Editing Megabat (section)

==Description==
===Appearance===
[[File:Mariana Fruit Bat.jpg|thumb|upright|alt=A bat with black fur viewed in profile from the back. It has a bright yellow mantle of fur on the back of its neck.|Contrasting yellow mantle of the [[Mariana fruit bat]] (''Pteropus mariannus'')]]
Megabats take their name from their larger weight and size; the largest, the [[great flying fox]] (''Pteropus neohibernicus''), weighs up to {{cvt|1.6|kg|lb}};<ref>{{cite book| last=Flannery| first= T.| year=1995| title=Mammals of the South-West Pacific & Moluccan Islands| pages= 271| isbn=0801431506| publisher=Cornell University Press}}</ref> some members of ''Acerodon'' and ''Pteropus'' have wingspans reaching up to {{cvt|1.7|m|ft}}.<ref name="Nowak 1994"/>{{rp|p=48}} Despite the fact that body size was a defining characteristic that Dobson used to separate microbats and megabats, not all species of megabat are larger than microbats; the [[spotted-winged fruit bat]] (''Balionycteris maculata''), a megabat, weighs only {{cvt|14.2|g|oz}}.<ref name="Hutcheon 2004">{{cite journal|doi=10.1023/B:JOMM.0000047340.25620.89|title=Are Megabats Big?|journal=[[Journal of Mammalian Evolution]]|volume=11|issue=3/4|pages=257–277|year=2004|last1=Hutcheon|first1=J. M.|last2=Garland|first2=T. Jr.|s2cid=11528722}}</ref> The flying foxes of ''Pteropus'' and ''[[Acerodon]]'' are often taken as exemplars of the whole family in terms of body size. In reality, these genera are outliers, creating a misconception of the true size of most megabat species.<ref name="Hutcheon 2006"/> A 2004 review stated that 28% of megabat species weigh less than {{cvt|50|g|oz}}.<ref name="Hutcheon 2004"/>

Megabats can be distinguished from microbats in appearance by their dog-like faces, by the presence of claws on the second digit (see [[Megabat#Postcrania]]), and by their simple ears.<ref>{{cite book|last1=Geist| first1= V.| first2= D. G.| last2= Kleiman| first3= M. C.| last3= McDade| title= Grzimek's Animal Life Encyclopedia Mammals II| volume= 13| edition= 2nd| publisher=[[Gale (publisher)|Gale]]| year= 2004|page=309}}</ref> The simple appearance of the ear is due in part to the lack of [[tragus (ear)|tragi]] (cartilage flaps projecting in front of the ear canal), which are found in many microbat species. Megabats of the genus ''[[Nyctimene (genus)|Nyctimene]]'' appear less dog-like, with shorter faces and tubular nostrils.<ref name="Nelson"/> A 2011 study of 167 megabat species found that while the majority (63%) have fur that is a uniform color, other patterns are seen in this family. These include [[countershading]] in four percent of species, a neck band or mantle in five percent of species, stripes in ten percent of species, and spots in nineteen percent of species.<ref>{{cite journal|doi=10.1371/journal.pone.0025845|pmid=21991371|pmc=3185059|title=Roosting Ecology and the Evolution of Pelage Markings in Bats|journal=[[PLOS One]]|volume=6|issue=10|page=e25845|year=2011|last1=Santana|first1=S. E.|last2=Dial|first2=T. O.|last3=Eiting|first3=T. P.|last4=Alfaro|first4=M. E.|bibcode=2011PLoSO...625845S|doi-access=free}}</ref>

