Meeting Abstract

8.5  Saturday, Jan. 4 08:32  Variation on an Old Articulation: Diverse material properties of a key joint underlying avian cranial kinesis OLSEN, AM*; WESTNEAT, MW; Univ of Chicago; Field Museum of Natural History aolsen@uchicago.edu

Bird beaks are known for their fantastic variation in shape and diversity of functions, including feeding, preening and vocalizing. But birds are additionally diverse in how they move their beaks. It has been demonstrated that several bird species, from sparrows to mallards, can move not only their lower beak but their upper beak as well. In most birds, movement of the upper beak depends on a flexible joint between the frontal and nasal bones, called the nasofrontal joint. While there have been many studies of beak shape diversity, there has not been a single comparative study of the material properties of the nasofrontal joint across birds. We have developed a new method to cheaply and accurately measure joint torsional resistance in biological specimens. Applying this method, we measured the torsional resistance of the nasofrontal joint to upper beak protraction (raising of the upper beak) in fresh-frozen specimens representing several bird orders. We present the first evidence that this key joint has diverse material properties across birds. This dataset provides an opportunity to test whether the material properties of the nasofrontal joint are related to beak function and a first chance to test hypotheses on the potential function or functions of cranial kinesis in birds.