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Line 11: }} '''Docodonta''' is an [[Order (biology)|order]] of extinct [[Mesozoic]] [[Mammaliaformes|mammaliaforms]] (advanced [[cynodont]]s closely related to true [[Crown group|crown-group]] [[mammal]]s). They were among the most common mammaliaforms of their time, persisting from the [[Middle Jurassic]] to the [[Early Cretaceous]] across the continent of [[Laurasia]] (modern-day [[North America]], [[Europe]], and [[Asia]]). They are distinguished from other early mammaliaforms by their relatively complex [[Molar (tooth)|molar]] teeth. Docodont teeth have been described as "pseudotribosphenic": a cusp on the inner half of the upper molar grinds into a basin on the front half of the lower molar, like a [[Mortar and pestle|mortar-and-pestle]]. This is a case of [[convergent evolution]] with the [[Tribosphenic molar|tribosphenic]] teeth of therian mammals. There is much uncertainty for how docodont teeth developed from their simpler ancestors. Their closest relatives may have been certain Triassic "[[Symmetrodonta|symmetrodonts]]", namely ''[[Woutersia]]'', and ''[[Delsatia]]''.<ref name=":0">{{Cite journal|last1=Luo|first1=Zhe-Xi|last2=Martin|first2=Thomas|date=2007|title=Analysis of Molar Structure and Phylogeny of Docodont Genera|url=https://www.researchgate.net/publication/232685604|journal=Bulletin of Carnegie Museum of Natural History|volume=2007|issue=39|pages=27–47|doi=10.2992/0145-9058(2007)39[27:AOMSAP]2.0.CO;2|s2cid=29846648 |issn=0145-9058}}</ref> The [[Shuotheriidae|shuotheriids]], another group of Jurassic mammaliaforms, also shared some dental characteristics with docodonts. One study has suggested that shuotheriids are closely related to docodonts,<ref name=":13">{{Cite journal |last=Mao |first=Fangyuan |last2=Li |first2=Zhiyu |last3=Wang |first3=Zhili |last4=Zhang |first4=Chi |last5=Rich |first5=Thomas |last6=Vickers-Rich |first6=Patricia |last7=Meng |first7=Jin |date=2024-04-03 |title=Jurassic shuotheriids show earliest dental diversification of mammaliaforms |url=https://www.nature.com/articles/s41586-024-07258-7 |journal=Nature |language=en |doi=10.1038/s41586-024-07258-7 |issn=0028-0836}}</ref> though others consider shuotheriids to be true mammals, perhaps related to to [[Monotreme|monotremes]].<ref name=":14" /> For much of their history of study, docodont fossils were represented by isolated teeth and jaws. The first docodont known from decent remains was ''[[Haldanodon]]'', from the [[Guimarota]] site of [[Portugal]]. Recently, exceptionally preserved skeletons have been discovered in the [[Tiaojishan Formation]] of [[China]]. Chinese docodonts include [[otter]]-like,<ref name=":3" /> [[Mole (animal)|mole]]-like,<ref name=":1">{{Cite journal|last1=Luo|first1=Zhe-Xi|last2=Meng|first2=Qing-Jin|last3=Ji|first3=Qiang|last4=Liu|first4=Di|last5=Zhang|first5=Yu-Guang|last6=Neander|first6=April I.|date=2015-02-13|title=Evolutionary development in basal mammaliaforms as revealed by a docodontan|url=https://www.science.org/doi/abs/10.1126/science.1260880|journal=Science|volume=347|language=EN|issue=6223|pages=760–764|doi=10.1126/science.1260880|pmid=25678660|bibcode=2015Sci...347..760L |s2cid=206562572}}</ref> and [[squirrel]]-like species,<ref name=":2">{{Cite journal|last1=Meng|first1=Qing-Jin|last2=Ji|first2=Qiang|last3=Zhang|first3=Yu-Guang|last4=Liu|first4=Di|last5=Grossnickle|first5=David M.