Editing Shark (section)

=== Fossil record ===
[[File:+Fossiler Haifischzahn - Größe über 9 cm - mit Krone - Schulter - Wurzel und Wurzellappen.jpg|thumb|left|Fossil shark tooth (size over {{convert|9|cm|in|abbr=in|disp=or}}) with crown, shoulder, root and root lobe]]
[[File:CretaceousSharkTeeth061812.JPG|thumb|left|alt=Photo of dozens of yellowish fossilized teeth, the teeth are of various sizes and are spread out randomly on a flat black surface.|A collection of [[Cretaceous]] [[shark teeth]]]]

The oldest [[Total group|total-group]] chondrichthyans, known as [[Acanthodii|acanthodians]] or "spiny sharks", appeared during the Early [[Silurian]], around 439 million years ago.''<ref name="Andreev-2022">{{cite journal |last1=Andreev |first1=Plamen S. |last2=Sansom |first2=Ivan J. |last3=Li |first3=Qiang |last4=Zhao |first4=Wenjin |last5=Wang |first5=Jianhua |last6=Wang |first6=Chun-Chieh |last7=Peng |first7=Lijian |last8=Jia |first8=Liantao |last9=Qiao |first9=Tuo |last10=Zhu |first10=Min |date=September 2022 |title=Spiny chondrichthyan from the lower Silurian of South China |url=https://www.nature.com/articles/s41586-022-05233-8 |journal=Nature |volume=609 |issue=7929 |pages=969–974 |doi=10.1038/s41586-022-05233-8 |pmid=36171377 |bibcode=2022Natur.609..969A |s2cid=252570103}}</ref>'' The oldest confirmed members of [[Elasmobranchii]] ''sensu lato'' (the group containing all cartilaginous fish more closely related to modern sharks and rays than to [[chimaera]]s) appeared during the [[Devonian]].<ref>{{Cite journal |last1=Frey |first1=Linda |last2=Coates |first2=Michael |last3=Ginter |first3=Michał |last4=Hairapetian |first4=Vachik |last5=Rücklin |first5=Martin |last6=Jerjen |first6=Iwan |last7=Klug |first7=Christian |date=2019-10-09 |title=The early elasmobranch Phoebodus : phylogenetic relationships, ecomorphology and a new time-scale for shark evolution |journal=Proceedings of the Royal Society B: Biological Sciences |language=en |volume=286 |issue=1912 |pages=20191336 |doi=10.1098/rspb.2019.1336 |issn=0962-8452 |pmc=6790773 |pmid=31575362}}</ref> [[Anachronistidae]], the oldest probable representatives of Euselachii, the group containing modern sharks (Selachii) and rays (Batomorphi) to the exclusion of most extinct elasmobranch groups, date to the [[Carboniferous]].<ref>{{Cite journal |last=Ginter |first=Michał |date=July 2022 |title=The biostratigraphy of Carboniferous chondrichthyans |url=https://www.lyellcollection.org/doi/10.1144/SP512-2020-91 |journal=Geological Society, London, Special Publications |language=en |volume=512 |issue=1 |pages=769–790 |doi=10.1144/SP512-2020-91 |bibcode=2022GSLSP.512..769G |s2cid=229399689 |issn=0305-8719}}</ref> Selachii and Batomorphi are suggested by some to have diverged during the [[Triassic]].<ref name="Pough-2018">{{Cite book |last1=Pough |first1=F. Harvey |title=Vertebrate Life, 10th Edition |last2=Janis |first2=Christine M. |publisher=Oxford University Press |year=2018 |isbn=9781605357218 |pages=96–103}}</ref> Fossils of the earliest true sharks may have appeared during the [[Permian]], based on remains of "[[Synechodontiformes|synechodontiforms]]" found in the Early Permian of Russia,<ref>{{Cite journal |last1=Andreev |first1=Plamen S. |last2=Cuny |first2=Gilles |date=2012-02-28 |title=New Triassic stem selachimorphs (Chondrichthyes, Elasmobranchii) and their bearing on the evolution of dental enameloid in Neoselachii |url=http://dx.doi.org/10.1080/02724634.2012.644646 |journal=Journal of Vertebrate Paleontology |volume=32 |issue=2 |pages=255–266 |doi=10.1080/02724634.2012.644646 |bibcode=2012JVPal..32..255A |s2cid=84162775 |issn=0272-4634}}</ref> but if remains of "synechodontiforms" from the Permian and Triassic are true sharks, they only had low diversity. Modern shark [[Order (biology)|orders]] first appeared during the Early Jurassic, and during the Jurassic true sharks underwent great diversification.<ref>{{Cite journal |last=Underwood |first=Charlie J. |date=March 2006 |title=Diversification of the Neoselachii (Chondrichthyes) during the Jurassic and Cretaceous |url=http://www.bioone.org/doi/abs/10.1666/04069.1 |journal=Paleobiology |language=en |volume=32 |issue=2 |pages=215–235 |doi=10.1666/04069.1 |bibcode=2006Pbio...32..215U |issn=0094-8373 |s2cid=86232401}}</ref> Sharks largely replaced the [[Hybodontiformes|hybodonts]], which had previously been a dominant group of shark-like fish during the Triassic and Early Jurassic.<ref name="Rees, J. A. N. 2008, p. 117–147">Rees, J. A. N., and Underwood, C. J., 2008, Hybodont sharks of the English Bathonian and Callovian (Middle Jurassic): Palaeontology, v. 51, no. 1, p. 117–147.</ref>