Metatheria

{{Short description|Clade of marsupials and close relatives}} {{Use dmy dates|date=May 2024}} {{Automatic taxobox | fossil_range = {{Fossil range|Albian|earliest=Aptian|Recent|Early Cretaceous–recent<ref name="SCI-20130208">{{cite journal |last1=O'Leary |first1=Maureen A. |last2=Bloch |first2=Jonathan I. |last3=Flynn |first3=John J. |last4=Gaudin |first4=Timothy J. |last5=Giallombardo |first5=Andres |last6=Giannini |first6=Norberto P. |last7=Goldberg |first7=Suzann L. |last8=Kraatz |first8=Brian P. |last9=Luo |first9=Zhe-Xi |last10=Meng |first10=Jin |last11=Ni |first11=Michael J. |last12=Novacek |first12=Fernando A. |last13=Perini |first13=Zachary S. |last14=Randall |first14=Guillermo |last15=Rougier |first15=Eric J. |last16=Sargis |first16=Mary T. |last17=Silcox |first17=Nancy b. |last18=Simmons |first18=Micelle |last19=Spaulding |first19=Paul M. |last20=Velazco |first20=Marcelo |last21=Weksler |first21=John R. |last22=Wible |first22=Andrea L. |title=The Placental Mammal Ancestor and the Post–K-Pg Radiation of Placentals |date=8 February 2013 |journal=Science |volume=339 |pages=662–667 |doi=10.1126/science.1229237 |pmid=23393258 |issue=6120 |last23=Cirranello |first23=A. L.|bibcode=2013Sci...339..662O |s2cid=206544776 |hdl=11336/7302 |hdl-access=free }}</ref><ref name="Bennett_2018">{{cite journal | title = Deep time diversity of metatherian mammals: implications for evolutionary history and fossil-record quality | journal = Paleobiology | volume = 44 | issue = 2 | date = 2018 |author=C.V. Bennett |author2=P. Francisco |author3=F. J. Goin |author4=A. Goswami | doi = 10.1017/pab.2017.34 | pages= 171–198 | doi-access = free | bibcode = 2018Pbio...44..171B | hdl = 11336/94590 | hdl-access = free }}</ref><ref name="Bi_2018">{{cite journal | title = An Early Cretaceous eutherian and the placental–marsupial dichotomy | journal = Nature | volume = 558 | issue = 7710 | pages = 390–395 | date = 2018 |author=S. Bi |author2=X. Zheng |author3=X. Wang |author4=N.E. Cignetti |author5=S. Yang |author6=J.R. Wible | doi = 10.1038/s41586-018-0210-3 | pmid = 29899454 | bibcode = 2018Natur.558..390B | s2cid = 49183466 }}</ref> }} | image = Lycopsis longirostris.JPG | image_caption = ''Lycopsis longirostris'', an extinct sparassodont, a relative of the marsupials | image2 = Mouse Possum -Tambopata Reserve -Peru-8.jpg | image2_caption = A mouse opossum (''Marmosa'') | taxon = Metatheria | authority = Huxley, 1880 | subdivision_ranks = Subgroups | subdivision = *{{extinct}}''?Sinodelphys'' *{{extinct}}''Holoclemensia'' *{{extinct}}''Adinodon'' *{{extinct}}Deltatheroida *'''Marsupialiformes''' **{{extinct}}''Adelodelphys'' **{{extinct}}Alphadontidae **{{extinct}}Asiadelphia **{{extinct}}''Sinbadelphys'' **{{extinct}}''Camptomus''? **{{extinct}}'''Archimetatheria''' ***{{extinct}}Stagodontidae ***{{extinct}}''Iqualadelphis'' **{{extinct}}Sparassodonta **{{extinct}}Pucadelphyidae **{{extinct}}Herpetotheriidae **{{extinct}}Anatoliadelphyidae **{{extinct}}Polydolopimorphia **{{extinct}}Peradectidae **{{extinct}}Pediomyidae **Marsupialia }}

'''Metatheria''' is a mammalian clade that includes all mammals more closely related to marsupials than to placentals. First proposed by Thomas Henry Huxley in 1880, it is a more inclusive group than the marsupials; it contains all marsupials as well as many extinct non-marsupial relatives. It is one of two groups placed in the clade Theria alongside Eutheria, which contains the placentals. Remains of metatherians have been found on all of Earth's continents.

