Streptostylic kinesis
From EvoWiki
Streptostylic kinesis refers to a system of cranial movement which while characteristic of most birds, is not limited thereto. During streptostyly, when the mouth is opened, the mandible and palate are pushed forward simultaneously and the beak rotates dorsally relative to the braincase, due to a weak flexion zone in the nasals. This streptostylic motion is made possible by several modifications of the cranial elements. Starting caudally and proceeding rostrally, these modifications include a double-headed condyle on the proximal articular surface of the quadrate, an orbital process of the quadrate, no descending process of the squamosal to inhibit forward rotation of the quadrate, a propulsion joint between the quadrate and pterygoid, the lack of a dorsal temporal bar bounding the lateral temporal fenestra, and reduction or loss of a complete postorbital bar caudal to the orbit.
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This page is part of the EvoWiki Encyclopedia of Anatomy and Physiology. |
