Editing Reptile (section)

===Digestion===
[[File:PikiWiki Israel 37648 Nature and Colors.jpg|thumb|right|A colubrid snake, ''[[Dolichophis jugularis]]'', eating a [[sheltopusik|legless lizard]], ''Pseudopus apodus''. Most reptiles are carnivorous, and many primarily eat other reptiles and small mammals.]]
<!--[[File:Watersnake.JPG|thumb|Watersnake ''[[Malpolon monspessulanus]]'' eating a lizard.]]-->
[[File:PSM V53 D226 Silicious pebbles from the stomach of a plesiosaur.jpg|thumb|right|[[Gastrolith]]s from a [[plesiosaur]]]]

Most reptiles are insectivorous or carnivorous and have simple and comparatively short digestive tracts due to meat being fairly simple to break down and digest. [[Digestion]] is slower than in [[mammals]], reflecting their lower resting [[metabolism]] and their inability to divide and [[masticate]] their food.<ref>{{cite book |author=Karasov, W.H. |year=1986 |chapter=Nutrient requirement and the design and function of guts in fish, reptiles and mammals |editor=Dejours, P. |editor2=Bolis, L. |editor3=Taylor, C.R. |editor4=Weibel, E.R. |title=Comparative Physiology: Life in water and on land |publisher=Liviana Press/Springer Verlag |isbn=978-0-387-96515-4 |pages=181–191 |chapter-url=https://books.google.com/books?id=zuT5z5cPWhcC&dq=reptiles+carnivory+gastric&pg=PA181 |access-date=November 1, 2012}}</ref> Their [[poikilotherm]] metabolism has very low energy requirements, allowing large reptiles like crocodiles and large constrictors to live from a single large meal for months, digesting it slowly.<ref name=Garnett/>

While modern reptiles are predominantly carnivorous, during the early history of reptiles several groups produced some herbivorous [[megafauna]]: in the [[Paleozoic]], the [[pareiasaur]]s; and in the [[Mesozoic]] several lines of [[dinosaur]]s.<ref name=Sahney-Benton-Ferry-2010/> Today, [[turtle]]s are the only predominantly herbivorous reptile group, but several lines of [[Agamidae|agamas]] and [[Iguanidae|iguanas]] have evolved to live wholly or partly on plants.<ref name=herbivory>{{cite book |last=King |first=Gillian |year=1996 |title=Reptiles and Herbivory |edition=1 |publisher=Chapman & Hall |location=London, UK |isbn=978-0-412-46110-1}}</ref>

Herbivorous reptiles face the same problems of mastication as herbivorous mammals but, lacking the complex teeth of mammals, many species swallow rocks and pebbles (so called [[gastrolith]]s) to aid in digestion: The rocks are washed around in the stomach, helping to grind up plant matter.<ref name=herbivory/> Fossil gastroliths have been found associated with both [[ornithopod]]s and [[sauropods]], though whether they actually functioned as a gastric mill in the latter is disputed.<ref>{{cite journal|last=Cerda|first=Ignacio A. |date=1 June 2008|title=Gastroliths in an ornithopod dinosaur|journal=Acta Palaeontologica Polonica |volume=53|issue=2|pages=351–355|doi=10.4202/app.2008.0213|doi-access=free}}</ref><ref>{{cite journal |author1=Wings, O. |author2=Sander, P.M. |title=No gastric mill in sauropod dinosaurs: new evidence from analysis of gastrolith mass and function in ostriches |journal=Proceedings of the Royal Society B: Biological Sciences |date=7 March 2007 |volume=274 |issue=1610 |pages=635–640 |doi=10.1098/rspb.2006.3763 |pmc=2197205  |pmid=17254987}}{{open access}}</ref> [[Salt water crocodile]]s also use gastroliths as [[Sailing ballast|ballast]], stabilizing them in the water or helping them to dive.<ref>{{cite journal|last=Henderson|first=Donald M.|title=Effects of stomach stones on the buoyancy and equilibrium of a floating crocodilian: a computational analysis|journal=Canadian Journal of Zoology|date=1 August 2003|volume=81|issue=8|pages=1346–1357|doi=10.1139/z03-122|bibcode=2003CaJZ...81.1346H }}</ref> A dual function as both stabilizing ballast and digestion aid has been suggested for gastroliths found in [[plesiosaur]]s.<ref>{{cite journal|last=McHenry|first=C.R.|title=Bottom-Feeding Plesiosaurs|journal=Science|date=7 October 2005|volume=310|issue=5745|pages=75|doi=10.1126/science.1117241|pmid=16210529|s2cid=28832109}}{{open access}}</ref>