{{Short description|Extinct clade of therapsids}} {{Automatic taxobox | image = Iziko Diictodon Hibernating Pair.JPG | image_caption = Skeleton of ''Diictodon'' | image2 = Placerias.jpg | image2_caption = Skeleton of ''Placerias'' | fossil_range = <br /> Middle Permian (Wordian) to Late Triassic (late Norian or Rhaetian) {{fossil range|268|211|latest=205}} {{Period fossil range|Permian-Triassic|268|211|latest=205}} | display_parents = 2 | taxon = Dicynodontia | authority = Owen, 1859 | subdivision_ranks = Clades & genera | subdivision = See text | synonyms = Dicynodonta<ref>{{Cite journal |last=Lankester |first=E. Ray |date=1877-10-01 |title=Notes on the embryology and classification of the animal kingdom: Comprising a revision of speculations relative to the origin and significance of the germ-layers. |journal=Journal of Cell Science |volume=s2-17 |issue=68 |pages=399–454 |doi=10.1242/jcs.s2-17.68.399 |issn=0021-9533}}</ref> }}
'''Dicynodontia''' is an extinct clade of anomodonts, an extinct type of non-mammalian therapsid. Dicynodonts were herbivores that typically bore a pair of tusks, hence their name, which means 'two dog tooth'. Members of the group possessed a horny, typically toothless beak, unique amongst all synapsids. Dicynodonts first appeared in Southern Pangaea during the mid-Permian, ca. 270–260 million years ago, and became globally distributed and the dominant herbivorous animals in the Late Permian, ca. 260–252 Mya. They were devastated by the end-Permian mass extinction that wiped out most other therapsids ca. 252 Mya. They rebounded at beginning of the following Triassic, but subsequently declined during the Late Triassic and died out towards the end of that period. They were the most successful and diverse of the non-mammalian therapsids, with over 80–90 genera known, varying from rat-sized burrowers to elephant-sized megaherbivores.
==Characteristics== thumb|left|Dicynodont fossils [[Image:Diictodon-A72-03.jpg|thumb|right|''Diictodon'' life-sized model]] The dicynodont skull is highly specialised, light but strong, with the synapsid temporal openings at the rear of the skull greatly enlarged to accommodate larger jaw muscles. The front of the skull and the lower jaw are generally narrow and, in all but a number of primitive forms, toothless. Instead, the front of the mouth was equipped with a keratinous horny beak, as in turtles and ceratopsian dinosaurs. Food was processed by the retraction of the lower jaw when the mouth closed, producing a powerful shearing action,<ref name=Crompton>{{cite journal |last1=Crompton |first1=A. W. |last2=Hotton |first2=N. |year=1967 |title=Functional morphology of the masticatory apparatus of two dicynodonts (Reptilia, Therapsida) |journal=Postilla |volume=109 |pages=1–51}}</ref> which would have enabled dicynodonts to cope with tough plant material. Dicynodonts typically had a pair of enlarged maxillary caniniform teeth, analogous to the tusks present in some living mammals. In the earliest genera, they were merely enlarged teeth, but in later forms they independently evolved into ever-growing teeth like mammal tusks multiple times.<ref>{{Cite journal |last1=Whitney |first1=M. R. |last2=Angielczyk |first2=K. D. |last3=Peecook |first3=B. R. |last4=Sidor |first4=C. A. |year=2021 |title=The evolution of the synapsid tusk: Insights from dicynodont therapsid tusk histology |journal=Proceedings of the Royal Society B: Biological Sciences |volume=288 |issue=1961 |article-number=20211670 |doi=10.1098/rspb.2021.1670 |pmc=8548784 |pmid=34702071 |s2cid=239890042}}</ref> In some dicynodonts, the presence of tusks has been suggested to be sexually dimorphic.<ref>{{Cite journal |last1=Angielczyk |first1=Kenneth D. |last2=Benoit |first2=Julien |last3=Rubidge |first3=Bruce S. |date=February 2021 |editor-last=Ruta |editor-first=Marcello |title=A new tusked cistecephalid dicynodont (Therapsida, Anomodontia) from the upper Permian upper Madumabisa Mudstone Formation, Luangwa Basin, Zambia |url=https://onlinelibrary.wiley.com/doi/10.1002/spp2.1285 |journal=Papers in Palaeontology |language=en |volume=7 |issue=1 |pages=405–446 |doi=10.1002/spp2.1285 |bibcode=2021PPal....7..405A |s2cid=210304700 |issn=2056-2799|url-access=subscription }}</ref> Some dicynodonts such as ''Stahleckeria'' lacked true tusks and instead bore tusk-like extensions on the side of the beak.