tuatara parietal eye

[eub]

http://www.animalcorner.co.uk/reptiles/rep_tuatara.html

The tuatara has a third eye on the top of its head called the 'parietal eye'. It has its own lens, cornea, retina with rod-like structures and degenerated nerve connection to the brain, suggesting it evolved from a real eye. The parietal eye is only visible in hatchlings, which have a translucent patch at the top centre of the skull.

Tip from mantisshrimp.