Molar Shape, Function, and Tooth Wear in the Evolution of Cercopithecoid Bilophodonty

Description
Crown Cercopithecoidea (Old World monkeys) share bilophodont molars characterized by four cusps arranged into two transversely-aligned pairs connected by crests or “loph(id)s”. This derived dental configuration provides a flexible template that has been modified in different lineages of Old World

Crown Cercopithecoidea (Old World monkeys) share bilophodont molars characterized by four cusps arranged into two transversely-aligned pairs connected by crests or “loph(id)s”. This derived dental configuration provides a flexible template that has been modified in different lineages of Old World monkeys to meet the mechanical demands of food-processing in species with diverse and varied diets. This molar Bauplan evolved in the early stages of Old World monkey evolution, and one consequence of these morphological changes in occlusal morphology relative to apes and more basal catarrhines is a set of distinct patterns of tooth wear. Adaptive explanations for the origins of bilophodonty have emphasized dietary reconstructions but have not explored the implications of molar crown reorganization on the interaction between tooth wear and tooth function. This study combines description of new fossil material of early Miocene stem cercopithecoids and 3D dental topographic analyses of cross-sectional M2 wear series of extant catarrhines (n=511, 24 species) and Miocene fossil catarhines (n=81, 7 genera) to explore how functional aspects of molar topography are altered by tooth wear, to test whether the acquisition of bilophodont molars resulted in distinct occlusal topographies and patterns of topographic change with wear among Old World monkeys, and to determine whether differences in patterns of topographic change with wear reflect differences in diet.Descriptions of new fossils of the early Miocene stem cercopithecoid Noropithecus bulukensis confirm its generic distinction from Victoriapithecus macinnesi and highlight the dental metric and morphological variation that complicates identification of isolated teeth. Results of dental topographic analyses show that wear-mediated patterns of change in functional topographic metrics do not reflect broad dietary differences in extant catarrhines. While topographic features of unworn molars exhibit a phylogenetic signal, the pattern of wear-mediated topographic change does not. Molar topography of victoriapithecids is similar to extant cercopithecids with frugivorous and hard-object feeding diets, supporting previous dietary reconstructions. Victoriapithecid molar occlusal surfaces exhibit less complexity, less curvature, and higher relief than proconsulids prior to heavy wear stages. They are not distinct from occlusal topographies of small-bodied non-cercopithecoid catarrhines at any wear stage. Overall, these results suggest that the acquisition of bilophodont molar morphology in early and middle Miocene stem cercopithecoids was not associated with a shift in occlusal topography relative to more basal catarrhines. Rather, it is among proconsulids that shifts toward more complex, higher curvature occlusal surfaces are found.
Date Created
2021
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A Systematic Revision of Proconsul With the Description of a New Genus of Early Miocene Hominoid

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Description

For more than 80 years, Proconsul has held a pivotal position in interpretations of catarrhine evolution in East Africa. From early hypotheses of phyletic relationships with modern apes to more recent debates over their position within Hominoidea, the well-preserved fossils

For more than 80 years, Proconsul has held a pivotal position in interpretations of catarrhine evolution in East Africa. From early hypotheses of phyletic relationships with modern apes to more recent debates over their position within Hominoidea, the well-preserved fossils of this genus have been a foundation for most evolutionary scenarios regarding the early diversification of hominoids. The majority of what we "know" about Proconsul, however, derives from abundant younger fossils found at the Kisingiri localities on Rusinga and Mfangano Islands rather than from the smaller samples found at Koru – the locality of the type species, Proconsul africanus – and other Tinderet deposits. One outcome of this is seen in recent attempts to expand the genus "Ugandapithecus" (considered here a junior subjective synonym of Proconsul), wherein much of the Tinderet sample was referred to that genus based primarily on differentiating it from the Kisingiri specimens rather than from the type species, P. africanus. This and other recent taxonomic revisions to Proconsul prompted us to undertake a systematic review of dentognathic specimens attributed to this taxon. Results of our study underscore and extend the substantive distinction of Tinderet and Ugandan Proconsul (i.e., Proconsul sensu stricto) from the Kisingiri fossils, the latter recognized here as a new genus. Specimens of the new genus are readily distinguished from Proconsul sensu stricto by morphology preserved in the P. africanus holotype, M 14084, but also in I1s, lower incisors, upper and lower canines, and especially mandibular characteristics. A number of these differences are more advanced among Kisingiri specimens in the direction of crown hominoids. Proconsul sensu stricto is characterized by a suite of unique features that strongly unite the included species as a clade. There have been decades of contentious debate over the phylogenetic placement of Proconsul (sensu lato), due in part to there being a mixture of primitive and more advanced morphology within the single genus. By recognizing two distinct clades that, in large part, segregate these character states, we believe that better phylogenetic resolution can be achieved.

Date Created
2015-07-01
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