<ref>{{Cite journal |last1=Kammerer |first1=Christian F. |last2=Ordoñez |first2=Maria de los Angeles |date=2021-06-01 |title=Dicynodonts (Therapsida: Anomodontia) of South America |url=https://www.sciencedirect.com/science/article/pii/S0895981121000183 |journal=Journal of South American Earth Sciences |language=en |volume=108 |article-number=103171 |doi=10.1016/j.jsames.2021.103171 |bibcode=2021JSAES.10803171K |s2cid=233565963 |issn=0895-9811|url-access=subscription }}</ref><ref name=Colbert>Colbert, E. H., (1969), ''Evolution of the Vertebrates'', John Wiley & Sons Inc (2nd ed.)</ref>{{rp|139}} Like some other anomodonts, the skull roof shows the development of a novel skull bone, the "preparietal" that is not found in earlier synapsids nor in the cynodont ancestors of mammals. It is unpaired and forms the anterior (forward) margin of the pineal foramen. Similar bones, also called "preparietals" are found in gorgonopsid and biarmosuchian therapsids, though these are thought to have evolved convergently in each group.<ref>{{Cite journal |last1=Marilao |first1=Lianna M. |last2=Kulik |first2=Zoe T. |last3=Sidor |first3=Christian A. |date=2020-03-03 |title=Histology of the preparietal: a neomorphic cranial element in dicynodont therapsids |url=https://www.tandfonline.com/doi/full/10.1080/02724634.2020.1770775 |journal=Journal of Vertebrate Paleontology |language=en |volume=40 |issue=2 |article-number=e1770775 |doi=10.1080/02724634.2020.1770775 |bibcode=2020JVPal..40E0775M |issn=0272-4634|url-access=subscription }}</ref> Dicynodonts ancestrally had three vertebrae in the sacrum, though this rose to over 6 vertebrae in some dicynodonts as a result of both vertebrae duplication and incorporation of caudal vertebrae into the sacrum.<ref>{{Cite journal |last=Griffin |first=Christopher T. |last2=Angielczyk |first2=Kenneth D. |date=February 2019 |title=The evolution of the dicynodont sacrum: constraint and innovation in the synapsid axial column |url=https://www.cambridge.org/core/product/identifier/S0094837318000490/type/journal_article |journal=Paleobiology |language=en |volume=45 |issue=1 |pages=201–220 |doi=10.1017/pab.2018.49 |issn=0094-8373|url-access=subscription }}</ref>
Dicynodonts vary enormously in size. The smallest were rat-sized, a size common amongst Permian members of the group, while Triassic members of the group were typically much larger,<ref>{{Cite journal |last=King |first=Gillian M. |date=June 1993 |title=Species longevity and generic diversity in dicynodont mammal-like reptiles |url=https://linkinghub.elsevier.com/retrieve/pii/003101829390074S |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |language=en |volume=102 |issue=3–4 |pages=321–332 |doi=10.1016/0031-0182(93)90074-S |bibcode=1993PPP...102..321K |url-access=subscription }}</ref> with the youngest known member ''Lisowicia'' also being the largest known, around the size of an elephant, with a body mass estimated at {{Convert|5880|kg|lb}}.<ref>{{Cite journal |last1=Romano |first1=Marco |last2=Manucci |first2=Fabio |date=2021-04-03 |title=Resizing Lisowicia bojani: volumetric body mass estimate and 3D reconstruction of the giant Late Triassic dicynodont |url=https://www.tandfonline.com/doi/full/10.1080/08912963.2019.1631819 |journal=Historical Biology |language=en |volume=33 |issue=4 |pages=474–479 |doi=10.1080/08912963.2019.1631819 |bibcode=2021HBio...33..474R |issn=0891-2963|doi-access=free }}</ref> Many at least Triassic dicynodonts may have held their hindlimbs in a relatively erect posture while having more splayed forelimbs,<ref name=":0" /><ref>{{Cite journal |last=Ray |first=Sanghamitra |date=November 2006 |title=Functional and Evolutionary Aspects of the Postcranial Anatomy of Dicynodonts (Synapsida, Therapsida) |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1475-4983.2006.00597.x |journal=Palaeontology |language=en |volume=49 |issue=6 |pages=1263–1286 |doi=10.1111/j.1475-4983.2006.00597.x |bibcode=2006Palgy..49.1263R |issn=0031-0239}}</ref><ref>{{Cite journal |last1=Preuschoft |first1=Holger |last2=Krahl |first2=Anna |last3=Werneburg |first3=Ingmar |date=2022-10-05 |title=From sprawling to parasagittal locomotion in Therapsida: A preliminary study of historically collected museum specimens |url=https://vertebrate-zoology.arphahub.com/article/85989/ |journal=Vertebrate Zoology |volume=72 |pages=907–936 |doi=10.3897/vz.72.e85989 |doi-access=free |issn=2625-8498}}</ref> though ''Lisowicia'' likely to have had erect forelimbs as well.<ref name=":0" />
