44-2 Friday, Jan. 5 08:15 - 08:30 The elegance of ever-growing incisors: biomechanics and ecomorphology of unique rodent dentition and musculature as the drivers of diversification KRENTZEL, D*; ANGIELCZYK, K; Univ. of Chicago; Field Museum firstname.lastname@example.org
Rodents comprise the majority of mammal species and present the widest array of diets, but their incisors appear simple and conservative. We argue that the ever-growing incisors of rodents are an elegant tool for manipulating their environment, driving their diversification. These teeth are unique among mammals due to their specialized self-sharpening adaptations and functional decoupling of gnawing from chewing. Here we assess the relationship between incisor shape and diet/function across a representative sample of 271 rodent genera spanning each masseteric configuration in order describe how incisor shape is adapted for specialized and generalized masticatory functions. Our results demonstrate that incisor size and shape are unrelated to cheekteeth size and shape across rodent phylogeny, corroborating the hypothesized independent functional utilization of these modules within the feeding system in rodents. We find that rodent lineages lacking a myomorphic masseteric configuration (in which there are two specialized anterior masseter units instead of one) are often specialized in diet and exhibit incisors with unique morphologies for vegetative cropping, digging, and hard nut/seed feeding. Myomorphic rodents, despite their wide diversity of diets and high diversification rates, demonstrate more conservative incisal morphologies. We argue that the simplicity of ever-growing incisors has allowed rodents to achieve the most extreme ecomorphological versatility in mammals, and that myomorphic species in particular exhibit even further dietary lability without the same diversity of incisor shapes thanks to the synergistic interaction between their derived anterior masseteric units during gnawing.