Unlike microbats, megabats have a greatly reduced [[interfemoral membrane|uropatagium]], which is an expanse of flight membrane that runs between the hind limbs.<ref name="Hall"/> Additionally, the tail is absent or greatly reduced,<ref name="Nelson"/> with the exception of ''Notopteris'' species, which have a long tail.<ref>{{cite journal|doi=10.1071/AM03013|title=Electrophoretic studies of the systematic and biogeographic relationships of the Fijian bat genera Pteropus, Pteralopex, Chaerephon and Notopteris|journal=[[Australian Mammalogy]]|volume=25|page=13|year=2003|last1=Ingleby|first1=S.|last2=Colgan|first2=D.|doi-access=free}}</ref> Most megabat wings insert laterally (attach to the body directly at the sides). In ''[[Dobsonia]]'' species, the wings attach nearer the spine, giving them the common name of "bare-backed" or "naked-backed" fruit bats.<ref name="Hall"/>

===Skeleton===
====Skull and dentition====
[[File:Pteropus melanotus 04 MWNH 237.jpg|thumb|alt=A bat skull with prominent canines on a white background.|Skull of the [[black-eared flying fox]] (''Pteropus melanotus'')]]
Megabats have large [[Orbit (anatomy)|orbits]], which are bordered by well-developed [[postorbital process]]es posteriorly. The postorbital processes sometimes join to form the [[postorbital bar]]. The [[snout]] is simple in appearance and not highly modified, as is seen in other bat families.<ref>{{cite book|last1=Vaughan| first1=T. A.| last2=Ryan| first2=J. M.| last3=Czaplewski| first3=N. J.|title=Mammalogy| date=11 December 2013| publisher=Jones & Bartlett Publishers| isbn=9781284032185| pages=255–256| edition=6|url=https://books.google.com/books?id=GVy2AgAAQBAJ&pg=PA256}}</ref> The length of the snout varies among genera. The [[premaxilla]] is well-developed and usually free,<ref name="Miller, 1907"/> meaning that it is not fused with the [[maxilla]]; instead, it articulates with the maxilla via [[ligament]]s, making it freely movable.<ref>{{cite journal|doi=10.1206/0003-0090(2001)258<0001:PROMBC>2.0.CO;2|issn=0003-0090|year=2001|volume=258|title=Phylogenetic Relationships of Mormoopid Bats (Chiroptera: Mormoopidae) Based on Morphological Data|journal=Bulletin of the American Museum of Natural History|last1=Simmons|first1=Nancy B.|last2=Conway|first2=Tenley M.|hdl=2246/1608|page=17|s2cid=83580917 |url=https://zenodo.org/record/5376511}}</ref><ref>{{cite journal|doi=10.23689/fidgeo-999|year=2011|last1=Lindenau|first1=Christa|title=Middle Pleistocene bats (Mammalia: Chiroptera) from the Yarimburgaz Cave in Turkish Thrace (Turkey)|journal=E&G – Quaternary Science Journal|volume=55|page=127}}</ref> The premaxilla always lack a palatal branch.<ref name="Miller, 1907"/> In species with a longer snout, the skull is usually arched. In genera with shorter faces (''Penthetor'', ''Nyctimene'', ''Dobsonia'', and ''Myonycteris''), the skull has little to no bending.<ref>{{cite journal|url=http://digitallibrary.amnh.org/bitstream/handle/2246/1781/B080a09.pdf;jsessionid=24A463ACFEB3921ED860E6934C4BCE11?sequence=1|title=Results of the Archbold Expeditions No. 48: Pteropodidae (Chiroptera) of the Archbold Collections| last=Tate| first=G. H. H.|year=1942| journal=Bulletin of the American Museum of Natural History| volume=80| pages=332–335}}</ref>

Megabat species have relatively small incisors and large canines. The premolars and molars are adapted to crush and pierce fruit, their primary food source.<ref>Berkovitz, B., & Shellis, P. (2018). The teeth of mammalian vertebrates. Academic Press.</ref> 