|last6=Luo|first6=Zhe-Xi|date=2015-02-13|title=An arboreal docodont from the Jurassic and mammaliaform ecological diversification|url=https://www.researchgate.net/publication/272185207|journal=Science|language=EN|volume=347|issue=6223|pages=764–768|doi=10.1126/science.1260879|pmid=25678661|bibcode=2015Sci...347..764M |s2cid=206562565}}</ref><ref name=":10" /> hinting at impressive ecological diversity within the group. Many docodonts have muscular limbs and broad tail vertebrae, adaptations for burrowing or swimming. Like true mammals, docodonts have hair,<ref name=":3" /> a saddle-shaped [[hyoid apparatus]],<ref name=":10" /> and reduced postdentary jaw bones which are beginning to develop into [[middle ear ossicles]]. On the other hand, the postdentary bones are still attached to the jaw and skull, the nostrils have yet to fuse, and in most species the [[Vertebral column|spine's]] [[Thoracic vertebrae|thoracic]]-[[Lumbar vertebrae|lumbar]] transition is rather subdued.<ref name=":1" /><ref name=":2" /> Line 63: "Pseudotalonid" and "pseudoprotocone" are names which reference the [[talonid]]-and-[[protocone]] crushing complex which characterize [[Tribosphenic molar|tribosphenic teeth]]. Tribosphenic teeth show up in the oldest fossils of [[theria]]ns, the mammalian subgroup containing [[marsupial]]s and [[Placentalia|placentals]]. This is a case of [[convergent evolution]], as therian talonids lie at the back of the lower molar rather than the front. The opposite is true for docodont teeth, which have been described as "pseudotribosphenic".<ref name=":0" /> Pseudotribosphenic teeth are also found in [[Shuotheriidae|shuotheriids]], an unusual collection of Jurassic mammals with tall pointed cusps. Relative to docodonts, shuotheriids have pseudotalonids which are positioned further forwards in their lower molars. This is potentially another case of convergent evolution, as shuotheriid are often considered true mammals related to modern [[monotreme]]s.<ref name=":14">{{Cite book|last1=Martin|first1=Thomas|title=Mammalian Teeth - Form and Function|last2=Jäger|first2=Kai R. K.|last3=Plogschties|first3=Thorsten|last4=Schwermann|first4=Achim H.|last5=Brinkkötter|first5=Janka J.|last6=Schultz|first6=Julia A.|publisher=Verlag Dr. Friedrich Pfeil|year=2020|editor-last=Martin|editor-first=Thomas|location=München, Germany|pages=187–214|chapter=Molar diversity and functional adaptations in Mesozoic mammals|editor-last2=von Koenigswald|editor-first2=Wighart|chapter-url=https://pfeil-verlag.de/wp-content/uploads/2020/12/10.23788mammteeth.10.pdf}}</ref> Docodont and shuotheriid teeth are so similar that some genera, namely ''[[Itatodon]]'' and ''[[Paritatodon]]'', have been considered members of either group.<ref name=":7">{{Cite journal|last1=Averianov|first1=A. O.|last2=Lopatin|first2=A. V.|date=December 2006|title=''Itatodon tatarinovi'' (Tegotheriidae, Mammalia), a docodont from the Middle Jurassic of Western Siberia and phylogenetic analysis of Docodonta|journal=Paleontological Journal|volume=40|issue=6|pages=668–677|doi=10.1134/s0031030106060098|bibcode=2006PalJ...40..668A |issn=0031-0301|s2cid=129438779}}</ref><ref name=":8">{{Cite journal|last1=Wang|first1=Yuan-Qing|last2=Li|first2=Chuan-Kui|date=2016|title=Reconsideration of the systematic position of the Middle Jurassic mammaliaforms Itatodon and Paritatodon|url=http://www.palaeontologia.pan.pl/PP67/Wang.pdf|journal=Palaeontologia Polonica|volume=67|pages=249–256|doi=10.4202/pp.2016.67_249|doi-broken-date=2024-09-12}}</ref> A 2024 study, describing the new shuotheriid ''[[Feredocodon]]'', even proposed that shuotheriids and docodonts were most closely related to each other among mammaliaforms. The study named a new clade, Docodontiformes, to encompass the two groups.<ref name=":13" /> === Metabolism and Lifespan === Line 112: |2=[[Theriimorpha]] (including [[Metatheria]] and [[Eutheria]]) }} }} }} }} }} }} }} Docodont fossils have been recognized since the 1880s, but their relationships and diversity have only recently been well-established. [[Monograph]]s by [[George Gaylord Simpson]] in the 1920s argued that they were specialized "[[Pantotheria|pantotheres]]", part of a broad group ancestral to true therian mammals according to their complex molars.