Editing Permian–Triassic extinction event (section)

====Synapsids====
[[File:Lystrosaurus hedini.JPG|thumb|upright=1.25|right|''[[Lystrosaurus]]'' was by far the most abundant early Triassic land vertebrate.]]
''[[Lystrosaurus]]'', a pig-sized herbivorous [[dicynodont]] [[therapsid]], constituted as much as 90% of some earliest Triassic land vertebrate fauna, although some recent evidence has called into question its status as a post-PTME [[disaster taxon]].<ref>{{cite journal |last1=Modesto |first1=Sean P. |date=16 December 2020 |title=The Disaster Taxon Lystrosaurus: A Paleontological Myth |journal=[[Frontiers in Earth Science]] |volume=8 |page=617 |doi=10.3389/feart.2020.610463 |bibcode=2020FrEaS...8..617M |doi-access=free }}</ref> The dicynodont genus is often used as a biostratigraphic marker for the PTME.<ref>{{Cite journal |last1=Angielczyk |first1=Kenneth D. |last2=Liu |first2=Jun |last3=Sidor |first3=Christian A. |last4=Yang |first4=Wan |date=November 2022 |title=The stratigraphic and geographic occurrences of Permo-Triassic tetrapods in the Bogda Mountains, NW China — Implications of a new cyclostratigraphic framework and Bayesian age model |journal=[[Journal of African Earth Sciences]] |language=en |volume=195 |pages=104655 |doi=10.1016/j.jafrearsci.2022.104655 |doi-access=free }}</ref> The evolutionary success of ''Lystrosaurus'' in the aftermath of the PTME is believed to be attributable to the dicynodont taxon's grouping behaviour and tolerance for extreme and highly variable climatic conditions.<ref>{{cite journal |last1=Viglietti |first1=Pia A. |last2=Smith |first2=Roger M. H. |last3=Compton |first3=John S. |date=15 December 2013 |title=Origin and palaeoenvironmental significance of Lystrosaurus bonebeds in the earliest Triassic Karoo Basin, South Africa |url=https://www.sciencedirect.com/science/article/abs/pii/S0031018213003787 |journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]] |volume=392 |pages=9–21 |doi=10.1016/j.palaeo.2013.08.015 |bibcode=2013PPP...392....9V |access-date=31 May 2023}}</ref> Other likely factors behind the success of ''Lystrosaurus'' included extremely fast growth rate exhibited by the dicynodont genus,<ref>{{cite journal |last1=Botha-Brink |first1=Jennifer |last2=Angielczyk |first2=Kenneth D. |date=26 July 2010 |title=Do extraordinarily high growth rates in Permo-Triassic dicynodonts (Therapsida, Anomodontia) explain their success before and after the end-Permian extinction? |journal=[[Zoological Journal of the Linnean Society]] |volume=160 |issue=2 |pages=341–365 |doi=10.1111/j.1096-3642.2009.00601.x |doi-access=free }}</ref> along with its early onset of sexual maturity.<ref name="BreedingYoung">{{cite journal |last1=Botha-Brink |first1=Jennifer |last2=Codron |first2=Daryl |last3=Huttenlocker |first3=Adam K. |last4=Angielczyk |first4=Kenneth D. |last5=Ruta |first5=Marcello |date=5 April 2016 |title=Breeding Young as a Survival Strategy during Earth's Greatest Mass Extinction |journal=[[Scientific Reports]] |volume=6 |issue=1 |page=24053 |doi=10.1038/srep24053 |pmid=27044713 |pmc=4820772 |bibcode=2016NatSR...624053B }}</ref> Antarctica may have served as a refuge for dicynodonts during the PTME from which surviving dicynodonts spread out of in its aftermath.<ref name="AntarcticRefuge">{{cite journal |last1=Fröbisch |first1=Jörg |last2=Angielczyk |first2=Kenneth D. |last3=Sidor |first3=Christian A. |date=3 December 2009 |title=The Triassic dicynodont Kombuisia (Synapsida, Anomodontia) from Antarctica, a refuge from the terrestrial Permian-Triassic mass extinction |url=https://link.springer.com/article/10.1007/s00114-009-0626-6 |journal=[[Naturwissenschaften]] |volume=97 |issue=2 |pages=187–196 |doi=10.1007/s00114-009-0626-6 |pmid=19956920 |s2cid=20557454 |access-date=31 May 2023}}</ref> Ichnological evidence from the earliest Triassic of the Karoo Basin shows dicynodonts were abundant in the immediate aftermath of the biotic crisis.<ref>{{cite journal |last1=Marchetti |first1=Lorenzo |last2=Klein |first2=Hendrik |last3=Buchwitz |first3=Michael |last4=Ronchi |first4=Ausonio |last5=Smith |first5=Roger M. H. |last6=De Klerk |first6=William J. |last7=Sciscio |first7=Lara |last8=Groenewald |first8=Gideon H. |date=August 2019 |title=Permian-Triassic vertebrate footprints from South Africa: Ichnotaxonomy, producers and biostratigraphy through two major faunal crises |journal=[[Gondwana Research]] |volume=72 |pages=139–168 |doi=10.1016/j.gr.2019.03.009 |bibcode=2019GondR..72..139M |s2cid=133781923 |doi-access=free }}</ref> Smaller carnivorous [[cynodont]] [[therapsids]] also survived, a group that included the ancestors of mammals.