The most complete dental formula is: I2/2, C 1/1, P3/3, M2/3 x 2 = 34.<ref>Giannini, N. P., Wible, J. R., & Simmons, N. B. (2006). On the cranial osteology of chiroptera. I. Pteropus (Megachiroptera: Pteropodidae). Bulletin of the American Museum of Natural History, 2006(295), 1-134.</ref> The dental formula of 34 teeth is a homologous trait for megabats.<ref name="Giannini 2007" /> The total number of teeth varies among megabat species, and can range from 24 to 34. For example, some species of megabats have only 2 molars on either side of the lower jaw instead of 3. Others may lack one or more pairs of incisors on the upper or lower jaw.<ref name="Giannini 2007" /> 

All megabats have two to four each of upper and lower [[incisor]]s, with the exception [[Bulmer's fruit bat]] (''Aproteles bulmerae''), which completely lacks incisors,<ref name="Giannini 2007" /> and the [[São Tomé collared fruit bat]] (''Myonycteris brachycephala''), which has two upper and three lower incisors.<ref name="Juste 1993">{{cite journal|last1=Juste| first1= J.| last2= Ibáñez| first2= C.| year=1993| title= An asymmetric dental formula in a mammal, the Sao Tomé Island fruit bat Myonycteris brachycephala (Mammalia: Megachiroptera)| journal= [[Canadian Journal of Zoology]]| volume= 71| issue=1| pages= 221–224| doi= 10.1139/z93-030| bibcode= 1993CaJZ...71..221J| hdl= 10261/48798| hdl-access= free}}</ref> This makes it the only mammal species with an asymmetrical [[dentition#Dental formula|dental formula]].<ref name="Juste 1993" />

All species have two upper and lower [[canine tooth|canine teeth]]. The number of [[premolar]]s is variable, with four or six each of upper and lower premolars.
The first upper and lower [[molar (tooth)|molars]] are always present, meaning that all megabats have at least four molars. The remaining molars may be present, present but reduced, or absent.<ref name="Giannini 2007">{{cite journal|doi=10.1206/0003-0082(2007)3559[1:EHATEO]2.0.CO;2|last1=Giannini| first1= N. P.| last2= Simmons| first2= N. B.| year= 2007| title= Element homology and the evolution of dental formulae in megachiropteran bats (Mammalia: Chiroptera: Pteropodidae)| journal= [[American Museum Novitates]]|issue=3559| pages= 1–27| url=http://digitallibrary.amnh.org/bitstream/handle/2246/5849//v3/dspace/updateIngest/pdfs/N3559.pdf?sequence=1&isAllowed=y|hdl=2246/5849|s2cid=62823404 }}</ref> Megabat molars and premolars are simplified, with a reduction in the [[Cusp (anatomy)|cusps]] and ridges resulting in a more flattened [[crown (tooth)|crown]].<ref name="Wimsatt"/>

Like most mammals, megabats are [[diphyodont]], meaning that the young have a set of [[deciduous teeth]] (milk teeth) that falls out and is replaced by permanent teeth. For most species, there are 20 deciduous teeth. As is typical for mammals,<ref>{{cite journal|last1=Luo| first1= Z. X.| last2= Kielan-Jaworowska| first2=Z.| last3= Cifelli| first3= R. L.| year= 2004| title= Evolution of dental replacement in mammals| journal= Bulletin of Carnegie Museum of Natural History| volume=2004| issue=36| pages=159–176|url=https://pdfs.semanticscholar.org/f49e/b498515c8cf669c24884e66dc55246d0219a.pdf|archive-url=https://web.archive.org/web/20190523184301/https://pdfs.semanticscholar.org/f49e/b498515c8cf669c24884e66dc55246d0219a.pdf|url-status=dead|archive-date=2019-05-23| doi= 10.2992/0145-9058(2004)36[159:EODRIM]2.0.CO;2| s2cid= 5630875}}</ref> the deciduous set does not include molars.<ref name="Wimsatt"/>

