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Modern papionin monkeys are a diverse group that encompasses a broad range of morphologies, behaviors, and ecologies. A fossil genus known from African Plio-Pleistocene deposits, Parapapio, is widely regarded as a candidate ancestor to later African papionins. However, despite general agreement that this genus sits at or near the base of the African papionin clade, the taxonomy within Parapapio remains highly contentious. This project evaluates the species-level taxonomy of Parapapio with an explicit hypothesis-based approach to interpreting morphological variation in this sample of fossils. We tested two hypotheses: (H₁) the craniodental variation within Parapapio does not cluster into three groups that reflect the three known species, and (H₂) all the Parapapio fossils can be accommodated within the craniodental shape and size variation observed for a single extant species of papionin. To test the first hypothesis, we assessed a subset of relatively complete and well-preserved Parapapio crania (n=16), intentionally without reference to previous taxonomic identifications. Specimens were sorted by similarity in cranial features and results were then compared with published taxonomic classifications. Our results demonstrate that morphological traits do not cluster consistently according to the current species categories within Parapapio, failing to reject our first hypothesis. To test our second hypothesis, we examined variation in cranial and dental metrics within Parapapio (n=64) relative to three extant papionin samples (n=310). Our results fail to reject the hypothesis that all Parapapio specimens could belong to a single species and suggest that the three-species paradigm does not reflect the anatomical variation of this genus. We recommend subsuming all Parapapio specimens within Parapapio broomi, the species name with taxonomic priority. The results of this hypothesis-testing approach to taxonomy carry substantial implications for the taxonomy of Parapapio, as well as for biochronological and paleoecological studies more generally, including the taxonomy and paleobiology of hominids recovered from these same deposits. 

The diversity of vertebrate skeletons is often attributed to adaptations to distinct ecological factors such as diet, locomotion, and sensory environment. Although the adaptive evolution of skull, appendicular skeleton, and vertebral column is well studied in vertebrates, comprehensive investigations of all skeletal components simultaneously are rarely performed. Consequently, we know little of how modes of evolution differ among skeletal components. Here, we tested if ecological and phylogenetic effects led to distinct modes of evolution among the cranial, appendicular and vertebral regions in extant carnivoran skeletons. Using multivariate evolutionary models, we found mosaic evolution in which only the mandible, hindlimb and posterior (i.e. last thoracic and lumbar) vertebrae showed evidence of adaptation towards ecological regimes whereas the remaining skeletal components reflect clade-specific evolutionary shifts. We hypothesize that the decoupled evolution of individual skeletal components may have led to the origination of distinct adaptive zones and morphologies among extant carnivoran families that reflect phylogenetic hierarchies. Overall, our work highlights the importance of examining multiple skeletal components simultaneously in ecomorphological analyses. Ongoing work integrating the fossil and palaeoenvironmental record will further clarify deep-time drivers that govern the carnivoran diversity we see today and reveal the complexity of evolutionary processes in multicomponent systems. 

Abstract ObjectivesThe goals of this study were to describe and interpret two new fossil assemblages of cercopithecin monkeys (n = 328), one from the Faro Daba beds (ca. 100,000 years) and the other one from the Chai Baro beds (>158,000 years old), in the Afar Rift of Ethiopia. Materials and MethodsWe describe the two assemblages and compare them to extant cercopithecin species and the smaller fossil assemblage from Asbole, Ethiopia (ca. 600 ka). We use a population‐based approach to the taxonomy given the unusually large number of specimens. Craniodental and postcranial anatomy are presented. Evidence of locomotor habitus is described and evaluated in a framework of hybridization and postcranial plasticity. ResultsWe attribute all cercopithecin specimens from both beds to cf.Chlorocebusand conclude that the Faro Daba and Chai Baro assemblages likely sample single species at each time horizon. Subtle differences between the two assemblages, mostly in postcranial morphology, are insufficient to justify separation at the species level. DiscussionThe large sample sizes and unique preservational aspects of these two assemblages open a new window into the recent evolution of guenons. Our data indicate that these fossil populations may be ancestral to the cercopithecins currently living in the Afar region of Ethiopia.