I am surprised that the pineal eye was not mentioned in this article.
Living fossils like the remora have a pineal eye but so do tuataras, a land dwelling lizard. Dog brains occasionally feature pineal eyes. It also gets tons of mention in reference to the egyptian god Horus, who had a third eye. in humans, the pineal gland (in the third ventricle of the brain, produces serotonin and melatonin, derivatives of tryptophan, possibly explaining the feelings of well being and sleepiness on thanksgiving) is the only body part sensitive to light through the retinohypothalmic tract. Organisms with pineal eyes have taken the middle man out of the equation and just expose extensions of the gland directly to sunlight (a better argument for trephening the depressed insomniac has never been made). Occasional mutations in humans reveal similar projections in humans.
Also, this is just for the curious in the audience, would you like to see what inspired the legend of the cyclops? Just google holoprosencephaly.