====Postcrania====
[[File:Pteropus samoensis-3.jpg|thumb|alt=An articulated bat skeleton on a black background.|Skeleton of the [[Samoa flying fox]] (''Pteropus samoensis'')]]
The [[scapula]]e (shoulder blades) of megabats have been described as the most primitive of any chiropteran family.<ref name="Wimsatt"/> The shoulder is overall of simple construction, but has some specialized features. The primitive insertion of the [[omohyoid muscle]] from the [[clavicle]] (collarbone) to the scapula is [[Anatomical terms of location#Medial and lateral|laterally]] displaced (more towards the side of the body)—a feature [[Convergent evolution|also seen]] in the [[Phyllostomidae]]. The shoulder also has a well-developed system of muscular slips (narrow bands of muscle that augment larger muscles) that anchor the tendon of the occipitopollicalis muscle (muscle in bats that runs from base of neck to the base of the thumb)<ref name="Hall">{{cite book| title=Flying Foxes: Fruit and Blossom Bats of Australia| first1=L. S.| last1= Hall| first2= G.| last2= Richards| year=2000| publisher=[[University of New South Wales|UNSW Press]]|isbn=9780868405612}}</ref> to the skin.<ref name="Nelson"/>

While microbats only have claws on the [[thumb]]s of their forelimbs, most megabats have a clawed second digit as well;<ref name="Wimsatt">{{cite book|editor-last1=Wimsatt| editor-first1= W.| year=1970| title= Biology of Bats| publisher= [[Academic Press]]| isbn=9780323151191|pages=103–136|chapter=Chapter 3: The Skeletal System| last=Vaughan| first=T.}}</ref> only ''Eonycteris'', ''Dobsonia'', ''Notopteris'', and ''Neopteryx'' lack the second claw.<ref name="Nowak">{{cite book|first1=R. M.| last1= Nowak| first2= E.| last2= Pillsbury Walker| year=1999|title=Walker's Mammals of the World| volume=1| publisher=JHU Press| isbn=9780801857898|page=258}}</ref> The first digit is the shortest, while the third digit is the longest. The second digit is incapable of [[flexion]].<ref name="Wimsatt"/> Megabats' thumbs are longer relative to their forelimbs than those of microbats.<ref name="Hall"/>

Megabats' hindlimbs have the same skeletal components as humans. Most megabat species have an additional structure called the [[calcar]], a cartilage spur arising from the [[calcaneus]].<ref name="Bennett"/> Some authors alternately refer to this structure as the uropatagial spur to differentiate it from microbats' calcars, which are structured differently. The structure exists to stabilize the uropatagium, allowing bats to adjust the [[Camber (aerodynamics)|camber]] of the membrane during flight. Megabats lacking the calcar or spur include ''Notopteris'', ''Syconycteris'', and ''[[Harpyionycteris]]''.<ref>{{cite journal|doi=10.1023/A:1020566902992|year=1998|last1=Schutt|first1=W. A.|journal=[[Journal of Mammalian Evolution]]|volume=5|page=2|last2=Simmons|first2=N. B.| title=Morphology and Homology of the Chiropteran Calca, with Comments on the Phylogenetic Relationships of ''Archaeopteropus''|s2cid=20426664}}</ref> The entire leg is rotated at the hip compared to normal mammal orientation, meaning that the knees face [[Anatomical terms of location#Anterior and posterior|posteriorly]]. All five digits of the foot flex in the direction of the [[sagittal plane]], with no digit capable of flexing in the opposite direction, as in the feet of perching birds.<ref name="Bennett">{{cite journal|doi=10.1111/j.1469-7998.1993.tb02633.x|title=Structural modifications involved in the fore- and hind limb grip of some flying foxes (Chiroptera: Pteropodidae)|journal=[[Journal of Zoology]]|volume=229|issue=2|pages=237–248|year=1993|last1=Bennett|first1=M. B.}}</ref>