===Soft tissue anatomy=== Possible hair remnants in Permian carnivore coprolites have been suggested to have possibly been from dicynodonts, as digested dicynodont bones are abundant in the coprolites.<ref>{{cite journal | doi = 10.1111/let.12156 | title=Microbiota and food residues including possible evidence of pre-mammalian hair in Upper Permian coprolites from Russia | journal=Lethaia| volume=49 | issue=4 | pages=455–477 | year=2016 | last1=Bajdek | first1=Piotr | last2=Qvarnström | first2=Martin | last3=Owocki | first3=Krzysztof | last4=Sulej | first4=Tomasz | last5=Sennikov | first5=Andrey G. | last6=Golubev | first6=Valeriy K. | last7=Niedźwiedzki | first7=Grzegorz | bibcode=2016Letha..49..455B }}</ref> However specimens of ''Lystrosaurus'' fossilized with mummified skin have found that the skin surface was covered in numerous overlapping tubercules.<ref>{{Cite journal |last1=Smith |first1=Roger M.H. |last2=Botha |first2=Jennifer |last3=Viglietti |first3=Pia A. |date=October 2022 |title=Taphonomy of drought afflicted tetrapods in the Early Triassic Karoo Basin, South Africa |url=https://linkinghub.elsevier.com/retrieve/pii/S0031018222003777 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |language=en |volume=604 |article-number=111207 |doi=10.1016/j.palaeo.2022.111207|bibcode=2022PPP...60411207S |s2cid=251781291 |url-access=subscription }}</ref><ref>{{Cite journal |last1=Mooney |first1=Ethan D. |last2=Maho |first2=Tea |last3=Philp |first3=R. Paul |last4=Bevitt |first4=Joseph J. |last5=Reisz |first5=Robert R. |date=2024-01-22 |title=Paleozoic cave system preserves oldest-known evidence of amniote skin |url=https://www.cell.com/current-biology/abstract/S0960-9822(23)01663-9 |journal=Current Biology |language=English |volume=34 |issue=2 |pages=417–426.e4 |doi=10.1016/j.cub.2023.12.008 |issn=0960-9822 |pmid=38215745 |bibcode=2024CBio...34..417M |url-access=subscription }}</ref> ''Pentasauropus'' dicynodont tracks suggest that dicynodonts had fleshy pads on their feet.<ref>{{cite journal|title=Triassic pentadactyl tracks from the Los Menucos Group (Río Negro province, Patagonia Argentina): possible constraints on the autopodial posture of Gondwanan trackmakers|first1=Paolo|last1=Citton|first2=Ignacio|last2=Díaz-Martínez|first3=Silvina|last3=de Valais|first4=Carlos|last4=Cónsole-Gonella|date=7 August 2018|journal=PeerJ|volume=6|article-number=e5358|doi=10.7717/peerj.5358|pmid=30123702|pmc=6086091 |doi-access=free }}</ref>
=== Possible endothermy === Dicynodonts have long been suspected of being warm-blooded animals. Their bones are highly vascularised and possess Haversian canals, and their bodily proportions are conducive to heat preservation.<ref>{{cite journal |last1=Bakker |first1=Robert T. |title=Dinosaur renaissance |journal=Scientific American |date=April 1975 |volume=232 |issue=4 |pages=58–79 |doi=10.1038/scientificamerican0475-58|bibcode=1975SciAm.232d..58B }}</ref> In young specimens, the bones are so highly vascularised that they exhibit higher channel densities than most other therapsids.<ref>{{cite journal | last1 = Botha-Brink | first1 = Jennifer | last2 = Angielczyk | first2 = Kenneth D. | year = 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> Yet, studies on Late Triassic dicynodont coprolites paradoxically showcase digestive patterns more typical of animals with slow metabolisms.<ref>{{cite journal |last1=Bajdek |first1=Piotr |last2=Owocki |first2=Krzysztof |last3=Niedźwiedzki |first3=Grzegorz |title=Putative dicynodont coprolites from the Upper Triassic of Poland |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |date=2014 |volume=411 |pages=1–17 |doi=10.1016/j.palaeo.2014.06.013|bibcode=2014PPP...411....1B }}</ref> A 2017 study using chemical analysis suggested that cynodonts and dicynodonts both developed warm blood independently before the Permian extinction.<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 MH |last10=Steyer |first10=J. Sébastien |last11=Viglietti |first11=Pia A |last12=Wang |first12=Xu |last13=Lécuyer |first13=Christophe |title=Oxygen isotopes suggest elevated thermometabolism within multiple Permo-Triassic therapsid clades |journal=eLife |date=2017 |volume=6 |article-number=e28589 |doi=10.7554/eLife.28589|pmid=28716184 |pmc=5515572 |doi-access=free }}</ref>
