliocene guenon from Kanapoi, West Turkana, Kenya * J. Michael Plavcan a, , Carol V. Ward b, Richard F. Kay c, Fredrick K. Manthi d a Department of Anthropology, University of Arkansas, Fayetteville, AR, 72701, USA b Department of Pathology and Anatomical Sciences, M263 Medical Sciences Building, University of Missouri, Columbia, MO, 65212, USA c Department of Evolutionary Anthropology and Division of Earth and Ocean Sciences, Duke University, Box 90383, Durham, NC, 27708, USA d Department of Earth Sciences, National Museums of Kenya, P.O. Box 40658, Nairobi, Kenya article info abstract Article history: Although modern guenons are diverse and abundant in Africa, the fossil record of this group is sur- Received 15 May 2018 prisingly sparse. In 2012 the West Turkana Paleo Project team recovered two associated molar teeth of a Accepted 22 May 2019 small primate from the Pliocene site of Kanapoi, West Turkana, Kenya. The teeth are bilophodont and the Available online xxx third molar lacks a hypoconulid, which is diagnostic for Cercopithecini. The teeth are the same size as those of extant Miopithecus, which is thought to be a dwarfed guenon, as well as a partial mandible Keywords: preserving two worn teeth, previously recovered from Koobi Fora, Kenya, which was also tentatively Miopithecus identified as a guenon possibly allied with Miopithecus. Tooth size and proportions, as well as analysis of Nanopithecus Cercopithecini relative cusp size and shearing crest development clearly separate the fossil from all known guenons. Dwarfing Based on the Kanapoi material, we erect a new genus and species, Nanopithecus browni gen. et sp. nov. The small size of the specimen suggests either that dwarfing occurred early in the lineage, or at least twice independently, depending on the relationship of the new species with extant Miopithecus. Further, the distinctive habitat and geographic separation from Miopithecus suggests that the origin of small body size is not uniquely linked to the current habitat of Miopithecus, and possibly that relatives of extant Miopithecus were much more widely distributed in the past. This in turn argues caution in using extant biogeography in models of the origins of at least some guenons. © 2019 Elsevier Ltd. All rights reserved. 1. Introduction the radiation of modern guenons, the group is thought to be African in origin, and the modern distribution of most extant species is The modern guenons (Cercopithecini) comprise a widespread thought to reflect a series of vicariance events related to patterns of radiation of African primates including up to six genera (Eryth- habitat fragmentation associated with climate change beginning in rocebus, Allenopithecus, Chlorocebus, Allochrocebus, Miopithecus and the late Miocene (Kingdon, 1971; Kamilar et al., 2009; Hart et al., Cercopithecus; Pozzi et al., 2014; Lo Bianco et al., 2017) with more 2012; Lo Bianco et al., 2017). than 30 species that inhabit diverse habitats throughout sub- Though molecular studies have helped clarify the phylogenetic Saharan Africa. Recent molecular studies place the origin of the relationships among guenon genera and provide strong evidence of guenons at approximately 10e12 Ma. Most studies recognize Alle- the antiquity of the group, the fossil record of guenons remains nopithecus as the sister taxon to the remaining guenons with the comparatively poor. Unfortunately, identification of fossil speci- divergence at approximately at 8e10 Ma (supporting Strasser and mens to species is hampered by morphological near uniformity of Delson, 1987). Miopithecus is placed as the sister taxon to either cercopithecine molar teeth. Most guenon fossils are known from the arboreal guenons (Cercopithecus), or both the arboreal and East African deposits dated to 0.6 Ma and younger and are attrib- terrestrial (Erythrocebus, Allochrocebus, and Chlorocebus) guenons, uted to Chlorocebus sp. indet. or Erythrocebus patas (see Jablonski with a split at approximately 7e8Ma(Tosi et al., 2004, 2005; Hart and Frost, 2010). Specimens from Omo, dated to 2.9 Ma, have et al., 2012; Perelman et al., 2011; Springer et al., 2012; Pozzi et al., been attributed to Cercopithecus sp. (Eck and Howell, 1972). A single 2014). Though little is understood about the evolutionary history of fragmentary mandible from Kanam (Kenya) and isolated teeth from Olduvai (Tanzania), and Loboi (Kenya; Szalay and Delson, 1979; Harrison and Harris, 1996; Jablonski and Frost, 2010), and a hori- * Corresponding author. zon of uncertain age at Taung have also been referred to this group E-mail address: [email protected] (J.M. Plavcan). https://doi.org/10.1016/j.jhevol.2019.05.011 0047-2484/© 2019 Elsevier Ltd. All rights reserved. Please cite this article as: Plavcan, J.M et al., A diminutive Pliocene guenon from Kanapoi, West Turkana, Kenya, Journal of Human Evolution, https://doi.org/10.1016/j.jhevol.2019.05.011 2 J.M. Plavcan et al. / Journal