Abstract
Mammal tooth morphology and function correlate strongly with dietary ecology, and convergence is a major feature of mammalian tooth evolution. Yet, function and ecology are insufficient to explain morphological diversification and convergence within mammalian molar evolution; suggesting that development and phylogeny also limit possible structural solutions to selective pressures. Here, I use in silico models and empirical studies of extant and fossil rodent teeth to identify morphogenetic rules that influence molar morphology. Because rodents are the most diverse group of mammals with corresponding dental disparity they represent an excellent system for investigating how genetic interactions limit morphology. I find that lower first molars are limited to a minimum of four cusps and a maximum of nine cusps. Multiple developmental pathways produce the same numbers of cusps, despite highly variable cusp morphologies, indicating the existence of limits on how morphological evolution can fill a morphospace defined by cusp numbers. These constraints are both developmental and phylogenetic in nature and the identification of their influence on rodent molar shape provides a framework for investigation of how tooth batteries evolved an array of functions despite fundamental structural limits. The data presented here increase predictability of cusp number and evolutionary outcomes of rodent cheek dentition.
Highlights
Constraint is most readily recognized in three major forms; functional, developmental, and phylogenetic
In silico modeling reveals that increasing initial activator (ACT) concentration over wild-type (WT) conditions can induce additional enamel knots (EKs) on a modeled tooth, but there appears to be a limit of six EKs that can be added by modeling ACT alone (Fig. 1)
Cusp counts of cheekteeth of 48 extant and extinct rodent species ranged between 12–28 cusps total in the toothrow (SI Table 1)
Summary
Constraint is most readily recognized in three major forms; functional, developmental, and phylogenetic. Rodents are the most taxonomically diverse group of living mammals, encompassing some 40% of extant mammalian species They are characterized by a wide range of functionally specialized tooth forms, contributing to the www.nature.com/scientificreports/. The “late bell” stage (E20), where ameloblasts are differentiated into the distinct tooth layers commonly recognized (e.g., pulp, dentin, and enamel) and the tooth is ready to erupt Each of these stages are initiated and limited by a host of genetic factors that control organogenesis and odontogenesis (see[1]: and[5] for review). All mammals, share this developmental staging, the basic structures of mammalian teeth are homologous This fact is of critical importance when we investigate the changes to these structures that result in distinct tooth morphologies (and functions)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
