Editing Turtle (section)

===Internal relationships===
Modern turtles and their extinct relatives with a complete shell are classified within the clade [[Testudinata]].<ref>{{Cite journal |last1=Joyce |first1=Walter G. |last2=Anquetin |first2=Jérémy |last3=Cadena |first3=Edwin-Alberto |last4=Claude |first4=Julien |last5=Danilov |first5=Igor G. |last6=Evers |first6=Serjoscha W. |last7=Ferreira |first7=Gabriel S. |last8=Gentry |first8=Andrew D. |last9=Georgalis |first9=Georgios L. |last10=Lyson |first10=Tyler R. |last11=Pérez-García |first11=Adán |date=December 2021 |title=A Nomenclature for Fossil and Living Turtles Using Phylogenetically Defined Clade Names |journal=[[Swiss Journal of Palaeontology]] |language=en |volume=140 |issue=1 |pages=5 |doi=10.1186/s13358-020-00211-x |s2cid=229506832 |issn=1664-2376 |doi-access=free|bibcode=2021SwJP..140....5J |hdl=11336/155192 |hdl-access=free }}</ref> The most recent common ancestor of living turtles, corresponding to the split between Pleurodira (side-necked species) and [[Cryptodira]] (hidden necked species), is estimated to have occurred around {{Ma|210}} during the Late Triassic.<ref>{{cite journal |last1=Böhmer |first1=Christine |last2=Werneburg |first2=Ingmar |year=2017 |title=Deep Time Perspective on Turtle Neck Evolution: Chasing the ''Hox'' Code by Vertebral Morphology |journal=Scientific Reports |volume=7 |issue=1 |page=8939 |doi=10.1038/s41598-017-09133-0|pmid=28827543 |pmc=5566328 |bibcode=2017NatSR...7.8939B }}</ref> Robert Thompson and colleagues (2021) comment that living turtles have low diversity, relative to how long they existed. Diversity has been stable, according to their analysis, except for a single rapid increase around the [[Eocene-Oligocene boundary]] some 30 million years ago, and a large regional extinction at roughly the same time. They suggest that global climate change caused both events, as the cooling and drying caused the land to become arid and turtles to become extinct there, while new continental margins opened up by the climate change provided habitats for other species to evolve.<ref name="Thomson Spinks Shaffer 2021">{{cite journal |last1=Thomson |first1=Robert C. |last2=Spinks |first2=Phillip Q. |last3=Shaffer |first3=H. Bradley |title=A Global Phylogeny of Turtles Reveals a Burst of Climate-associated Diversification on Continental Margins |journal=Proceedings of the National Academy of Sciences |volume=118 |issue=7 |date=February 8, 2021 |issn=0027-8424 |doi=10.1073/pnas.2012215118 |page=e2012215118 |pmid=33558231 |pmc=7896334 |bibcode=2021PNAS..11812215T |doi-access=free }}</ref>

The cladogram, from Nicholas<!--2nd use--> Crawford and colleagues 2015, shows the internal phylogeny of the Testudines down to the level of [[Family (biology)|families]].<ref name="Crawford Parham 2015">{{cite journal |last1=Crawford |first1=Nicholas G. |last2=Parham |first2=James F. |last3=Sellas |first3=Anna B. |last4=Faircloth |first4=Brant C. |last5=Glenn |first5=Travis C. |last6=Papenfuss |first6=Theodore J. |last7=Henderson |first7=James B. |last8=Hansen |first8=Madison H. |last9=Simison |first9=W. Brian |title=A Phylogenomic Analysis of Turtles |journal=Molecular Phylogenetics and Evolution |volume=83 |year=2015 |pages=250–257 |issn=1055-7903 |doi=10.1016/j.ympev.2014.10.021|pmid=25450099 }}</ref><ref name="Knauss Joyce Lyson Pearson pp. 125–142"><!--for Chelydroidea-->{{cite journal |last1=Knauss |first1=Georgia E. |last2=Joyce |first2=Walter G. |last3=Lyson |first3=Tyler R. |last4=Pearson |first4=Dean |title=A New Kinosternoid from the Late Cretaceous Hell Creek Formation of North Dakota and Montana and the Origin of the ''Dermatemys mawii'' Lineage |journal=Paläontologische Zeitschrift |publisher=Springer Science and Business Media LLC |volume=85 |issue=2 |date=September 21, 2010 |issn=0031-0220 |doi=10.1007/s12542-010-0081-x |pages=125–142|s2cid=129123961 }}</ref> The analysis by <!--Robert--> Thompson and colleagues in 2021 supports the same structure down to the family level.<ref name="Thomson Spinks Shaffer 2021"/>