of Human Evolution xxx (xxxx) xxx (Szalay and Delson, 1979; Broadfield et al., 1994). The oldest known derive from the paleosol upon which they were recovered. The guenon fossil is an isolated tooth from the United Arab Emirates proximity of the specimens, the preservation, and the morphology dated to 6.5e8.0 Ma, referred only to Cercopithecini indet. (Gilbert all strongly suggest that the teeth came from a single individual. et al., 2014). This specimen is reported as similar in tooth size to a Subsequent dry sieving of the surrounding matrix failed to recover modern vervet or blue monkey, which falls comfortably within the additional material. size range of most living guenons (approximately 3e9 kg average adult body mass) with the exception of the largest, Erythrocebus (average male mass 12.4 kg) and smallest, Miopithecus (average 3. Materials and methods female mass 1.1 kg; Smith and Jungers, 1997; Delson et al., 2000). One fossil specimen from Koobi Fora, Kenya, has been suggested Comparative dental metric data (Table 1; complete data in to have affinities with extant Miopithecus (Jablonski et al., 2008). Supplemental Online Material [SOM] Table S1) comprising stan- KNM-ER 396, a mandibular fragment with worn M2eM3, has been dard mesiodistal and buccolingual tooth dimensions for extant noted as a possible relative of the modern talapoin (Miopithecus)on primates were taken from Plavcan (1990). These include data from the basis of tooth size, even though Jablonski et al. (2008) only extant species of Miopithecus: Miopithecus talapoin (Schreber, 1774) tentatively referred the specimen to Cercopithecus species indet. B. from Angola, and Miopithecus ogouensis (Kingdon, 1997) from Notably, Miopithecus is not only the smallest living catarrhine Cameroon and Gabon. Tooth size measurements of KNM-KP 53150 primate, but it is also thought to be phyletically dwarfed (Strasser and KNM-ER 396 were taken using a microscope with calibrated and Delson, 1987; Shea, 1992). The presence of Miopithecus in the measurement software at the National Museums of Kenya. Tooth early Pliocene would suggest that dwarfing occurred early in this size data for NME L621-4A, the smallest guenon from Omo Shun- lineage (Jablonski et al., 2008; Lo Bianco et al., 2017). Further, as gura, Ethiopia, dated to 2.9 Ma (Eck and Howell, 1972), were taken modern talapoins are confined to dense tropical forest in west using calipers on the original specimen. Tooth size data were ln- central Africa while the Turkana Basin was characterized by dry transformed before analysis. Ln-transformed tooth dimensions woodlands and savannas (Bobe, 2011), the finding of a guenon were compared graphically to those of extant guenons, and a closely related or ancestral to Miopithecus would have significant principal components analysis (PCA) of the ln-transformed tooth biogeographic and ecological implications for the evolution of this dimension data was run in SYSTAT v. 13 (Systat Software, San Jose, genus and possibly for the evolution of guenons as a group (Lo CA) using a variance-covariance matrix. Bianco et al., 2017). Unfortunately, the KNM-ER 396 teeth are Shearing crest data for KNM-KP 53150 were measured by R.F.K. heavily worn, precluding anything other than its identification as a using high fidelity epoxy casts of the specimens. Shearing crest data guenon that is similar in tooth size to modern talapoins. were not taken for KNM-ER 396 because the specimen is too worn. Fieldwork at the Pliocene site of Kanapoi, Kenya, was renewed in Eight crest lengths and two cusp heights were measured on the M2 2012 by the West Turkana Paleo Project. Surface prospecting at the of samples of M. talapoin (n ¼ 4), M. ogouensis (n ¼ 19) and the new type locality of Australopithecus anamensis (‘Nzube's Mandible Site’; taxon erected here (Table 2). A description of the measurements is Leakey et al., 1995) recovered two isolated mandibular teeth. The found in Kay (1978). Because the specimens being compared are specimens are very small, and morphologically resemble the living similar in size, we expressed each shearing crest length and cusp West African talapoin, Miopithecus. If related to Miopithecus, these height as a ratio of the measurement to mesiodistal molar length, specimens would either confirm the presence of a close relative to following Kay (1978). We employ PCA to compare M. talapoin, modern talapoins at almost 4.2 Ma in East Africa, or imply that M. ogouensis, and the described specimen on the basis of these small body size was achieved at least twice among Cercopithecini. measurements. Additionally, species means of size-adjusted Here we describe these new specimens and discuss their relevance shearing data from Kay (1978) for a series of guenons as well as to understanding the evolution of guenons. Lophocebus albigena were compared to that for KNM-KP 53150 using PCA (Table 3). These analyses were conducted in SYSTAT 13 v. 2.