=== Reproduction and social behavour === [[File:Lystrosaurus_embryo.png|thumb|Preserved embryo of dicynodont ''Lystrosaurus'' from the Early Triassic of South Africa, with life restoration showing embryo curled up in inferred (but unpreserved) egg]] A preserved tightly curled embryonic individual of ''Lystrosaurus'' from the Early Triassic of South Africa suggests that dicynodonts laid eggs, as is thought to be ancestral for synapsids and amniotes, though the lack of preserved eggshell suggests that the eggs were probably soft and leathery like in living monotreme mammals, and as is suggested to be ancestral for amniotes. The relatively large size of the eggs suggests individuals of ''Lystrosaurus'' were precocial (relatively independent from birth), and the egg had large yolk reserves for development, indicating that dicynodonts did not produce milk like mammals (the eggs of milk-producing monotremes are relatively small compared to body size) and perhaps at least some non-mammalian cynodonts.<ref>{{Cite journal |last1=Benoit |first1=Julien |last2=Fernandez |first2=Vincent |last3=Botha |first3=Jennifer |date=2026-04-09 |editor-last=Fröbisch |editor-first=Jörg |title=The first non-mammalian synapsid embryo from the Triassic of South Africa |journal=PLOS ONE |language=en |volume=21 |issue=4 |article-number=e0345016 |doi=10.1371/journal.pone.0345016 |doi-access=free |pmid=41955224 |pmc=13065020 |bibcode=2026PLoSO..2145016B |issn=1932-6203}}</ref>
Fossil communal latrines,<ref>{{Cite journal |last=Fiorelli |first=Lucas E. |last2=Ezcurra |first2=Martín D. |last3=Hechenleitner |first3=E. Martín |last4=Argañaraz |first4=Eloisa |last5=Taborda |first5=Jeremías R. A. |last6=Trotteyn |first6=M. Jimena |last7=von Baczko |first7=M. Belén |last8=Desojo |first8=Julia B. |date=2013-11-28 |title=The oldest known communal latrines provide evidence of gregarism in Triassic megaherbivores |url=https://www.nature.com/articles/srep03348 |journal=Scientific Reports |language=en |volume=3 |issue=1 |doi=10.1038/srep03348 |issn=2045-2322 |pmc=3842779 |pmid=24287957}}</ref> preserved trackways showing adults and juvenile dicynodonts walking alongside each other, as well as large fossil aggregations of both adult and juvenile dicynodonts, suggests that at least some dicynodonts engaged in post-hatching parental care and were gregarious.<ref>{{Cite journal |last=Bolton |first=Andrew D. |last2=Mangera |first2=Taahirah |last3=Benoit |first3=Julien |date=2025-08-12 |title=150 years of synapsid paleoneurology: the origins of the mammalian brain, behavior, sense organs and physiology |url=https://www.cambridge.org/core/product/identifier/S0022336025101212/type/journal_article |journal=Journal of Paleontology |language=en |pages=1–29 |doi=10.1017/jpa.2025.10121 |issn=0022-3360|doi-access=free }}</ref>
== History of discovery and research == [[Image:Dicynodon lacerticeps.jpg|thumb|right|''Dicynodon lacerticeps'' skull illustration, first published in an 1845 description by Sir Richard Owen]] A 2024 paper posited that rock art of a superficially walrus-like imaginary creature with downcurved tusks created by the San people of South Africa prior to 1835 may have been partly inspired by fossil dicynodont skulls which erode out of rocks in the area.<ref>{{cite journal |last=Benoit |first=J |year=2024 |title=A possible later stone age painting of a dicynodont (Synapsida) from the South African Karoo |journal=PLOS ONE |volume=19 |issue=9 |article-number=e0309908 |doi=10.1371/journal.pone.0309908 |doi-access=free |pmid=39292694 |pmc=11410247 }}</ref>
Dicynodonts have been known to science since the mid-1800s. The South African geologist Andrew Geddes Bain gave the first description of dicynodonts in 1845. At the time, Bain was a supervisor for the construction of military roads under the Corps of Royal Engineers and had found many reptilian fossils during his surveys of South Africa. Bain described these fossils in an 1845 letter published in ''Transactions of the Geological Society of London'', calling them "bidentals" for their two prominent tusks.<ref name="BAG45">{{cite journal |last=Bain |first=A.G. |year=1845 |title=On the discovery of fossil remains of bidental and other reptiles in South Africa |journal=Transactions of the Geological Society of London |volume=1 |pages=53–59 |doi=10.1144/GSL.JGS.1845.001.01.72|bibcode=1845QJGS....1..317B |hdl=2027/uc1.c034667778 |s2cid=128602890 |url=https://zenodo.org/record/1673362 }}</ref> In that same year, the English paleontologist Richard Owen named two species of dicynodonts from South Africa: ''Dicynodon lacerticeps'' and ''Dicynodon bainii''. Since Bain was preoccupied with the Corps of Royal Engineers, he wanted Owen to describe his fossils more extensively. Owen did not publish a description until 1876 in his ''Descriptive and Illustrated Catalogue of the Fossil Reptilia of South Africa in the Collection of the British Museum''.