{{clade
|label1='''Testudines'''
|1={{clade
   |label1=[[Pleurodira]]
   |sublabel1='' (Side-necked turtles) ''
   |1={{clade
      |1={{clade <!--extra dummy clade-->
         |label1=[[Chelidae]]
         |1=[[File:Erpétologie générale, ou, Histoire naturelle complète des reptiles (Chelus fimbriata).jpg|70px]]
         }}
      |2={{clade
         |label1=[[Pelomedusidae]]
         |1=[[File:Erpétologie générale, ou, Histoire naturelle complète des reptiles (Pelomedusa subrufa).jpg|70px]]
         |label2=[[Podocnemididae]]
         |2=[[File:Erpétologie générale, ou, Histoire naturelle complète des reptiles (Podocnemis expansa).jpg|70px]]
         }}
      }}
   |label2=[[Cryptodira]]
   |sublabel2='' (Hidden-necked turtles) ''
   |2={{clade
      |1={{clade
         |label1=[[Trionychia]]
         |sublabel1='' (Softshell turtles) ''
         |1={{clade
            |label1=[[Carettochelyidae]] 
            |sublabel1='' (Pig-nosed turtle) ''
            |1=[[File:Pig-nosed turtle (Carettochelys insculpta) (cropped).jpg|65px]]
            |label2=[[Trionychidae]]
            |2=[[File:Erpétologie générale, ou, Histoire naturelle complète des reptiles (Lissemys punctata).jpg|65px]]
            }}
         }}
      |2={{clade <!--extra dummy clade-->
         |label1=<!--Durocryptodira--Crawford 2015-->
         |sublabel1='' (Hardshell turtles) ''
         |1={{clade
            |1={{clade
               |label1=[[Testudinoidea]]
               |1={{clade
                  |1={{clade
                     |label1=[[Emydidae]]
                     |sublabel1='' (Terrapins) ''
                     |1=[[File:Emydoidea blandingiiHolbrookV1P03A flipped.jpg|70px]]
                     |label2=[[Platysternidae]] 
                     |2=[[File:Erpétologie générale, ou, Histoire naturelle complète des reptiles (Platysternon megacephalum).jpg|70px]]
                     }}
                  |2={{clade
                     <!--|sublabel1=''Pond, river, & wood turtles''-->
                     |label1=[[Geoemydidae]] 
                     |1=[[File:Erpétologie générale, ou, Histoire naturelle complète des reptiles (Morenia ocellata).jpg|70px]]
                     |label2=[[Testudinidae]]
                     |sublabel2='' (Tortoises) ''
                     |2=[[File:Erpétologie générale, ou, Histoire naturelle complète des reptiles (Centrochelys sulcata).jpg|70px]]
                     }}
                  }}
               }}
            |2={{clade
               |label1=[[Chelonioidea]]
               |sublabel1='' (Sea turtles) ''
               |1={{clade
                  |label1=[[Cheloniidae]]
                  |1=&nbsp;[[File:Erpétologie générale, ou, Histoire naturelle complète des reptiles (Chelonia mydas).jpg|90px]]
                  |label2=[[Dermochelyidae]]
                  |sublabel2='' (Leatherback) ''
                  |2=&nbsp;[[File:Erpétologie générale, ou, Histoire naturelle complète des reptiles (Dermochelys coriacea).jpg|90px]]
                  }}
               |label2=[[Chelydroidea]]<!--Crawford 2015-->
               |2={{clade
                  |1={{clade <!--extra dummy clade-->
                     |label1=[[Chelydridae]]
                     |1=[[File:Erpétologie générale, ou, Histoire naturelle complète des reptiles (Chelydra serpentina).jpg|70px]]
                     |sublabel1='' (Snapping turtles) ''
                     }}
                  |label2x=[[Kinosternoidea]] <!-- Reptile DB now uses Chelydroidea -->
                  |2={{clade
                     |label1=[[Dermatemydidae]]
                     |1=[[File:ChloremysAbnormisFord white background.jpg|70px]]
                     |label2=[[Kinosternidae]]
                     |2=[[File:Erpétologie générale, ou, Histoire naturelle complète des reptiles (Sternotherus odoratus).jpg|70px]]
                     }}
                  }}
               }}
            }}
         }}
      }}
   }}
}}