%0 Journal Article
%T Making Space for Permanent Molars in Growing Baboon (Papio anubis) and Great Ape (Pan paniscus and P. troglodytes) Mandibles: Possible Ontogenetic Strategies and Solutions
%A Julia C. Boughner
%J Anatomy Research International
%D 2011
%I Hindawi Publishing Corporation
%R 10.1155/2011/484607
%X While mandible proportions do not appear to constrain permanent molar initiation times, how adequate space is created in the corpus for these teeth in a timely way is not well understood. This question is important for explaining how primate tooth and jaw development and evolution are coordinated. Landmark and linear measurement data were used to characterize mandible shape, growth trajectory, and growth rate between two genera, Papio and Pan, with contrasting permanent molar initiation schedules and mandible proportions. 3D geometric morphometric and 2D bivariate analyses showed genus-level differences in mandible morphology from birth that were amplified by different postnatal growth trajectories. Different corpus proportions and regional variation in corpus growth rates helped create space in a timely way for the molars. Regional corpus growth rates may evolve alongside permanent molar morphology and developmental timing to modify space available in the corpus for these teeth. 1. Introduction Primate mandible morphologies and times of permanent molar initiation, used here to define the start of odontogenesis, vary widely across taxa. How sufficient space is created for the developing permanent molars in a growing mandible of a particular morphology at appropriate times is not well understood. Once emerged, the deciduous dentition maintains a large proportion of the space in the mandible corpus required for the permanent antemolar teeth. But for the permanent molars, space must be created anew via the growth of the jawbone. The timing of permanent molar initiation as well as molar mineralization rates and periods varies, often markedly, among primates [1¨C8]. Times of permanent molar initiation are not likely to be constrained by a lack of space for these teeth in the growing jaw [9]. Other work also suggests ontogenetic if not evolutionary autonomy between the teeth and the mandible [10¨C17], where teeth experience stronger selection pressures than do the jaws and face [17¨C19]. At least in African apes, the growth of tooth-bearing regions of the mandible is less plastic than that of edentulous regions of the jaw, notably areas of muscle attachment [20]. There is also evidence based on African ape data of developmental decoupling among various regions of the mandible corpus, ramus, condyle, and alveolar versus cortical bone that appears to be a response to the different functions of these skeletal tissues [20]. Specifically, the presence and development of the dentition may influence mandible corpus form and growth [21¨C24]. For example, the timing of
%U http://www.hindawi.com/journals/ari/2011/484607/