Editing Turtle (section)

=== External relationships===
<!--[[File:Haeckel Chelonia.jpg|thumb|upright|"Chelonia" from [[Ernst Haeckel]]'s ''[[Kunstformen der Natur]]'', 1904 |alt=Historic painting of examples of different families of turtles ]]-->

The turtles' exact ancestry has been disputed. It was believed they were the only surviving branch of the ancient [[evolutionary grade]] [[Anapsid]]a, which includes groups such as [[Procolophonidae|procolophonid]]s and pareiasaurs. All anapsid skulls lack a [[Temporal fenestra|temporal opening]] while all other living amniotes have temporal openings.<ref name="Rieppel">{{cite journal |last1=Rieppel |first1=Olivier |year=1996 |last2=DeBraga |first2=M. |title=Turtles as Diapsid Reptiles |journal=Nature |volume=384 |issue=6608 |pages=453–455 |doi=10.1038/384453a0 |bibcode=1996Natur.384..453R |s2cid=4264378 |url=http://doc.rero.ch/record/16242/files/PAL_E3477.pdf }}</ref> It was later suggested that the anapsid-like turtle skulls may be due to [[backward evolution]] rather than to anapsid descent.<ref name="Zardoya">{{Cite journal |last1=Zardoya |first1=Rafael |last2=Meyer |first2=Axel |title=Complete Mitochondrial Genome Suggests Diapsid Affinities of Turtles |year=1998 |journal=PNAS |volume=95 |issue=24 |pages=14226–14231 |issn=0027-8424 |doi=10.1073/pnas.95.24.14226 |pmid=9826682 |pmc=24355 |bibcode=1998PNAS...9514226Z |url=https://kops.uni-konstanz.de/bitstream/123456789/6719/1/Complete_mitochondrial_genome_1998.pdf |access-date=October 31, 2018 |archive-date=July 24, 2021 |archive-url=https://web.archive.org/web/20210724105253/https://kops.uni-konstanz.de/bitstream/handle/123456789/6719/Complete_mitochondrial_genome_1998.pdf;jsessionid=CDA4382393A7DA330520DCB828E8B86D?sequence=1 |url-status=live|doi-access=free }}</ref> Fossil evidence has shown that early stem-turtles possessed small temporal openings.<ref name="Lyson2020"/>

Some early morphological [[phylogenetics|phylogenetic]] studies have placed turtles closer to [[Lepidosauria]] ([[tuatara]]s, [[lizard]]s, and [[snake]]s) than to [[Archosaur]]ia ([[crocodilian]]s and birds).<ref name="Rieppel"/> By contrast, several [[Molecular phylogenetics|molecular]] studies place turtles either within Archosauria,<ref name="Mannen">{{Cite journal |last1=Mannen |first1=Hideyuki |last2=Li |first2=Steven S.-L. |title=Molecular Evidence for a Clade of Turtles |date=October 1999 |journal=Molecular Phylogenetics and Evolution |volume=13 |issue=1 |pages=144–148 |doi=10.1006/mpev.1999.0640 |pmid=10508547 }}</ref> or, more commonly, as a [[sister group]] to extant archosaurs,<ref name="Zardoya"/><ref name="Iwabe">{{Cite journal |last1=Iwabe |first1=Naoyuki |last2=Hara |first2=Yuichiro |last3=Kumazawa |first3=Yoshinori |last4=Shibamoto |first4=Kaori |last5=Saito |first5=Yumi |last6=Miyata |first6=Takashi |last7=Katoh |first7=Kazutaka |title=Sister Group Relationship of Turtles to the Bird-Crocodilian Clade Revealed by Nuclear DNA-coded Proteins |date=December 2004 |journal=Molecular Biology and Evolution |volume=22 |issue=4 |pages=810–813 |doi=10.1093/molbev/msi075 |pmid=15625185  |doi-access=free}}</ref><ref name="Roos">{{Cite journal |last1=Roos |first1=Jonas |last2=Aggarwal |first2=Ramesh K. |last3=Janke |first3=Axel |title=Extended Mitogenomic Phylogenetic Analyses Yield new Insight into Crocodylian Evolution and Their Survival of the Cretaceous–Tertiary Boundary |journal=[[Molecular Phylogenetics and Evolution]] |volume=45 |issue=2 |pages=663–673 |date=November 2007  |doi=10.1016/j.ympev.2007.06.018 |pmid=17719245 }}</ref><ref name="Katsu">{{Cite journal |last1=Katsu |first1=Yoshinao |date=March 2010 |last2=Braun |first2=Edward L. |last3=Guillette |first3=Louis J. Jr. |last4=Iguchi |first4=Taisen |title=From Reptilian Phylogenomics to Reptilian Genomes: Analyses of c-Jun and DJ-1 Proto-oncogenes |journal=Cytogenetic and Genome Research |volume=127 |issue=2–4 |pages=79–93 |doi=10.1159/000297715 |pmid=20234127 |s2cid=12116018}}</ref> though an analysis conducted by Tyler Lyson and colleagues (2012) recovered turtles as the sister group of lepidosaurs instead.<ref>{{Cite journal |last1=Lyson |first1=Tyler R. |last2=Sperling |first2=Erik A. |last3=Heimberg |first3=Alysha M. |last4=Gauthier |first4=Jacques A. |last5=King |first5=Benjamin L. |last6=Peterson |first6=Kevin J. |title=MicroRNAs Support a Turtle + Lizard Clade |year=2012 |journal=[[Biology Letters]] |volume=8 |issue=1 |pages=104–107 |doi=10.1098/rsbl.2011.0477 |pmid=21775315 |pmc=3259949}}</ref> Ylenia Chiari and colleagues (2012) analyzed 248 [[nuclear gene]]s from 16 vertebrates and suggested that turtles share a [[most recent common ancestor|more recent common ancestor]] with birds and crocodilians. The date of separation of turtles and birds and crocodilians was estimated to be {{Ma|255}} during the Permian.<ref name="Chiari2012">{{Cite journal |last1=Chiari |first1=Ylenia |year=2012 |last2=Cahais |first2=Vincent |last3=Galtier |first3=Nicolas |last4=Delsuc |first4= Frédéric |title=Phylogenomic Analyses Support the Position of Turtles as the Sister Group of Birds and Crocodiles (Archosauria) |journal=BMC Biology |volume=10 |issue=65 |page=65 |doi=10.1186/1741-7007-10-65 |pmid=22839781 |pmc=3473239 |doi-access=free }}</ref> Through [[genomic]]-scale phylogenetic study of [[ultra-conserved element]]s (UCEs) to clarify the placement of turtles within reptiles, Nicholas Crawford and colleagues (2012) similarly found that turtles are closer to birds and crocodilians.<ref name="Crawford 2012">{{Cite journal |year=2012 |last1=Crawford |first1=Nicholas G. |last2=Faircloth |first2=Brant C. |last3=McCormack |first3=John E. |last4=Brumfield |first4=Robb T. |last5=Winker |first5=Kevin |last6=Glen |first6=Travis C. |title=More than 1000 Ultraconserved Elements Provide Evidence that Turtles are the Sister Group to Archosaurs |journal=Biology Letters |volume=8 |issue=5 |pages=783–786 |url=http://faculty.oxy.edu/mccormack/McCormack/picks/Crawford_2012_BioLett.pdf |access-date=September 21, 2014 |doi=10.1098/rsbl.2012.0331 |pmid=22593086 |pmc=3440978 |archive-date=August 10, 2012 |archive-url=https://web.archive.org/web/20120810100341/http://faculty.oxy.edu/mccormack/McCormack/picks/Crawford_2012_BioLett.pdf |url-status=live }}</ref>

