Editing Tapetum lucidum (section)

==Classification==
A [[Biological classification|classification]] of anatomical variants of tapeta lucida<ref name="Ollivier+2004"/><!-- classification is not Ollivier's; dates from 1967 or before --> defines four types:
# ''Retinal tapetum'', as seen in [[teleost]]s (with a variety of reflecting materials from [[Lipid|lipids]] to [[phenols]]), [[crocodile]]s (with [[guanine]]), [[marsupial]]s (with lipid spheres), and [[fruit bat]]s (with [[Phospholipid|phospholipids]]).<ref name="Ollivier+2004"/>{{rp|16}} The tapetum lucidum is within the [[retinal pigment epithelium]]; in the other three types the tapetum is within the [[choroid]] behind the retina. Two anatomical classes can be distinguished: occlusible and non-occlusible.
#* The [[brownsnout spookfish]] has an extraordinary focusing mirror derived from a retinal tapetum.<ref name="pmid19110427">{{cite journal 
|vauthors=Wagner HJ, Douglas RH, Frank TM, Roberts NW, Partridge JC
| title = A novel vertebrate eye using both refractive and reflective optics | journal = Curr. Biol.
| volume = 19
| issue = 2
| pages = 108–114
|date=January 2009
| pmid = 19110427
| doi = 10.1016/j.cub.2008.11.061
| doi-access = free
| bibcode = 2009CBio...19..108W }}</ref>
# ''[[Choroid]]al guainine tapetum'', as seen in [[chondrichthyes|cartilaginous fish]].<ref name="DentonandNichol1964">{{cite journal |author1=Denton, EJ |author-link=Eric James Denton |author2=Nichol, JAC |title=The chorioidal tapeta of some cartilaginous fishes (Chondrichthyes) |journal=J. Mar. Biol. Assoc. U. K. |volume=44 |pages=219–258 |year=1964 |issue=1 |doi=10.1017/S0025315400024760 |bibcode=1964JMBUK..44..219D |s2cid=84527918 |url=http://sabella.mba.ac.uk/2257/01/The_chorioidal_tapeta_of_some_cartilaginous_fishes_(Chondrichthyes).pdf |access-date=2011-09-12 |archive-url=https://web.archive.org/web/20120322163635/http://sabella.mba.ac.uk/2257/01/The_chorioidal_tapeta_of_some_cartilaginous_fishes_(Chondrichthyes).pdf |archive-date=2012-03-22 }}</ref> The tapetum is a palisade of cells containing stacks of flat hexagonal crystals of [[guanine]].<ref name="Locket1974">{{cite journal |author=Locket NA |title=The choroidal tapetum lucidum of ''Latimeria chalumnae'' |journal=Proceedings of the Royal Society B |volume=186 |issue=84 |pages=281–290 |date=July 1974 |pmid=4153107 |doi= 10.1098/rspb.1974.0049|bibcode=1974RSPSB.186..281L |s2cid=38419473 }}</ref>
# ''Choroidal tapetum cellulosum'', as seen in [[carnivore]]s, [[rodent]]s, and [[cetacea]]. The tapetum consists of layers of cells containing organized, highly refractive crystals. These crystals are diverse in shape and makeup: dogs and ferrets use [[zinc]], cats use [[riboflavin]] and zinc, and lemurs use only riboflavin.<ref name="Ollivier+2004"/>{{rp|17}}
# ''Choroidal tapetum fibrosum'', as seen in [[cow]]s, [[sheep]], [[goat]]s, and [[horse]]s. The tapetum is an array of extracellular fibers, most commonly [[collagen]].<ref name="Ollivier+2004"/>{{rp|17}}

The functional differences between these four structural classes of tapeta lucida are not known.<ref name="Ollivier+2004" />