===Internal systems===
[[File:Hypsignathus monstrosus anatomy.png|thumb|alt=A scientific illustration of the internal anatomy of a megabat. Its organs are individually labeled.|Internal anatomy of the [[hammer-headed bat]] (''Hypsignathus monstrosus'')]]
Flight is very energetically expensive, requiring several adaptations to the [[cardiovascular system]]. During flight, bats can raise their [[oxygen consumption]] by twenty times or more for sustained periods; human athletes can achieve an increase of a factor of twenty for a few minutes at most.<ref name="Maina">{{cite journal|url=http://jeb.biologists.org/content/jexbio/111/1/43.full.pdf| title=Correlations between structure and function in the design of the bat lung: a morphometric study| first1=J. N.| last1= Maina| first2= A. S.| last2= King| journal=[[Journal of Experimental Biology]]| year= 1984| volume= 11| issue=1| page=44| doi=10.1242/jeb.111.1.43| bibcode=1984JExpB.111...43M}}</ref> A 1994 study of the [[straw-coloured fruit bat]] (''Eidolon helvum'') and [[hammer-headed bat]] (''Hypsignathus monstrosus'') found a mean [[respiratory exchange ratio]] (carbon dioxide produced:oxygen used) of approximately 0.78. Among these two species, the [[gray-headed flying fox]] (''Pteropus poliocephalus'') and the [[Egyptian fruit bat]] (''Rousettus aegyptiacus''), maximum heart rates in flight varied between 476 beats per minute (gray-headed flying fox) and 728 beats per minute (Egyptian fruit bat). The maximum number of breaths per minute ranged from 163 (gray-headed flying fox) to 316 (straw-colored fruit bat).<ref>{{cite journal|url=http://jeb.biologists.org/content/jexbio/120/1/79.full.pdf| title=Flight Physiology of Intermediate-Sized Fruit Bats (Pteropodidae)| journal=Journal of Experimental Biology|year= 1986| volume= 120| pages= 84–93|first=R. E.| last=Carpenter| issue=1| doi=10.1242/jeb.120.1.79| bibcode=1986JExpB.120...79C}}</ref> Additionally, megabats have exceptionally large [[lung volumes]] relative to their sizes. While terrestrial mammals such as [[shrew]]s have a lung volume of 0.03&nbsp;cm<sup>3</sup> per gram of body weight (0.05&nbsp;in<sup>3</sup> per ounce of body weight), species such as the [[Wahlberg's epauletted fruit bat]] (''Epomophorus wahlbergi'') have lung volumes 4.3 times greater at 0.13&nbsp;cm<sup>3</sup> per gram (0.22&nbsp;in<sup>3</sup> per ounce).<ref name="Maina"/>

Megabats have rapid digestive systems, with a gut transit time of half an hour or less.<ref name="Nelson">{{cite report|url=https://www.environment.gov.au/system/files/pages/a117ced5-9a94-4586-afdb-1f333618e1e3/files/37-ind.pdf| title=Fauna of Australia| last=Nelson| first=J. E.| volume=1B|publisher=[[Department of the Environment and Energy|Australian Government Department of the Environment and Energy]]}}</ref> The digestive system is structured to a [[herbivorous]] diet sometimes restricted to soft fruit or nectar.<ref name="Richards1983" /> The length of the digestive system is short for a herbivore (as well as shorter than those of [[insectivorous]] microchiropterans),<ref name="Richards1983"/> as the fibrous content is mostly separated by the action of the palate, tongue, and teeth, and then discarded.<ref name="Richards1983" /> Many megabats have U-shaped stomachs. There is no distinct difference between the small and large intestine, nor a distinct beginning of the [[rectum]]. They have very high densities of intestinal [[microvillus|microvilli]], which creates a large surface area for the absorption of nutrients.<ref>{{cite book| title=Comparative Anatomy of the Gastrointestinal Tract in Eutheria II| editor-first=A.| editor-last= Schmidt-Rhaesa| isbn=9783110560671| publisher=[[Walter de Gruyter GmbH & Co KG]]| year=2017|pages=328–330}}</ref>