In nocturnal animals, the tapetum lucidum acts like a mirror, reflecting light back through the retina and stimulating photoreceptors a second time, a process that basically doubles visual sensitivity. This heightened ability to see in the dark is useful for hunting—or to avoid being hunted.

“We know basically nothing about the evolution, genetics, and developmental biology of the tapetum,”

“The tapetum has appeared and disappeared countless times throughout the evolution and diversification of animals,”