Editing Chameleon (section)

==Evolution==
[[File:Erpétologie générale, ou, Histoire naturelle complète des reptiles (Chamaeleo chamaeleon skeleton).jpg|thumb|Skeleton of [[common chameleon]]]]
The oldest described chameleon is ''[[Anqingosaurus|Anqingosaurus brevicephalus]]'' from the Middle Paleocene (about 58.7–61.7 [[mya (unit)|mya]]) of China.<ref name="Digimorph">{{cite web |url=http://www.digimorph.org/specimens/Chamaeleo_calyptratus/whole |work=Digimorph |publisher=University of Texas at Austin |title=Chamaeleo calyptratus, Veiled Chameleon |date=27 August 2003 |access-date=January 10, 2012 |author=Maisano, Jessie}}</ref>
Other chameleon fossils include ''[[Chamaeleo caroliquarti]]'' from the Lower Miocene (about 13–23 mya) of the Czech Republic and Germany, and ''Chamaeleo intermedius'' from the Upper Miocene (about 5–13 mya) of Kenya.<ref name=" Digimorph"/>

The chameleons are probably far older than that, perhaps sharing a common ancestor with [[Iguanidae|iguanids]] and [[agamids]] more than 100 mya (agamids being more closely related). Since fossils have been found in Africa, Europe, and Asia, chameleons were certainly once more widespread than they are today.

Although nearly half of all chameleon species today live in Madagascar, this offers no basis for speculation that chameleons might originate from there.<ref>{{cite book |last1=Tolley |first1=Krystal |last2=Burger |first2=Marius |year=2007 |title=Chameleons of Southern Africa |publisher=Struik |isbn=978-1-77007-375-3 |pages=26–28}}</ref> In fact, it has recently been shown that chameleons most likely originated in mainland Africa.<ref name=" Tolley et al. 2013" /> It appears there were two distinct oceanic migrations from the mainland to Madagascar. The diverse speciation of chameleons has been theorized to have directly reflected the increase in open habitats (savannah, grassland, and heathland) that accompanied the Oligocene period. [[Monophyly]] of the family is supported by several studies.<ref>{{cite book|chapter-url=https://books.google.com/books?id=ylUlDQAAQBAJ&q=chameleon+monophyly&pg=PA179|chapter=Fossil History of Chameleons|vauthors= Bolet A, Evans SE|title=The Biology of Chameleons|editor-first1=Krystal A.|editor-last1=Tolley|editor-first2=Anthony|editor-last2=Herrel|date=16 November 2013|publisher=Univ of California Press|access-date=1 November 2017|via=Google Books|isbn=9780520276055}}</ref>

Daza ''et al.'' (2016) described a small (10.6&nbsp;mm in snout-vent length), probably [[neonatal]] lizard preserved in the Cretaceous ([[Albian]]-[[Cenomanian]] boundary) amber from [[Myanmar]]. The authors noted that the lizard has "short and wide skull, large orbits, elongated and robust lingual process, frontal with parallel margins, incipient prefrontal boss, reduced vomers, absent retroarticular process, low presacral vertebral count (between 15 and 17) and extremely short, curled tail"; the authors considered these traits to be indicative of the lizard's affiliation with Chamaeleonidae. The phylogenetic analysis conducted by the authors indicated that the lizard was a [[Crown group#Stem groups|stem]]-chamaeleonid.<ref>{{Cite journal|last1=Daza |first1=Juan D. |last2=Stanley |first2=Edward L. |author3=Wagner, Philipp |author4=Bauer, Aaron M. |author5=Grimaldi, David A.|display-authors=3 |year=2016 |title=Mid-Cretaceous amber fossils illuminate the past diversity of tropical lizards |journal=Science Advances |volume=2 |issue=3 |pages=e1501080 |doi=10.1126/sciadv.1501080 |pmid=26973870 |bibcode=2016SciA....2E1080D|pmc=4783129 }}</ref> However, Matsumoto & [[Susan E. Evans|Evans]] (2018) reinterpreted this specimen as an [[Albanerpetontidae|albanerpetontid]] amphibian.<ref>{{Cite journal|author1=Ryoko Matsumoto |author2=Susan E. Evans |year=2018 |title=The first record of albanerpetontid amphibians (Amphibia: Albanerpetontidae) from East Asia |journal=PLOS ONE |volume=13 |issue=1 |pages=e0189767 |doi=10.1371/journal.pone.0189767 |pmid=29298317 |pmc=5752013 |bibcode=2018PLoSO..1389767M |doi-access=free }}</ref> This specimen was given the name ''[[Yaksha perettii]]'' in 2020, and was noted to have several convergently chameleon-like features, including adaptations for ballistic feeding.<ref>{{Cite journal|last1=Daza|first1=Juan D.|last2=Stanley|first2=Edward L.|last3=Bolet|first3=Arnau|last4=Bauer|first4=Aaron M.|last5=Arias|first5=J. Salvador|last6=Čerňanský|first6=Andrej|last7=Bevitt|first7=Joseph J.|last8=Wagner|first8=Philipp|last9=Evans|first9=Susan E.|display-authors=3|date=2020-11-06|title=Enigmatic amphibians in mid-Cretaceous amber were chameleon-like ballistic feeders|url=https://www.science.org/doi/10.1126/science.abb6005|journal=Science|language=en|volume=370|issue=6517|pages=687–691|doi=10.1126/science.abb6005|issn=0036-8075|pmid=33154135|bibcode=2020Sci...370..687D|s2cid=226254862}}</ref>
[[File:Nice chameleon portrait.jpg|thumb|315x315px|Chameleon in Ghana]]
While the exact evolutionary history of colour change in chameleons is still unknown, there is one aspect of the evolutionary history of chameleon colour change that has already been conclusively studied: the effects of signal efficacy. Signal efficacy, or how well the signal can be seen against its background, has been shown to correlate directly to the spectral qualities of chameleon displays.<ref name=signals>{{cite journal |last1=Stuart-Fox |first1=D. |last2=Moussalli |first2=Adnan |last3=Whiting |first3=Martin J. |year=2007 |title=Natural Selection on Social Signals: Signal Efficacy and the Evolution of Chameleon Display coloration |doi=10.1086/522835 |pmid=18171173 |journal=The American Naturalist |volume=170 |issue=6|pages=916–930 |s2cid=21716855 |url=http://www.researchonline.mq.edu.au/vital/access/services/Download/mq:15515/DS01 }}</ref> Dwarf chameleons, the chameleon of study, occupy a wide variety of habitats from forests to grasslands to shrubbery. It was demonstrated that chameleons in brighter areas tended to present brighter signals, but chameleons in darker areas tended to present relatively more contrasting signals to their backgrounds. This finding suggests that signal efficacy (and thus habitat) has affected the evolution of chameleon signaling. Stuart-Fox et al. note that it makes sense that selection for crypsis is not seen to be as important as selection for signal efficacy, because the signals are only shown briefly; chameleons are almost always muted cryptic colours.<ref name=signals />