Editing Turtle (section)

=== Fossil history===
[[File:Origin of Turtle Body Plan.jpg|thumb|upright=1.2|Diagram of the origins of the turtle body plan through the [[Triassic]]: isolated bony plates evolved to [[Turtle shell#Origins|form a complete shell]], in a sequence involving ''[[Pappochelys]]'', ''[[Eorhynchochelys]]'', ''[[Odontochelys]]'', and ''[[Proganochelys]]''.<ref name="Schoch Sues 2019"/>|alt=Diagram of evolution of turtle shells showing four fossil species]]

Zoologists have sought to explain the evolutionary origin of the turtles, and in particular of their unique shells. In 1914, [[Jan Versluys]] proposed that bony plates in the dermis, called [[osteoderm]]s, fused to the ribs beneath them, later called the "Polka Dot Ancestor" by Olivier Rieppel.<ref name="Schoch Sues 2019"/><ref>{{Cite book |title=Turtles as Hopeful Monsters: Origins and Evolution<!--what a title, but Rieppel is ok actually--> |last=Rieppel |first=Olivier |isbn=978-0-253-02507-4 |publisher=Indiana University Press |page=195 |oclc=962141060 |year=2017}}</ref> The theory accounted for the evolution of fossil [[pareiasaur]]s from ''[[Bradysaurus]]'' to ''[[Anthodon (reptile)|Anthodon]]'', but not for how the ribs could have become attached to the bony dermal plates.<ref name="Schoch Sues 2019">{{cite journal |last1=Schoch |first1=Rainer R. |last2=Sues |first2=Hans-Dieter |last3=Benson |first3=Roger |title=The Origin of the Turtle Body Plan: Evidence from Fossils and Embryos |journal=Palaeontology |volume=63 |issue=3 |year=2019 |pages=375–393 |issn=0031-0239 |doi=10.1111/pala.12460 |doi-access=free }}</ref>

More recent discoveries have painted a different scenario for the evolution of the turtle's shell. The [[Crown group#Stem groups|stem]]-turtles ''[[Eunotosaurus]]'' of the Middle [[Permian]], ''[[Pappochelys]]'' of the [[Middle Triassic]], and ''[[Eorhynchochelys]]'' of the [[Late Triassic]] lacked carapaces and plastrons but had shortened torsos, expanded ribs, and lengthened dorsal vertebrae. Also in the Late Triassic, ''[[Odontochelys]]'' had a partial shell consisting of a complete bony plastron and an incomplete carapace. The development of a shell reached completion with the Late Triassic ''[[Proganochelys]]'', with its fully developed carapace and plastron.<ref name="Schoch Sues 2019"/><ref name="Lyson2020"/> Adaptations that led to the evolution of the shell may have originally been for digging and a [[fossorial]] lifestyle.<ref name="Lyson2020">{{cite journal |last1=Lyson |first1=Tyler R. |last2=Bever |first2=Gabriel S. |year=2020 |title=Origin and Evolution of the Turtle Body Plan |journal=Annual Review of Ecology, Evolution, and Systematics |volume=51 |issue=1 |pages=143–166 |doi=10.1146/annurev-ecolsys-110218-024746 |s2cid=225486775|doi-access=free }}</ref>