== Description == Distinctive characteristics (synapomorphies) of Metatheria include a prehensile tail, the development of a capitular tail on the humerus, the loss of tooth replacement on the second and fifth premolars, lower canines that outwardly diverge from each other, an angular process on the dentary bone—which additionally bears a posterior shelf in its masseteric fossa in Metatheria<ref name=":2">{{Cite journal |last1=Williamson |first1=Thomas E. |last2=Brusatte |first2=Stephen L. |last3=Wilson |first3=Gregory P. |date=17 December 2014 |title=The origin and early evolution of metatherian mammals: the Cretaceous record |journal=ZooKeys |issue=465 |pages=1–76 |doi=10.3897/zookeys.465.8178 |doi-access=free |issn=1313-2970 |pmc=4284630 |pmid=25589872|bibcode=2014ZooK..465....1W }}</ref>—that is equal to or greater than the length of the ramus,<ref name=":2"/><ref>{{cite journal|last1=Wible|first1=John R.|last2=Rougier|first2=Guillermo R.|last3=Novacek|first3=Michael J.|last4=Asher|first4=Robert J.|title=The Eutherian Mammal ''Maelestes gobiensis'' from the Late Cretaceous of Mongolia and the phylogeny of cretaceous eutheria|journal=Bulletin of the American Museum of Natural History|volume=2009|issue=327|year=2009|pages=1–123|doi=10.1206/623.1|doi-access=free}}</ref>{{rp|Appendix 2}} and the lower fifth premolar with a "very trenchant"<ref name=":2"/> cristid obliqua/ectolophid. The permanent, retained deciduous fifth premolars are molar like and were historically identified as first molars, with the third premolar found in basal therians being lost, leaving four premolars in the halves of each jaw.<ref name=":2"/> ''Sinodelphys'' differs in its dentition and may represent a basal metatherian.<ref name=":2"/>

== Evolutionary history == The relationships between the three extant divisions of mammals (monotremes, marsupials, and placentals) was long a matter of debate among taxonomists.<ref name="Moyal2004">{{cite book |author=Moyal, Ann Mozley |url=https://books.google.com/books?id=5DkezNMhSTYC |title=Platypus: The Extraordinary Story of How a Curious Creature Baffled the World |publisher=The Johns Hopkins University Press |year=2004 |isbn=978-0-8018-8052-0 |location=Baltimore}}</ref> Most morphological evidence comparing traits, such as the number and arrangement of teeth and the structure of the reproductive and waste elimination systems, favors a closer evolutionary relationship between marsupials and placental mammals than either has with the monotremes, as does most genetic and molecular evidence.<ref name="Rheede2005">{{Cite journal |last1=van Rheede |first1=T. |last2=Bastiaans |first2=T. |last3=Boone |first3=D. |last4=Hedges |first4=S. |last5=De Jong |first5=W. |last6=Madsen |first6=O. |year=2006 |title=The platypus is in its place: nuclear genes and indels confirm the sister group relation of monotremes and therians |journal=Molecular Biology and Evolution |volume=23 |issue=3 |pages=587–597 |doi=10.1093/molbev/msj064 |pmid=16291999 |doi-access=free}}</ref>

