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. Birds have a separate postorbital as an
embryo, but the bone fuses with the
frontal before it hatches.
References
Roemer, A. S. 1956. Osteology of the Reptiles. University of Chicago Press. 772 pp.