<ref name="OR76">{{cite book |last=Owen |first=R. |year=1876 |title=Descriptive and Illustrated Catalogue of the Fossil Reptilia of South Africa in the Collection of the British Museum |publisher=British Museum |location=London |page=88}}</ref> By this time, many more dicynodonts had been described. In 1859, another important species called ''Ptychognathus declivis'' was named from South Africa. In the same year, Owen named the group Dicynodontia.<ref name="OR60">{{cite journal |last=Owen |first=R. |year=1860 |title=On the orders of fossil and recent Reptilia, and their distribution in time |journal=Report of the Twenty-Ninth Meeting of the British Association for the Advancement of Science |volume=1859 |pages=153–166}}</ref> In his ''Descriptive and Illustrated Catalogue'', Owen honored Bain by erecting Bidentalia as a replacement name for his Dicynodontia.<ref name="OR76" /> The name Bidentalia quickly fell out of use in the following years, replaced by popularity of Owen's Dicynodontia.<ref name="KA09">{{cite journal |last=Kammerer |first=C.F. |author2=Angielczyk, K.D. |year=2009 |title=A proposed higher taxonomy of anomodont therapsids |journal=Zootaxa |volume=2018 |pages=1–24 |doi=10.11646/zootaxa.2018.1.1 |bibcode=2009Zoot.20188.1.1K |url=http://www.mapress.com/zootaxa/2009/f/z02018p024f.pdf}}</ref>
==Evolutionary history== [[File:Eodicynodon oosthuizeni.png|thumb|''Eodicynodon'', a basal dicynodont from middle Permian South Africa.]] {{Multiple image | direction = vertical | image1 = Lisowicia bojani Wikipedia Juandertal.jpg | image2 = Lisowicia Size Comparison.svg | footer = ''Lisowicia'', from Late Triassic Poland }} Dicynodonts first appeared during the Middle Permian in the Southern Hemisphere, with South Africa being the centre of their known diversity, and underwent a rapid evolutionary radiation, becoming globally distributed and amongst the most successful and abundant land vertebrates during the Late Permian.<ref>{{Cite journal|last=Kurkin|first=A. A.|date=July 2011|title=Permian anomodonts: Paleobiogeography and distribution of the group|url=http://link.springer.com/10.1134/S0031030111030075|journal=Paleontological Journal|language=en|volume=45|issue=4|pages=432–444|doi=10.1134/S0031030111030075|bibcode=2011PalJ...45..432K |s2cid=129331000|issn=0031-0301|url-access=subscription}}</ref><ref>{{Cite journal|last1=Olroyd|first1=Savannah L.|last2=Sidor|first2=Christian A.|date=August 2017|title=A review of the Guadalupian (middle Permian) global tetrapod fossil record|journal=Earth-Science Reviews|volume=171|pages=583–597|doi=10.1016/j.earscirev.2017.07.001|bibcode=2017ESRv..171..583O|issn=0012-8252|doi-access=free}}</ref> During this time, they included a large variety of ecotypes, including large, medium-sized, and small herbivores and short-limbed mole-like burrowers.<ref>{{cite book|doi=10.1515/9783110341553-005|chapter=5. Non-Mammalian synapsids: The deep roots of the mammalian family tree |title=Mammalian Evolution, Diversity and Systematics |year=2018 |last1=Angielczyk |first1=Kenneth D. |last2=Kammerer |first2=Christian F. |pages=117–198 |isbn=978-3-11-034155-3 |s2cid=92370138 }}</ref>
Only four lineages are known to have survived the Great Dying; the first three represented with a single genus each: ''Myosaurus'', ''Kombuisia'', and ''Lystrosaurus'', the latter being the most common and widespread herbivores of the Induan (earliest Triassic). None of these survived long into the Triassic. The fourth group was the Kannemeyeriiformes, the only dicynodonts who diversified during the Triassic.<ref>{{cite journal|title=On the validity and phylogenetic position of ''Eubrachiosaurus browni'', a kannemeyeriiform dicynodont (Anomodontia) from Triassic North America |first1=Christian F.|last1=Kammerer|first2=Jörg|last2=Fröbisch|first3=Kenneth D.|last3=Angielczyk|date=31 May 2013|journal=PLOS ONE |volume=8 |issue=5 |article-number=e64203 |doi=10.1371/journal.pone.0064203|pmid=23741307|pmc=3669350|bibcode=2013PLoSO...864203K|doi-access=free}}</ref> These stocky, pig- to ox-sized animals were successful herbivores worldwide for much of the Triassic period. However during the late Triassic during the Norian and possibly the Carnian, they declined, though the nature and timing of this decline is not well agreed upon. Suggested influencing factors include the Carnian pluvial episode.