<ref name="BodySizeReductions" /> As with dicynodonts, selective pressures favoured endothermic [[Epicynodontia|epicynodonts]].<ref>{{cite journal |last1=Rey |first1=Kévin |last2=Amiot |first2=Romain |last3=Fourel |first3=François |last4=Abdala |first4=Fernando |last5=Fluteau |first5=Frédéric |last6=Jalil |first6=Nour-Eddine |last7=Liu |first7=Jun |last8=Rubidge |first8=Bruce S. |last9=Smith |first9=Roger M. H. |last10=Steyer |first10=J. Sébastien |last11=Viglietti |first11=Pia A. |last12=Wang |first12=Xu |last13=Lécuyer |first13=Christophe |date=18 July 2017 |title=Oxygen isotopes suggest elevated thermometabolism within multiple Permo-Triassic therapsid clades |journal=[[eLife]] |volume=6 |pages=e28589 |doi=10.7554/eLife.28589 |pmid=28716184 |pmc=5515572 |doi-access=free }}</ref> [[Therocephalia]]ns likewise survived; burrowing may have been a key adaptation that helped them make it through the PTME.<ref>{{cite journal |last1=Fontanarrosa |first1=Gabriela |last2=Abdala |first2=Fernando |last3=Kümmell |first3=Susanna |last4=Gess |first4=Robert |date=26 March 2019 |title=The manus of Tetracynodon (Therapsida: Therocephalia) provides evidence for survival strategies following the Permo-Triassic extinction |url=https://www.tandfonline.com/doi/abs/10.1080/02724634.2018.1491404 |journal=[[Journal of Vertebrate Paleontology]] |volume=38 |issue=4 |pages=(1)-(13) |doi=10.1080/02724634.2018.1491404 |hdl=11336/91246 |s2cid=109228166 |access-date=31 May 2023|hdl-access=free }}</ref> In the [[Karoo]] region of southern [[Africa]], the [[therocephalia]]ns ''[[Tetracynodon]]'', ''[[Moschorhinus]]'' and ''[[Ictidosuchoides]]'' survived, but do not appear to have been abundant in the Triassic.<ref name="BothaSmith2007LystrosaurusSpeciesComposition">{{cite journal |author1=Botha, J. |author2=Smith, R.M.H. |name-list-style=amp | year=2007 | title=Lystrosaurus species composition across the Permo–Triassic boundary in the Karoo Basin of South Africa | journal=[[Lethaia]] | volume=40 | pages=125–137 |url=http://www.nasmus.co.za/PALAEO/jbotha/pdfs/Botha%20and%20Smith%202007.pdf |archive-url=https://web.archive.org/web/20080910214110/http://www.nasmus.co.za/PALAEO/jbotha/pdfs/Botha%20and%20Smith%202007.pdf |url-status=dead |archive-date=2008-09-10 | access-date=2008-07-02 | doi=10.1111/j.1502-3931.2007.00011.x | issue=2 |bibcode=2007Letha..40..125B }}</ref> Early Triassic therocephalians were mostly survivors of the PTME rather than newly evolved taxa that originated during the evolutionary radiation in its aftermath.<ref>{{cite journal |last1=Huttenlocker |first1=Adam K. |last2=Sidor |first2=Christian A. |last3=Smith |first3=Roger M. H. |date=21 March 2011 |title=A new specimen of Promoschorhynchus (Therapsida: Therocephalia: Akidnognathidae) from the Lower Triassic of South Africa and its implications for theriodont survivorship across the Permo-Triassic boundary |url=https://www.tandfonline.com/doi/abs/10.1080/02724634.2011.546720 |journal=[[Journal of Vertebrate Paleontology]] |volume=31 |issue=2 |pages=405–421 |doi=10.1080/02724634.2011.546720 |bibcode=2011JVPal..31..405H |s2cid=129242450 |access-date=31 May 2023}}</ref> Both therocephalians and cynodonts, known collectively as [[Eutheriodontia|eutheriodonts]], decreased in body size from the Late Permian to the Early Triassic.<ref name="BodySizeReductions">{{cite journal |last1=Huttenlocker |first1=Adam K. |date=3 February 2014 |title=Body Size Reductions in Nonmammalian Eutheriodont Therapsids (Synapsida) during the End-Permian Mass Extinction |journal=[[PLOS ONE]] |volume=9 |issue=2 |pages=e87553 |doi=10.1371/journal.pone.0087553 |pmid=24498335 |pmc=3911975 |bibcode=2014PLoSO...987553H |doi-access=free }}</ref> This decrease in body size has been interpreted as an example of the Lilliput effect.<ref>{{cite journal |last1=Huttenlocker |first1=Adam K. |last2=Botha-Brink |first2=Jennifer |date=8 April 2014 |title=Bone microstructure and the evolution of growth patterns in Permo-Triassic therocephalians (Amniota, Therapsida) of South Africa |journal=[[PeerJ]] |volume=2 |pages=e325 |doi=10.7717/peerj.325 |pmid=24765566 |pmc=3994631 |doi-access=free }}</ref>