title: Morphometric variation of extant platyrrhine molars: taxonomic implications for fossil platyrrhines.
abstract: The phylogenetic position of many fossil platyrrhines with respect to extant ones is not yet clear. Two main hypotheses have been proposed: the layered or successive radiations hypothesis suggests that Patagonian fossils are Middle Miocene stem platyrrhines lacking modern descendants, whereas the long lineage hypothesis argues for an evolutionary continuity of all fossil platyrrhines with the extant ones. Our geometric morphometric analysis of a 15 landmark-based configuration of platyrrhines' first and second lower molars suggest that morphological stasis may explain the reduced molar shape variation observed. Platyrrhine lower molar shape might be a primitive retention of the ancestral state affected by strong ecological constraints throughout the radiation of the main platyrrhine families. The Patagonian fossil specimens showed two distinct morphological patterns of lower molars, Callicebus-like and Saguinus-like, which might be the precursors of the extant forms, whereas the Middle Miocene specimens, though showing morphological resemblances with the Patagonian fossils, also displayed new, derived molar patterns, Alouatta-like and Pitheciinae-like, thereby suggesting that despite the overall morphological stasis of molars, phenotypic diversification of molar shape was already settled during the Middle Miocene.
authors.affiliation: Department of Evolutionary Biology, Ecology and Environmental Sciences, Zoology and Physical Anthropology Section, Universitat de Barcelona , Barcelona , Spain.
authors.forename: Mónica
authors.initials: M
authors.lastname: Nova Delgado
authors.affiliation: Department of Evolutionary Biology, Ecology and Environmental Sciences, Zoology and Physical Anthropology Section, Universitat de Barcelona, Barcelona, Spain; Center for the Advanced Study of Human Paleobiology, Department of Anthropology, George Washington University, Washington DC, United States of America.
authors.forename: Jordi
authors.initials: J
authors.lastname: Galbany
authors.affiliation: Department of Evolutionary Biology, Ecology and Environmental Sciences, Zoology and Physical Anthropology Section, Universitat de Barcelona , Barcelona , Spain.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Pérez-Pérez
keywords: Geometric morphometric; Molar shape; Phylogeny; Platyrrhines