<ref>{{Cite journal |last1=Racki |first1=Grzegorz |last2=Lucas |first2=Spencer G. |date=2020-04-20 |title=Timing of dicynodont extinction in light of an unusual Late Triassic Polish fauna and Cuvier's approach to extinction |url=https://www.tandfonline.com/doi/full/10.1080/08912963.2018.1499734 |journal=Historical Biology |language=en |volume=32 |issue=4 |pages=452–461 |doi=10.1080/08912963.2018.1499734 |bibcode=2020HBio...32..452R |issn=0891-2963|url-access=subscription }}</ref> Fossils of an Asian elephant-sized dicynodont ''Lisowicia bojani'' discovered in Poland indicate that dicynodonts survived at least until the late Norian or earliest Rhaetian (latest Triassic, at earliest 211 million years ago,<ref>{{Cite journal |last1=Kowal-Linka |first1=Monika |last2=Krzemińska |first2=Ewa |last3=Czupyt |first3=Zbigniew |date=January 2019 |title=The youngest detrital zircons from the Upper Triassic Lipie Śląskie (Lisowice) continental deposits (Poland): Implications for the maximum depositional age of the Lisowice bone-bearing horizon |url=https://linkinghub.elsevier.com/retrieve/pii/S0031018218307545 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |language=en |volume=514 |pages=487–501 |doi=10.1016/j.palaeo.2018.11.012|bibcode=2019PPP...514..487K |url-access=subscription }}</ref> and probably no later than around 205 million years ago<ref>{{Cite journal |last1=Mujal |first1=Eudald |last2=Sues |first2=Hans-Dieter |last3=Moreno |first3=Raphael |last4=Schaeffer |first4=Joep |last5=Sobral |first5=Gabriela |last6=Chakravorti |first6=Sanjukta |last7=Spiekman |first7=Stephan N.F. |last8=Schoch |first8=Rainer R. |date=May 2025 |title=Triassic terrestrial tetrapod faunas of the Central European Basin, their stratigraphical distribution, and their palaeoenvironments |journal=Earth-Science Reviews |language=en |volume=264 |article-number=105085 |doi=10.1016/j.earscirev.2025.105085|doi-access=free |bibcode=2025ESRv..26405085M }}</ref>); this animal was also the largest known dicynodont species.<ref name=":0">{{cite journal |author1=Tomasz Sulej |author2=Grzegorz Niedźwiedzki |year=2019 |title=An elephant-sized Late Triassic synapsid with erect limbs |journal=Science |volume=363 |issue= 6422|pages= 78–80|doi=10.1126/science.aal4853 |pmid=30467179 |bibcode=2019Sci...363...78S |doi-access=free |url=https://zenodo.org/record/2532919 }}</ref><ref name="NYT-20190104">{{cite news |last=St. Fleur |first=Nicholas |title=An Elephant-Size Relative of Mammals That Grazed Alongside Dinosaurs |url=https://www.nytimes.com/2019/01/04/science/dicynodonts-fossils-poland.html |date=4 January 2019 |work=The New York Times |access-date=6 January 2019 }}</ref>
Six fragments of fossil bone discovered in Queensland, Australia, were interpreted as remains of a skull in 2003. This suggested by some author to indicate that dicynodonts survived into the Cretaceous in southern Gondwana.<ref name="Thulborn">{{cite journal |last1=Thulborn |first1=T. |last2=Turner |first2=S. |title=The last dicynodont: an Australian Cretaceous relict|journal=Proceedings of the Royal Society B: Biological Sciences|volume=270|issue=1518|year=2003|pages=985–993|doi=10.1098/rspb.2002.2296 |jstor=3558635 |pmid=12803915 |pmc=1691326 |bibcode=2003PBioS.270..985T }}</ref> The dicynodont affinity of these specimens was questioned (including a proposal that they belonged to a baurusuchian crocodyliform by Agnolin et al. in 2010),<ref name="agnolinetal2010">{{cite journal |last=Agnolin |first=F. L. |author2=Ezcurra, M. D. |author3=Pais, D. F. |author4= Salisbury, S. W. |year=2010 |title=A reappraisal of the Cretaceous non-avian dinosaur faunas from Australia and New Zealand: Evidence for their Gondwanan affinities |journal=Journal of Systematic Palaeontology |volume=8 |issue=2 |pages=257–300 |doi=10.1080/14772011003594870|bibcode=2010JSPal...8..257A |s2cid=130568551 |url=https://espace.library.uq.edu.au/view/UQ:206067/UQ206067.pdf }}</ref> and in 2019 Knutsen and Oerlemans considered this fossil to be of Plio-Pleistocene age, and reinterpreted it as a fossil of a large mammal, probably a diprotodontid marsupial.<ref>{{cite journal |author1=Espen M. Knutsen |author2=Emma Oerlemans |year=2019 |title=The last dicynodont? Re-assessing the taxonomic and temporal relationships of a contentious Australian fossil |journal=Gondwana Research |volume=77 |pages= 184–203|doi=10.1016/j.gr.2019.07.011 |s2cid=202908716 |doi-access= }}</ref>
With the decline and extinction of the kannemeyerids, there were to be no more dominant large synapsid herbivores until the middle Paleocene epoch (60 Ma) when mammals, distant descendants of cynodonts, began to diversify after the extinction of the non-avian dinosaurs.