<ref>{{Cite journal|last=Simpson|first=George Gaylord|date=1928|title=A Catalogue of the Mesozoic Mammalia in the Geological Department of the British Museum|url=https://www.biodiversitylibrary.org/item/207020#page/7/mode/1up|journal=Trustees of the British Museum, London|pages=1–215}}</ref><ref name=":4">{{Cite journal|last=Simpson|first=George Gaylord|date=1929|title=American Mesozoic Mammalia|url=https://www.biodiversitylibrary.org/item/26623#page/11/mode/1up|journal=Memoirs of the Peabody Museum of Yale University|volume=3|issue=1|pages=1–235}}</ref> A 1956 paper by [[Bryan Patterson]] instead argued that docodont teeth were impossible to homologize with modern mammals. He drew comparisons to the teeth of ''[[Morganucodon]]'' and other "[[triconodont]]" mammaliaforms, which had fairly simple lower molars with a straight row of large cusps.<ref>{{Cite journal|last=Patterson|first=Bryan|date=1956|title=Early Cretaceous mammals and the evolution of mammalian molar teeth|url=https://www.biodiversitylibrary.org/item/21537#page/19/mode/1up|journal=Fieldiana|volume=13|issue=1|pages=1–105}}</ref> However, re-evaluations of mammaliaform tooth homology in the late 1990s established that docodonts were not closely related to either morganucodonts or therians.<ref>{{Cite journal|last1=Sigogneu-Russell|first1=Denise|last2=Hahn|first2=Renate|date=1995|title=Reassessment of the late Triassic symmetrodont mammal ''Woutersia''|url=https://www.app.pan.pl/archive/published/app40/app40-245.pdf|journal=Acta Palaeontologica Polonica|volume=40|issue=3|pages=245–260}}</ref><ref name=":5">{{Cite journal|last=Butler|first=P. M.|date=1997-06-19|title=An alternative hypothesis on the origin of docodont molar teeth|url=https://www.tandfonline.com/doi/10.1080/02724634.1997.10010988|journal=Journal of Vertebrate Paleontology|volume=17|issue=2|pages=435–439|doi=10.1080/02724634.1997.10010988|issn=0272-4634|jstor=4523820|bibcode=1997JVPal..17..435B }}</ref> Instead, they were found to be similar to certain early "[[Symmetrodonta|symmetrodonts]]", a broad and polyphyletic grouping of mammaliaforms with triangular upper molars.<ref name=":5" /> In particular, the closest relatives of Docodonta have been identified as certain Late Triassic "symmetrodonts", such as ''[[Delsatia]]'' and ''[[Woutersia]]'' (from the [[Norian]]-[[Rhaetian]] of [[France]]).<ref name=":0" /><ref>{{Citation|last1=Abdala|first1=Fernando|title=The Late Triassic Record of Cynodonts: Time of Innovations in the Mammalian Lineage|date=2018|url=https://doi.org/10.1007/978-3-319-68009-5_11|work=The Late Triassic World: Earth in a Time of Transition|pages=407–445|editor-last=Tanner|editor-first=Lawrence H.|series=Topics in Geobiology|place=Cham|publisher=Springer International Publishing|language=en|doi=10.1007/978-3-319-68009-5_11|isbn=978-3-319-68009-5|access-date=2022-01-29|last2=Gaetano|first2=Leandro C.}}</ref> These "symmetrodonts" have three major cusps (c, a, and b) set in a triangular arrangement on their lower molars. These cusps would be homologous to cusps c, a, and g in docodonts, which have a similar size and position. Unambiguous docodonts are restricted to the [[Northern Hemisphere]], abruptly appearing in the fossil record in the [[Middle Jurassic]]. Very few docodonts survived into the [[Cretaceous period|Cretaceous Period]]; the youngest known members of the group are ''[[Sibirotherium]]'' and ''[[Khorotherium]]'', from the [[Early Cretaceous]] of [[Siberia]].<ref name=":9" /><ref>{{Cite journal|last1=Lopatin|first1=A. V.|last2=Averianov|first2=A. O.|last3=Kuzmin|first3=I. T.|last4=Boitsova|first4=E. A.|last5=Saburov|first5=P. G.|last6=Ivantsov|first6=S. V.|last7=Skutschas|first7=P. P.