Editing Night monkey (section)

==Physical characteristics==
Night monkeys have large brown eyes; the size improves their nocturnal vision increasing their ability to be active at night. They are sometimes said to lack a [[tapetum lucidum]], the reflective layer behind the retina possessed by many nocturnal animals.<ref name = "Schwab2002">{{cite journal
 | last1 = Schwab | first1 = I. R. | last2 = Yuen | first2 = C. K.
 | last3 = Buyukmihci | first3 = N. C. | last4 = Blankenship | first4 = T. N.
 | last5 = Fitzgerald | first5 = P. G. | title = Evolution of the tapetum
 | journal = Transactions of the American Ophthalmological Society
 | volume = 100 | pages = 187–200 | date = 2002 | pmc = 1358962 | pmid=12545693}}</ref> Other sources say they have a tapetum lucidum composed of [[collagen]] fibrils.<ref name="Ollivier2004">{{cite journal|last1=Ollivier|first1=F. J.|last2=Samuelson|first2=D. A.|last3=Brooks|first3=D. E.|last4=Lewis|first4=P. A.|last5=Kallberg|first5=M. E.|last6=Komaromy|first6=A. M.|title=Comparative morphology of the tapetum lucidum (among selected species)|journal=Veterinary Ophthalmology|volume=7|issue=1|date=2004-01-26|pages=11–22|doi=10.1111/j.1463-5224.2004.00318.x|pmid=14738502}}</ref> At any rate, night monkeys lack the tapetum lucidum composed of riboflavin crystals possessed by lemurs and other [[strepsirrhines]],<ref name="Ollivier2004" /> which is an indication that their nocturnality is a secondary adaption evolved from ancestrally diurnal primates.

Their ears are rather difficult to see; this is why their genus name, ''Aotus'' (meaning "earless") was chosen. There is little data on the weights of wild night monkeys. From the figures that have been collected, it appears that males and females are similar in weight; the heaviest species is [[Azara's night monkey]] at around {{Convert|1254|g|lb}}, and the lightest is [[Brumback's night monkey]], which weighs between {{Convert|455|and|875|g|lb}}. The male is slightly taller than the female, measuring {{Convert|346|and|341|mm|in}}, respectively.<ref name=Lang/>