==Systematics==
===Taxonomy=== Dicynodontia was originally named by the English paleontologist Richard Owen. It was erected as a family of the order Anomodontia and included the genera ''Dicynodon'' and ''Ptychognathus''. Other groups of Anomodontia included Gnathodontia, which included ''Rhynchosaurus'' (now known to be an archosauromorph) and Cryptodontia, which included ''Oudenodon''. Cryptodonts were distinguished from dicynodonts from their absence of tusks. Although it lacks tusks, ''Oudenodon'' is now classified as a dicynodont, and the name Cryptodontia is no longer used. Thomas Henry Huxley revised Owen's Dicynodontia as an order that included ''Dicynodon'' and ''Oudenodon''.<ref name=OHF04>{{cite journal |last=Osborn |first=H.F. |year=1904 |title=Reclassification of the Reptilia |journal=The American Naturalist |volume=38 |issue=446 |pages=93–115 |url=https://books.google.com/books?id=EHMWAAAAYAAJ |doi=10.1086/278383|bibcode=1904ANat...38...93O |s2cid=84492986 |url-access=subscription }}</ref> Dicynodontia was later ranked as a suborder or infraorder with the larger group Anomodontia, which is classified as an order. The ranking of Dicynodontia has varied in recent studies, with Ivakhnenko (2008) considering it a suborder, Ivanchnenko (2008) considering it an infraorder, and Kurkin (2010) considering it an order.<ref name=KAA10>{{cite journal |last=Kurkin |first=A.A. |year=2010 |title=Late Permian dicynodonts of Eastern Europe |journal=Paleontological Journal |volume=44 |issue=6 |pages=72–80 |doi=10.1134/S0031030110060092|bibcode=2010PalJ...44..672K |s2cid=131459807 }}</ref>
Many higher taxa, including infraorders and families, have been erected as a means of classifying the large number of dicynodont species. Cluver and King (1983) recognised several main groups within Dicynodontia, including Eodicynodontidae (containing only ''Eodicynodon''), Endothiodontia, Pristerodontia (Pristerodontidae, Cryptodontidae, Geikiidae, Dicynodontidae, Lystrosauridae, and Kannemeyeriidae), Kingoriamorpha (containing only Kingoriidae), Diictodontia (Pylaecephalidae, Robertiidae, Cistecephalidae, Emydopidae, and Myosauridae), and Venyukoviamorpha.<ref name=CK83>{{cite journal |last=Cluver |first=M.A. |author2=King, G.M. |year=1983 |title=A reassessment of the relationships of Permian Dicynodontia (Reptilia, Therapsida) and a new classification of dicynodont |journal=Annals of the South African Museum |volume=91 |pages=195–273}}</ref> Most of these taxa are no longer considered valid. Kammerer and Angielczyk (2009) suggested that the problematic taxonomy and nomenclature of Dicynodontia and other groups results from the large number of conflicting studies and the tendency for invalid names to be mistakenly established.<ref name=KA09/>
{{Multiple image | total_width = 330 | image1 = Endothiodon.jpg | image2 = Endothiodon Scale V3.svg | footer = ''Endothiodon'' }}
{{Multiple image | total_width = 330 | image1 = Diictodon EF.jpg | image2 = Diictodon feliceps scale.svg | footer = ''Diictodon'' }}
[[File:Cistecephalus1DB.jpg|thumb|''Cistecephalus'']] [[Image:KingoriaDB.jpg|219x219px|thumb|''Dicynodontoides'', a small dicynodont from Africa's Upper Permian]][[Image:Myosaurus.jpg|thumb|220x220px|''Myosaurus'']][[File:Australobarbarus1DB.jpg|thumb|''Australobarbarus'']][[File:Aulacocephalodon12DB.jpg|thumb|''Aulacephalodon'']][[File:Geikia sppDB24.jpg|thumb|''Geikia'' (''G. elginensis and G. locusticeps'')]][[File:PelanomodonDB16.jpg|thumb|''Pelanomodon'']] [[File:Gordonia traquairi restoration and skull (cropped).jpg|thumb|''Gordonia'']]{{Multiple image | image1 = Lystrosaurus BW.jpg | image2 = Lystrosaurus_murrayi_updated.svg | footer = ''Lystrosaurus murrayi'' | total_width = | direction = vertical }}
[[File:Dinodontosaurus1DB.jpg|thumb|''Dinodontosaurus'']]{{Multiple image | total_width = 330 | image1 = Wadiasaurus1DB.jpg | image2 = Wadiasaurus indicus scale.svg | footer = ''Wadiasaurus'' }}
[[File:Woznikella.jpg|thumb|''Woznikella'']][[Image:Moghreberia.jpg|thumb|137x137px|''Moghreberia'']]{{Multiple image | total_width = 330 | image1 = Stahleckeria1DB.jpg | image2 = Stahleckeria potens scale.svg | footer = ''Stahleckeria'' }}
{{Multiple image | total_width = 330 | image1 = Ufudocyclops profile 2.png | image2 = Ufudocyclops scale.svg | footer = ''Ufudocyclops'' }}