The oldest known members of the Pleurodira lineage are the [[Platychelyidae]], from the [[Late Jurassic]].<ref name=":02">{{Cite journal|last1=Cadena|first1=Edwin|last2=Joyce|first2=Walter G.|date=April 2015|title=A Review of the Fossil Record of Turtles of the Clades Platychelyidae and Dortokidae|url=http://www.bioone.org/doi/10.3374/014.056.0101|journal=Bulletin of the Peabody Museum of Natural History|language=en|volume=56|issue=1|pages=3–20|doi=10.3374/014.056.0101|s2cid=56195415|issn=0079-032X}}</ref> The oldest known unambiguous cryptodire is ''[[Sinaspideretes]],'' a close relative of softshell turtles, from the Late Jurassic of China.<ref>{{Cite journal|last1=Evers|first1=Serjoscha W.|last2=Benson|first2=Roger B. J.|date=January 2019|editor-last=Smith|editor-first=Andrew|title=A new phylogenetic hypothesis of turtles with implications for the timing and number of evolutionary transitions to marine lifestyles in the group|url=https://onlinelibrary.wiley.com/doi/10.1111/pala.12384|journal=Palaeontology|language=en|volume=62|issue=1|pages=93–134|doi=10.1111/pala.12384|bibcode=2019Palgy..62...93E |s2cid=134736808}}</ref> Turtles became highly diverse during the Cretaceous, as climatic conditions in this period were favourable for their global dispersal.<ref>{{Cite journal |last1=Nicholson |first1=David B. |last2=Holroyd |first2=Patricia A. |last3=Benson |first3=Roger B. J. |last4=Barrett |first4=Paul M. |date=3 August 2015 |title=Climate-mediated diversification of turtles in the Cretaceous |journal=[[Nature Communications]] |language=en |volume=6 |issue=1 |pages=7848 |doi=10.1038/ncomms8848 |pmid=26234913 |pmc=4532850 |issn=2041-1723 }}</ref> During the [[Late Cretaceous]] and [[Cenozoic]], members of the pleurodire families [[Bothremydidae]] and [[Podocnemididae]] became widely distributed in the Northern Hemisphere due to their coastal habits.<ref>{{Cite journal |last=Pérez-García |first=Adán |date=September 2, 2017 |title=A new Turtle Taxon (Podocnemidoidea, Bothremydidae) Reveals the Oldest Known Dispersal Event of the Crown Pleurodira from Gondwana to Laurasia |url=https://www.tandfonline.com/doi/full/10.1080/14772019.2016.1228549 |journal=Journal of Systematic Palaeontology |volume=15 |issue=9 |pages=709–731 |doi=10.1080/14772019.2016.1228549 |bibcode=2017JSPal..15..709P |s2cid=88840423 |issn=1477-2019}}</ref><ref>{{Cite journal |last1=Ferreira |first1=Gabriel S. |last2=Bandyopadhyay |first2=Saswati |last3=Joyce |first3=Walter G. |date=November 15, 2018 |title=A Taxonomic Reassessment of Piramys auffenbergi, a Neglected Turtle from the late Miocene of Piram Island, Gujarat, India |journal=PeerJ |language=en |volume=6 |pages=e5938 |doi=10.7717/peerj.5938 |pmid=30479901 |pmc=6240434|issn=2167-8359 |doi-access=free }}</ref> The oldest known soft-shelled turtles and sea turtles appeared during the [[Early Cretaceous]].<ref>{{cite book |last1=Hirayama |first1=Ren |title=Kappachelys okurai gen. et sp. nov., a New Stem Soft-Shelled Turtle from the Early Cretaceous of Japan |date=2013 |url=http://link.springer.com/10.1007/978-94-007-4309-0_12 |work=Morphology and Evolution of Turtles |pages=179–185 |editor-last=Brinkman |editor-first=Donald B. |place=Dordrecht |publisher=Springer Netherlands |doi=10.1007/978-94-007-4309-0_12 |isbn=978-94-007-4308-3 |last2=Isaji |first2=Shinji |last3=Hibino |first3=Tsuyoshi |series=Vertebrate Paleobiology and Paleoanthropology |editor2-last=Holroyd |editor2-first=Patricia A. |editor3-last=Gardner |editor3-first=James D.}}</ref><ref>{{Cite journal |last1=Evers |first1=Serjoscha W. |last2=Barrett |first2=Paul M. |last3=Benson |first3=Roger B. J. |date=May 2019 |title=Anatomy of Rhinochelys pulchriceps (Protostegidae) and Marine Adaptation During the Early Evolution of chelonioids |journal=PeerJ |volume=7 |pages=e6811 |doi=10.7717/peerj.6811 |pmid=31106054 |pmc=6500378 |issn=2167-8359 |doi-access=free }}</ref> Tortoises originated in Asia during the [[Eocene]].<ref>{{Cite journal |last1=Hofmeyr |first1=Margaretha D. |last2=Vamberger |first2=Melita |last3=Branch |first3=William |last4=Schleicher |first4=Alfred |last5=Daniels |first5=Savel R. |date=July 2017 |title=Tortoise (Reptilia, Testudinidae) Radiations in Southern Africa from the Eocene to the Present |url=http://doi.wiley.com/10.1111/zsc.12223|journal=Zoologica Scripta |volume=46 |issue=4 |pages=389–400 |doi=10.1111/zsc.12223 |s2cid=88712318}}</ref> A late surviving group of stem-turtles, the [[Meiolaniidae]], survived in Australasia into the [[Pleistocene]] and [[Holocene]].<ref>{{Cite journal |last1=Poropat |first1=Stephen F. |last2=Kool |first2=Lesley |last3=Vickers-Rich |first3=Patricia |last4=Rich |first4=Thomas H. |date=April 3, 2017 |title=Oldest Meiolaniid Turtle Remains from Australia: Evidence from the Eocene Kerosene Creek Member of the Rundle Formation, Queensland |url=https://www.tandfonline.com/doi/full/10.1080/03115518.2016.1224441 |journal=Alcheringa: An Australasian Journal of Palaeontology |volume=41 |issue=2 |pages=231–239 |doi=10.1080/03115518.2016.1224441 |bibcode=2017Alch...41..231P |s2cid=131795055 |issn=0311-5518}}</ref>