This differs from tarsiers, which lack a tapetum lucidum but possess a fovea. Other sources say they have a tapetum lucidum composed of collagen fibrils. The choroid is very thick and contains a fibrous "tapetum lucidum". The tapetum lucidum contributes to the superior night vision of some animals. Eyeshine is a visible effect of the tapetum lucidum. Apart from its eyeshine, the tapetum lucidum itself has a color. The tapetum lucidum, present in the eyes of many vertebrates, is also iridescent. Crocodilians possess a "tapetum lucidum" which enhances vision in low light. Both species have a "tapetum lucidum", so their pupils may display eyeshine. Haplorhine primates, including humans, are diurnal and lack a "tapetum lucidum". Deer also have a tapetum lucidum, which gives them sufficiently good night vision. Humans, and monkeys, lack a "tapetum lucidum". Coelacanth eyes are very sensitive, and have a "tapetum lucidum". However, the "tapetum lucidum" cells are leucophores, not iridophores. The color corresponds approximately to the type of tapetum lucidum, with some variation between species.