Pterygoid

In tetrapods, the pterygoid is a complex, but relatively stable, paired palatal bone with a number of parts. For the following discussion, it may be best to refer to the images of tetrapod palates at, for example Ornithosuchus, Therapsida, or Palatines. In many tetrapods, it is the largest palatal bone and serves as the main structural support. Most typically, the pterygoids meet extensively on the mid-line of the palate and jointly send a process, the palatal ramus, anteriorly, which may cover the parasphenoid more or less completely. Sometimes this term is used to include the main body of the pterygoid as well. More variably, there are one or two anterolateral processes which go by various names, such as ectopterygoid ramus. In many amniotes, the pterygoid develops a strong transverse process or transverse flange which forms a bar running laterally across the palate. The pterygoid also articulates with (where present) the dorsoventral supports for the palate: the epipterygoid (dorsal) and the basipterygoid process of the braincase. Finally, the pterygoid sends a long, robust quadrate ramus with complex curvature down (posteroventrally) to grasp the quadrate and support the jaw articulation.