Postfrontal bone

The postfrontal is a paired cranial bone found in many tetrapods. It occupies an area of the skull roof between and behind the orbits (eye sockets), lateral to the frontal and parietal bones, and anterior to the postorbital bone.

The postfrontal forms part of the rear and upper border of the eye socket when present. It is particularly large in many extinct amphibians and their sarcopterygian (lobe-finned fish) ancestors, stretching forwards to contact the prefrontal, thus separating the frontal from the rim of the orbit. In living amphibians (lissamphibians), the postfrontal is absent, having failed to ossify during development.^[1] The postfrontal is present but reduced in some reptiles, including modern squamates (lizards and snakes). It is lost or fused to surrounding bones in mammals, crocodylomorphs^[2] (including crocodilians) and dinosaurs (including birds),^[3] though it is present in other extinct archosaurs.

References

1. Schoch, Rainer R. (2014). "Amphibian skull evolution: The developmental and functional context of simplification, bone loss and heterotopy: AMPHIBIAN SKULL EVOLUTION". Journal of Experimental Zoology Part B: Molecular and Developmental Evolution (9999B): 1–12. doi:10.1002/.22599.
2. Benton, Michael J.; Clark, James M. (1988). "8. Archosaur phylogeny and the relationships of the Crocodylia". In Benton, Michael J. (ed.). The Phylogeny and Classification of the Tetrapods, Volume 1: Amphibians, Reptiles, Birds. Oxford: Clarendon Press. pp. 295–338.
3. Sereno, Paul C.; Novas, Fernando E. (1994-01-14). "The skull and neck of the basal theropod Herrerasaurus ischigualastensis". Journal of Vertebrate Paleontology. 13 (4): 451–476. doi:10.1080/02724634.1994.10011525. ISSN 0272-4634.