Using the draft (unfinished) genome sequences of the green sea turtle and the [[Chinese softshell turtle]], Zhuo Wang and colleagues (2013) concluded that turtles are likely a sister group of crocodilians and birds.<ref name="Wang 2013">{{cite journal |doi=10.1038/ng.2615 |pmid=23624526 |pmc=4000948 |title=The Draft Genomes of Soft-shell Turtle and Green Sea Turtle Yield Insights into the Development and Evolution of the Turtle-specific Body Plan |journal=Nature Genetics |volume=45 |issue=6 |pages=701–706 |year=2013 |last1=Wang |first1=Zhuo |last2=Pascual-Anaya |first2=Juan |last3=Zadissa |first3=Amonida |last4=Li |first4=Wenqi |last5=Niimura |first5=Yoshihito |last6=Huang |first6=Zhiyong |last7=Li |first7=Chunyi |last8=White |first8=Simon |last9=Xiong |first9=Zhiqiang |last10=Fang |first10=Dongming |last11=Wang |first11=Bo |last12=Ming |first12=Yao |last13=Chen |first13=Yan |last14=Zheng |first14=Yuan |last15=Kuraku |first15=Shigehiro |last16=Pignatelli |first16=Miguel |last17=Herrero |first17=Javier |last18=Beal |first18=Kathryn |last19=Nozawa |first19=Masafumi |last20=Li |first20=Qiye |last21=Wang |first21=Juan |last22=Zhang |first22=Hongyan |last23=Yu |first23=Lili |last24=Shigenobu |first24=Shuji |last25=Wang |first25=Junyi |last26=Liu |first26=Jiannan |last27=Flicek |first27=Paul |last28=Searle |first28=Steve |last29=Wang |first29=Jun |last30=Kuratani |first30=Shigeru |display-authors=3}}</ref> The external phylogeny of the turtles is shown in the [[cladogram]] below.<ref name="Crawford 2012"/>

{{clade
|label1=[[Diapsida]]
|1={{clade
   |label1=[[Lepidosauromorpha]]
   |1=[[Squamata]] (lizards, snakes) [[File:Zoology of Egypt (1898) (Varanus exanthematicus).png|70px]]
   |label2=[[Archosauromorpha]]
   |2={{clade
      |1='''Testudines''' [[File:Psammobates geometricus 1872 white background.jpg|60px]]
      |2={{clade
         |1=[[Crocodilia]] (crocodiles, alligators) <span style="{{MirrorH}}">[[File:Deinosuchus riograndensis.png|100px]]</span>
         |2=[[Aves]] (birds) [[File:Spot-billed pelican takeoff white background.jpg|80px]]
         }}
      }}
   }}
}}