The earliest possible known metatherian is ''Sinodelphys szalayi'', which lived in China during the Early Cretaceous around 125 million years ago (mya).<ref name=":2"/><ref>{{cite web |last=Rincon |first=Paul |date=12 December 2003 |title=Oldest Marsupial Ancestor Found, BBC, Dec 2003 |url=https://news.bbc.co.uk/2/hi/science/nature/3311911.stm |access-date=16 March 2010 |publisher=BBC News}}</ref> This makes it a contemporary to some early eutherian species that have been found in the same area.<ref name="acristatherium">{{cite journal |last1=Hu |first1=Yaoming |last2=Meng |first2=Jin |last3=Li |first3=Chuankui |last4=Wang |first4=Yuanqing |year=2010 |title=New basal eutherian mammal from the Early Cretaceous Jehol biota, Liaoning, China |journal=Proceedings of the Royal Society B |volume=277 |issue=1679 |pages=229–236 |doi=10.1098/rspb.2009.0203 |pmc=2842663 |pmid=19419990}}</ref> However, Bi ''et al.'' (2018) reinterpreted ''Sinodelphys'' as an early member of Eutheria. The oldest uncontested metatherians are now 110 million year old fossils from western North America.<ref name="Bi_2018" /> Metatherians were widespread in Asia and North America during the Late Cretaceous, including both Deltatheroida and Marsupialiformes,<ref name=":0" /> with fossils also known from Europe during this time. During the Late Cretaceous, metatherians were more diverse than eutherians in North America.<ref name=":2" /> Metatherians underwent a severe decline during the Cretaceous–Paleogene extinction event, more severe than that suffered by contemporary eutherians and multituberculates, and were slower to recover diversity.<ref name=":0">{{Cite journal |last1=Bennett |first1=C. Verity |last2=Upchurch |first2=Paul |last3=Goin |first3=Francisco J. |last4=Goswami |first4=Anjali |date=6 February 2018 |title=Deep time diversity of metatherian mammals: implications for evolutionary history and fossil-record quality |journal=Paleobiology |volume=44 |issue=2 |pages=171–198 |bibcode=2018Pbio...44..171B |doi=10.1017/pab.2017.34 |issn=0094-8373 |s2cid=46796692 |doi-access=free |hdl-access=free |hdl=11336/94590}}</ref>

Morphological and species diversity of metatherians in Laurasia remained low in comparison to eutherians throughout the Cenozoic.<ref name=":1">{{Cite journal |last1=Eldridge |first1=Mark D B |last2=Beck |first2=Robin M D |last3=Croft |first3=Darin A |last4=Travouillon |first4=Kenny J |last5=Fox |first5=Barry J |date=23 May 2019 |title=An emerging consensus in the evolution, phylogeny, and systematics of marsupials and their fossil relatives (Metatheria) |url=https://academic.oup.com/jmammal/article/100/3/802/5498022 |journal=Journal of Mammalogy |language=en |volume=100 |issue=3 |pages=802–837 |doi=10.1093/jmammal/gyz018 |issn=0022-2372}}</ref> The two major groups of Cenozoic Laurasian metatherians, the opossum-like herpetotheriids and peradectids persisted into the Miocene before becoming extinct, with the North American herpetotheriid ''Herpetotherium'', the European herpetotheriid ''Amphiperatherium'' and the peradectids ''Siamoperadectes'' and ''Sinoperadectes'' from Asia being the youngest Laurasian non-marsupial metatherians (with marsupials invading North America during the Pliocene-Pleistocene as part of the Great American interchange).<ref>{{Cite journal |last1=Furió |first1=Marc |last2=Ruiz-Sánchez |first2=Francisco J. |last3=Crespo |first3=Vicente D. |last4=Freudenthal |first4=Matthijs |last5=Montoya |first5=Plinio |date=July 2012 |title=The southernmost Miocene occurrence of the last European herpetotheriid Amphiperatherium frequens (Metatheria, Mammalia) |url=https://www.sciencedirect.com/science/article/pii/S1631068312000504 |journal=Comptes Rendus Palevol |language=en |volume=11 |issue=5 |pages=371–377 |bibcode=2012CRPal..11..371F |doi=10.1016/j.crpv.2012.01.004 |access-date=26 October 2024 |via=Elsevier Science Direct|url-access=subscription }}</ref><ref name=":0" /> Metatherians first arrived in Afro-Arabia during the Paleogene, probably from Europe, including the possible peradectoid ''Kasserinotherium'' from the Early Eocene of Tunisia and the herpetotheriid ''Peratherium africanum'' from the Early Oligocene of Egypt and Oman. The youngest African metatherian is the possible herpetotheriid ''Morotodon'' from the late Early Miocene of Uganda.<ref>{{Cite journal |last1=Crespo |first1=Vicente D. |last2=Goin |first2=Francisco J. |date=21 June 2021 |title=Taxonomy and Affinities of African Cenozoic Metatherians |url=https://ojs.uv.es/index.php/sjpalaeontology/article/view/20974 |journal=Spanish Journal of Palaeontology |volume=36 |issue=2 |pages=133–148 |doi=10.7203/sjp.36.2.20974 |issn=2255-0550 |s2cid=237387495 |doi-access=free |hdl-access=free |hdl=11336/165007}}</ref><ref>{{Cite journal |last1=Crespo |first1=Vicente D. |last2=Goin |first2=Francisco J. |last3=Pickford |first3=Martin |date=3 June 2022 |title=The last African metatherian |url=https://fr.pensoft.net/article/80706/ |journal=Fossil Record |volume=25 |issue=1 |pages=173–186 |doi=10.3897/fr.25.80706 |issn=2193-0074 |s2cid=249349445 |doi-access=free |hdl-access=free |hdl=10362/151025}}</ref>

