Though all four were outside the head of our fish ancestors, they migrated back inside as evidenced by the discovery of Kenichthys campbelli, a 395 million-year-old fossilized fish which shows this migration in progress.
It is also known by the proper name Minchir, and appears as Minchir es-schudscha
Jeff "Swampy" Marsh, a storyboard writer, says that Heffer's right eye and left nostril are "notched at the bottom" due to Murray's design style.
In bony fish, amphibians, and reptiles, both maxilla and premaxilla are relatively plate-like bones, forming only the sides of the upper jaw, and part of the face, with the premaxilla also forming the lower boundary of the nostrils.
The fossil lungfish Diabolepis shows an intermediate stage between posterior and interior nostril and supports the independent origin of internal nostrils in the lungfish.
These postulated diverticula would have taken the form of inflatable soft-tissue sacs housed in the deep excavations flanking the crest and elongate holes for the nostrils.
Ear-opening not or but slightly larger than the nostril; third to sixth upper labials below the eye.