Dietary constraints of phytosaurian reptiles revealed by dental microwear textural analysis

Biology and Evolution of Crocodylians is a comprehensive review of current knowledge about the world's largest and most famous living reptiles. Gordon Grigg's authoritative and accessible text and David Kirshner's stunning interpretive artwork and colour photographs combine expertly in this contemporary celebration of crocodiles, alligators, caimans and gharials. This book showcases the skills and capabilities that allow crocodylians to live how and where they do. It covers the biology and ecology of the extant species, conservation issues, crocodylian–human interaction and the evolutionary history of the group, and includes a vast amount of new information; 25 per cent of 1100 cited publications have appeared since 2007. Richly illustrated with more than 500 colour photographs and black and white illustrations, this book will be a benchmark reference work for crocodylian biologists, herpetologists and vertebrate biologists for years to come. Winner of the 2015 Whitley Medal.

Background Crocodilians have dominated predatory niches at the water-land interface for over 85 million years. Like their ancestors, living species show substantial variation in their jaw proportions, dental form and body size. These differences are often assumed to reflect anatomical specialization related to feeding and niche occupation, but quantified data are scant. How these factors relate to biomechanical performance during feeding and their relevance to crocodilian evolutionary success are not known. Methodology/Principal Findings We measured adult bite forces and tooth pressures in all 23 extant crocodilian species and analyzed the results in ecological and phylogenetic contexts. We demonstrate that these reptiles generate the highest bite forces and tooth pressures known for any living animals. Bite forces strongly correlate with body size, and size changes are a major mechanism of feeding evolution in this group. Jaw shape demonstrates surprisingly little correlation to bite force and pressures. Bite forces can now be predicted in fossil crocodilians using the regression equations generated in this research. Conclusions/Significance Critical to crocodilian long-term success was the evolution of a high bite-force generating musculo-skeletal architecture. Once achieved, the relative force capacities of this system went essentially unmodified throughout subsequent diversification. Rampant changes in body size and concurrent changes in bite force served as a mechanism to allow access to differing prey types and sizes. Further access to the diversity of near-shore prey was gained primarily through changes in tooth pressure via the evolution of dental form and distributions of the teeth within the jaws. Rostral proportions changed substantially throughout crocodilian evolution, but not in correspondence with bite forces. The biomechanical and ecological ramifications of such changes need further examination.