Metatherians arrived in South America from North America during the latest Cretaceous or Paleocene and underwent a major diversificiation, with South American metatherians including both the ancestors of extant marsupials as well as the extinct Sparassodonta, which were major predators in South American ecosystems during most of the Cenozoic, up until their extinction in the Pliocene, as well as the Polydolopimorphia, which likely had a wide range of diets.<ref name=":1" /> Metatherians then declined in diversity in South America during the Late Eocene as well as the later Oligocene epoch. The oldest known Australian marsupials are from the early Eocene, and are thought to have arrived in the region after having dispersed via Antarctica from South America.<ref name=":1" /> During the Oligocene epoch, Australian metatherians radiated rapidly, which contributed most to the global peak in metatherian diversity during the Early Miocene. The only known Antarctic metatherians are from the Early Eocene La Meseta Formation of the Antarctic Peninsula, where they are the most diverse group of mammals, and include marsupials as well as polydolopimorphians.<ref name=":1" />

==Classification== Below is a metatherian cladogram from Wilson et al. (2016):<ref name="wilson2016">{{cite journal |last1=Wilson |first1=G.P. |last2=Ekdale |first2=E.G. |last3=Hoganson |first3=J.W. |last4=Calede |first4=J.J. |last5=Linden |first5=A.V. |date=December 2016 |title=A large carnivorous mammal from the Late Cretaceous and the North American origin of marsupials |url=https://www.researchgate.net/publication/311523654 |journal=Nature Communications |volume=7 |article-number=13734 |bibcode=2016NatCo...713734W |doi=10.1038/ncomms13734 |pmc=5155139 |pmid=27929063 |access-date=26 October 2024 |via=ResearchGate}}</ref>

