Meeting Abstract

82-7   15:00 - 15:15  Diphyodont dilemma - are teeth too costly or jaws too weak? Cohen, KE*; Summers, AP; University of Washington, Seattle WA; University of Washington, Seattle WA kecohen@uw.edu

here are two mutually exclusive hypotheses for the evolution of diphyodont dentitions. The first considers that enamel is expensive and that maintaining a polyphyodont dentition is metabolically challenging. Alternatively, a close-fitting occlusal surface cannot be maintained by continuously replacing teeth. However, there is no evidence that dental batteries are expensive - sharks replace their teeth at high rates and have done so for millions of years, and some teleosts replace 3% of their dentition a day. And, several lineages of fishes have a dental battery with excellent, high performance occlusion between upper and lower teeth (piranhas, parrot fishes, and eagle rays) that they use to chew and manipulate complex prey. We propose an alternative hypothesis: the evolution of diphyodont dentitions is driven by the constant remodeling needed for continuous tooth replacement, which undermines the stiffness of the jaw. In other words, polyphyodont jaws are unable to resist high chewing stress, instead relying on a constantly sharp dentition to efficiently break down prey. To understand the trade-offs between jaw morphology and replacement strategy we propose to follow the evolution of diphyodonty across vertebrates to see how many times diphyodonty appears and how many strategies precede polyphyodonty. We expect the distribution of stress on jaws will be radically altered as bone dissolves during tooth replacement. We predict that diphyodont vertebrates will cluster in morphospace away from polyphyodonts.