In class, your professor shows you the skulls of three mammals. In one, the eye would be fully enclosed by bone. In the second,
there is a bony circle around where the eye goes, but it is open in the back. In the third, the place where the eye would be is not encircled by bone at all. This suggests to you that a. the first one is an anthropoid primate; the fully enclosed orbit is probably beneficial in an organism that relies heavily on vision. b. all three species are probably nocturnal; otherwise, it would be impossible to find evidence of eyes given only the skull. c. the third one is an anthropoid primate, because an organism with a highly developed sense of vision needs more room to move the eyes around. d. the second one, with the bony bar around the eye, is probably not a primate.
It is more probable that the third one has a more developed sense of the vision with a large eye, and its movements. Also with a opened back to receive its nutrition and optic nerve.
Sources:
Zihlman, Adrienne. (2006). «The Ape in the Tree». International Journal of Primatology (en inglés) 27 (4): 1227-1228
