Meeting Abstract

P2.68  Wednesday, Jan. 5  The evolution of bird skull shapes and modeling the mechanisms of beak function OLSEN, A.M.*; WESTNEAT, M.W.; University of Chicago, IL; Field Museum of Natural History, Chicago, IL aolsen@uchicago.edu

A diversity of beak shapes have emerged from the evolutionary history of birds, yet the adaptive and functional consequences of these shapes are still only partly understood. While questions of bird beak function often focus predominately on foraging, a growing body of literature suggests functional consequences of bird beaks for preening, sexual selection and thermoregulation. Laying the groundwork for more complete explanations of the structure-function relationship for bird beaks we ask the question, how are bird beaks and their underlying jaw mechanisms distributed in morphospace? We adapted the direct linear transformation (DLT) technique for rapid and low-cost collection of 3D morphometrics from museum specimens and assessed its precision. Using this technique, we obtained three-dimensional morphometrics on both osteological and fresh specimens, sampling a broad range of avian taxa. We then developed a three-dimensional, kinematic linkage model of the upper and lower beak and the mechanisms of quadrate, pterygoid and jugal coupling between upper and lower jaws. Our model predicts kinematic parameters, such as maximum gape and an upper-to-lower beak displacement ratio for coupled kinesis, as well as kinetic parameters, such as force transmission from the quadrate to the jaws. Plotting both morphological parameters and functional parameters predicted from morphology, we found the distribution of our sampled taxa in morphospace. Placing the results of our morphological survey into a phylogenetic context will refine our understanding of the factors that have shaped bird beaks throughout evolution.