The postorbital of a duck embryo fusing with the frontal during development.

A skull diagram of Dromaeosaurus, a dromaeosaurid dinosaur. The postorbital is colored dark blue.

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.