=== Phylogeny === Below is a cladogram modified from Angielczyk et al. (2021):<ref name="Angielczyk2021">{{Cite journal|last1=Angielczyk |first1=K. D. |last2=Liu |first2=J. |last3=Yang |first3=W. |year=2021 |title=A Redescription of ''Kunpania scopulusa'', a Bidentalian Dicynodont (Therapsida, Anomodontia) from the ?Guadalupian of Northwestern China |journal=Journal of Vertebrate Paleontology |volume=41 |issue=1 |article-number=e1922428 |doi=10.1080/02724634.2021.1922428 |bibcode=2021JVPal..41E2428A |s2cid=236406006 }}</ref> {{clade |label1='''Dicynodontia''' |1={{clade |1=''Nyaphulia'' |2={{clade |1=''Eodicynodon'' |2={{clade |1=''Colobodectes'' |2={{clade |1=''Lanthanostegus'' |2={{clade |1=Pylaecephalidae |2={{clade |1=Eumantellidae |2={{clade |1=''Brachyprosopus'' |2={{clade |1=Endothiodontia |label2=Therochelonia |2={{clade |1=Emydopoidea |2=Bidentalia }} }} }} }} }} }} }} }} }} }}
=== Current classification === *'''Dicynodontia''' **''Brachyprosopus'' **''Colobodectes'' **''Eodicynodon'' **''Lanthanostegus'' **''Nyaphulia'' **Endothiodontia ***''Abajudon'' ***''Endothiodon'' ***''Niassodon'' **Eumantellidae ***''Pristerodon'' **Pylaecephalidae ***''Diictodon'' ***''Eosimops'' ***''Prosictodon'' ***''Robertia'' **Therochelonia ***Emydopoidea ****''Digalodon'' ****''Rastodon'' ****Cistecephalidae *****''Cistecephalus'' *****''Cistecephaloides'' *****''Kawingasaurus'' *****''Kembawacela'' *****''Sauroscaptor'' ****Emydopidae *****''Compsodon'' *****''Emydops'' ****Kingoriidae *****''Dicynodontoides'' *****''Kombuisia'' *****''Thliptosaurus'' ****Myosauridae *****''Myosauroides'' *****''Myosaurus'' ***Bidentalia ****''Kunpania'' ****Cryptodontia ***** ''Daqingshanodon'' ***** ''Keyseria'' *****Rhachiocephalidae ****** ''Kitchinganomodon'' ****** ''Rhachiocephalus'' *****Oudenodontidae ****** ''Australobarbarus'' ****** ''Oudenodon'' ****** ''Tropidostoma'' *****Geikiidae ****** ''Bulbasaurus'' ****** ?''Idelesaurus'' ****** ?''Odontocyclops'' ****** Geikiinae ******* ''Aulacephalodon'' ******* ''Geikia'' ******* ''Pelanomodon'' ****Dicynodontoidea *****''Counillonia'' *****''Daptocephalus'' *****''Delectosaurus'' *****''Dicynodon'' *****''Dinanomodon'' ***** ''Elph'' *****''Gordonia'' *****''Interpresosaurus'' *****''Katumbia'' *****''Peramodon'' *****''Taoheodon'' *****''Turfanodon'' *****''Vivaxosaurus'' *****Lystrosauridae ******?''Basilodon'' ******?''Jimusaria'' ******?''Sintocephalus'' ******?''Syops'' ******''Euptychognathus'' ******''Kwazulusaurus'' ******''Lystrosaurus'' *****Kannemeyeriiformes ******''Angonisaurus'' ******Dinodontosauridae *******''Dinodontosaurus'' ******Shansiodontidae *******''Rhinodicynodon'' *******''Shansiodon'' *******''Tetragonias'' *******''Vinceria'' ******Kannemeyeriidae *******''Acratophorus'' *******''Dolichuranus'' *******''Kannemeyeria'' *******''Parakannemeyeria'' *******''Rabidosaurus'' *******''Rechnisaurus'' *******''Rhadiodromus'' *******''Shaanbeikannemeyeria'' *******''Sinokannemeyeria'' *******''Uralokannemeyeria'' *******''Wadiasaurus'' *******''Xiyukannemeyeria'' ******Stahleckeriidae *******?''Sungeodon'' *******''Woznikella'' ******* Placeriinae ******** ''Argodicynodon'' ******** ''Lisowicia'' ******** ''Moghreberia'' ******** ''Placerias'' ******** ''Pentasaurus'' ******** ''Zambiasaurus'' *******Stahleckeriinae ******** ''Eubrachiosaurus'' ******** ''Ischigualastia'' ******** ''Jachaleria'' ******** ''Sangusaurus'' ******** ''Stahleckeria'' ******** ''Ufudocyclops''
==See also== * Dromasauria * Evolution of mammals
==References== {{Reflist}}
==Further reading== * Carroll, R. L. (1988), ''Vertebrate Paleontology and Evolution'', WH Freeman & Co. * Cox, B., Savage, R.J.G., Gardiner, B., Harrison, C. and Palmer, D. (1988) ''The Marshall illustrated encyclopedia of dinosaurs & prehistoric animals'', 2nd Edition, Marshall Publishing * King, Gillian M., "Anomodontia" Part 17 C, ''Encyclopedia of Paleoherpetology'', Gutsav Fischer Verlag, Stuttgart and New York, 1988 * King, Gillian M., 1990, ''The Dicynodonts: A Study in Palaeobiology'', Chapman and Hall, London and New York
==External links== *[https://web.archive.org/web/20060222040556/http://www.palaeos.com/Vertebrates/Units/400Therapsida/400.725.html Therapsida : Neotherapsida : Dicynodontia] - Palaeos
{{Anomodontia|D.}} {{Taxonbar|from=Q131682}}
Category:Dicynodontia Category:Guadalupian first appearances Category:Late Triassic extinctions Category:Taxa named by Richard Owen