The postorbital is one of the bones in vertebrate skulls which forms a portion of the dermal skull roof and, sometimes, a ring about the orbit. Generally, it is located behind the postfrontal and posteriorly to the orbital fenestra. In some vertebrates, the postorbital is fused with the postfrontal to create a postorbitofrontal. Classes and Clades Vertebrata is a subphylum of chordates, specifically, those with backbones or spinal columns. ... Fenestrae (singular: fenestra) are small pores in epithelial cells to allow for rapid exchange of molecules between blood vessels and surrounding tissue. ...
Roemer, A. S. 1956. Osteology of the Reptiles. University of Chicago Press. 772 pp.
Elzanowski (2002) commented on the homologies of the postorbital process and noted that the laterosphenoid, frontal, and parietal all contribute to this process in Archaeopteryx, as in neornithines.
A rostral process, forked slightly at its apex, has been consistently interpreted as a postorbital process of the squamosal (e.g., Paul 2002), and has been used to triumphantly deduce the presence of a complete dorsal temporal bar in the urvogel.
In a similar vein, the vigorous assertion that the presence of the postorbital in Archaeopteryx is confirmed by the amorphous structure in HMN 1880 (the Berlin specimen), an argument dating from Heilmann (1926), must itself be questioned vigorously.
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