|date=2020|title=A New Finding of a Docodontan (Mammaliaformes, Docodonta) in the Lower Cretaceous of Western Siberia|url=https://link.springer.com/10.1134/S1028334X20090123|journal=Doklady Earth Sciences|language=en|volume=494|issue=1|pages=667–669|doi=10.1134/S1028334X20090123|bibcode=2020DokES.494..667L |s2cid=224811982|issn=1028-334X}}</ref> One disputed docodont, ''[[Gondtherium]]'', has been described from India, which was previously part of the [[Southern Hemisphere]] continent of [[Gondwana]].<ref name="PrasadManhas2007">Prasad GVR, and Manhas BK. 2007. A new docodont mammal from the Jurassic Kota Formation of India. Palaeontologia electronica, 10.2: 1-11.</ref><ref name=":0" /> However, this identification is not certain, and in recent analyses, ''Gondtherium'' falls outside the docodont family tree, albeit as a close relative to the group.<ref name=":2" /><ref name=":10">{{cite journal|last1=Zhou|first1=Chang-Fu|last2=Bhullar|first2=Bhart-Anjan|last3=Neander|first3=April|last4=Martin|first4=Thomas|last5=Luo|first5=Zhe-Xi|date=19 Jul 2019|title=New Jurassic mammaliaform sheds light on early evolution of mammal-like hyoid bones|journal=Science|volume=365|issue=6450|pages=276–279|bibcode=2019Sci...365..276Z|doi=10.1126/science.aau9345|pmid=31320539|s2cid=197663503}}</ref> ''[[Reigitherium]]'', from the [[Late Cretaceous]] of [[Argentina]], has previously been described as a docodont,<ref>{{Cite journal|last1=Pascual|first1=Rosendo|last2=Goin|first2=Francisco J.|last3=Gonzalez|first3=Pablo|last4=Ardolino|first4=Alberto|last5=Puerta|first5=Pablo F.|date=2000|title=A highly derived docodont from the Patagonian Late Cretaceous: evolutionary implications for Gondwanan mammals|url=https://www.researchgate.net/publication/237760695|journal=Geodiversitas|language=en|volume=22|issue=3|pages=395–414}}</ref> though it is now considered a [[meridiolestida]]n mammal.<ref>{{Cite journal|last1=Harper|first1=Tony|last2=Parras|first2=Ana|last3=Rougier|first3=Guillermo W.|date=2019-12-01|title=Reigitherium (Meridiolestida, Mesungulatoidea) an Enigmatic Late Cretaceous Mammal from Patagonia, Argentina: Morphology, Affinities, and Dental Evolution|url=https://doi.org/10.1007/s10914-018-9437-x|journal=Journal of Mammalian Evolution|language=en|volume=26|issue=4|pages=447–478|doi=10.1007/s10914-018-9437-x|s2cid=21654055|issn=1573-7055|hdl=11336/81478|hdl-access=free}}</ref> Some authors have suggested splitting Docodonta into two families (Simpsonodontidae and Tegotheriidae),<ref>L. P. Tatarinov (1994). "On an unusual mammalian tooth from the Mongolian Jurassic". Journal of the Geological Society of London. 128: 119–125.</ref><ref name=":7" /><ref name="Averianov2010">{{Cite journal|author1=Averianov, A. A. |author2=Lopatin, A. V. |author3=Krasnolutskii, S. A. |author4=Ivantsov, S. V. |year=2010|title=New docodontians from the Middle Jurassic of Siberia and reanalysis of docodonta interrelationships|url=http://www.zin.ru/journals/trudyzin/doc/vol_314_2/TZ_314_2_Averianov.pdf|journal=Proceedings of the Zoological Institute RAS|volume=314|issue=2|pages=121–148|doi=10.31610/trudyzin/2010.314.2.121 |s2cid=35820076 }}</ref> but the [[monophyly]] of these groups (in their widest form) are not found in any other analyses, and therefore not accepted by all mammal palaeontologists.<ref>{{Cite journal|last1=Panciroli|first1=Elsa|last2=Benson|first2=Roger B. J.|last3=Luo|first3=Zhe-Xi|date=2019-05-04|title=The mandible and dentition of ''Borealestes serendipitus'' (Docodonta) from the Middle Jurassic of Skye, Scotland|url=https://www.tandfonline.com/doi/full/10.1080/02724634.2019.1621884|journal=Journal of Vertebrate Paleontology|language=en|volume=39|issue=3|pages=e1621884|doi=10.1080/02724634.2019.1621884|bibcode=2019JVPal..39E1884P |hdl=20.500.11820/75714386-2baa-4512-b4c8-add5719f129b|s2cid=199637122|issn=0272-4634|hdl-access=free}}</ref> | |||