Meeting Abstract
Few species evolved skulls as derived as ducks and other anseriform birds, which employ rapid, dexterous movements of the palate and jaws to feed. Despite their exceptional behavior and morphology, little is known about the structure and biomechanics of their jaw muscles, cranial joints, and linkages that facilitate cranial kinesis. The lower temporal bar (quadratojugal and jugal) links the quadrate and the upper beak and is flexible, but the structural properties underlying this flexibility remain unclear. We dissected the lower temporal bars from a sample of Mallard ducks. One side was fixed, imaged in microCT, and followed by histological sectioning at three focal areas. The contralateral side was tested in three-point bending following standard protocols to estimate whole element stiffness. We found the lower temporal bar was less mineralized than the quadrate overall, and became less dense rostrally. Second moments of area show that the lower temporal bar is about six times more resistant to bending about the mediolateral axis. Histologically, the lower temporal bar is homogeneously constructed and resembles an avian mineralized tendon instead of cranial intramembranous bone. The Young’s moduli of the element are intermediate between mammalian fetal bone and haversian bone. We conclude that the flexibility of the lower temporal bar of ducks results from several changes to the shape and composition of the bone. This suggests birds may employ a diversity of modifications to skeletal tissues to facilitate flexibility in the bones of the feeding apparatus.