{{clade| style=font-size:85%; line-height:85% |label1=Metatheria |1={{clade |1={{extinct}}''Holoclemensia'' |2={{clade |label1={{extinct}}Deltatheroida |1={{clade |label1={{extinct}}Pappotheriidae |1={{extinct}}''Pappotherium'' |label2={{extinct}}Deltatheridiidae |2={{clade |1={{extinct}}''Sulestes'' |2={{extinct}}''Oklatheridium'' |3={{clade |1={{extinct}}''Tsagandelta'' |2={{clade |1={{extinct}}''Lotheridium'' |2={{clade |1={{extinct}}''Deltatheroides'' |2={{extinct}}''Deltatheridium'' |3={{clade |1={{extinct}}''Nanocuris'' |2={{extinct}}''Atokatheridium'' }} }} }} }} }} }} |label2=Marsupialiformes |2={{clade |1={{clade |1={{extinct}}Gurlin Tsav skull |2={{clade |1={{extinct}}Borhyaenidae |2={{clade |1={{extinct}}''Mayulestes'' |2={{clade |1={{extinct}}''Jaskhadelphys'' |2={{clade |1={{extinct}}''Andinodelphys'' |2={{extinct}}''Pucadelphys'' }} }} }} }} }} |2={{clade |1={{extinct}}''Asiatherium'' |2={{clade |1={{clade |1={{extinct}}''Iugomortiferum'' |2={{extinct}}''Kokopellia'' }} |2={{extinct}}''Aenigmadelphys'' |3={{extinct}}''Anchistodelphys'' |4={{clade |label1={{extinct}}Glasbiidae |label2={{extinct}}Pediomyidae |1={{extinct}}''Glasbius'' |2={{extinct}}''Pediomys'' }} |label5={{extinct}}Stagodontidae |5={{clade |1={{extinct}}''Pariadens'' |2={{clade |1={{extinct}}''Eodelphis'' |2={{extinct}}''Didelphodon'' }} }} |grouplabel7=Alphadontidae |barbegin6=green |6={{extinct}}''Turgidodon'' |bar6=green |7={{extinct}}''Alphadon'' |bar7=green |8={{extinct}}''Albertatherium'' |barend8=green |9=Marsupialia }} }} }} }} }} }}Cladogram according to Ladevèze et al. 2020:<ref>{{Cite journal |last1=Ladevèze |first1=Sandrine |last2=Selva |first2=Charlène |last3=de Muizon |first3=Christian |date=1 September 2020 |title=What are "opossum-like" fossils? The phylogeny of herpetotheriid and peradectid metatherians, based on new features from the petrosal anatomy |url=https://www.tandfonline.com/doi/full/10.1080/14772019.2020.1772387 |journal=Journal of Systematic Palaeontology |language=en |volume=18 |issue=17 |pages=1463–1479 |doi=10.1080/14772019.2020.1772387 |bibcode=2020JSPal..18.1463L |issn=1477-2019 |access-date=26 October 2024 |via=Taylor and Francis Online}}</ref>{{clade |label1=Metatheria |1={{clade |1={{extinct}}Deltatheriidae |2={{clade |1={{extinct}}''Kokopellia'' |2={{clade |1={{extinct}}''Asiatherium'' |2={{clade |1={{extinct}}Peradectidae |2={{clade |1={{extinct}}Stagodontidae |2={{clade |1={{clade |1={{extinct}}Pucadelphyidae |2={{extinct}}Sparassodonta }} |2={{clade |barbegin1=green |grouplabel1="Herpetotheriidae" |1={{clade |1={{extinct}}''Amphiperatherium'' |2={{extinct}}''Peratherium'' }} |2={{clade |1={{extinct}}''Herpetotherium'' |barend1=green |2=Marsupialia }}}}}}}}}}}}}}}}}}

Below is a listing of metatherians that do not fall readily into well-defined groups.

Basal Metatheria *†''Archaeonothos henkgodthelpi'' Beck 2015 *†''Esteslestes ensis'' Novacek et al. 1991 *†''Ghamidtherium dimaiensis'' Sánches-Villagra et al. 2007 *†''Kasserinotherium tunisiense'' Crochet 1989 *†''Palangania brandmayri'' Goin et al. 1998 *†''Perrodelphys coquinense'' Goin et al. 1999

Ameridelphia incertae sedis: *†''Apistodon exiguus'' (Fox 1971) Davis 2007 *†''Cocatherium lefipanum'' Goin et al. 2006 *†''Dakotadens morrowi'' Eaton 1993 *†''Iugomortiferum thoringtoni'' Cifelli 1990b *†''Marambiotherium glacialis'' Goin et al. 1999 *†''Marmosopsis juradoi'' Paula Couto 1962 [Marmosopsini Kirsch & Palma 1995] *†''Pascualdelphys fierroensis'' *†''Progarzonia notostylopense'' Ameghino 1904 *†''Protalphadon'' Cifelli 1990 **†''P. lulli'' (Clemens 1966) Cifelli 1990a **†''P. foxi'' Johnson 1996

Marsupialia incertae sedis: *†''Itaboraidelphys camposi'' Marshall & de Muizon 1984 *†''Mizquedelphys pilpinensis'' Marshall & de Muizon 1988 *†''Numbigilga ernielundeliusi'' Beck et al. 2008 {Numbigilgidae Beck et al. 2008}

==References== {{Reflist|25em}} {{Commons category|Metatheria}}

Category:Metatheria Category:Early Cretaceous mammals Category:Cretaceous mammals Category:Paleogene mammals Category:Neogene mammals Category:Quaternary mammals Category:Prehistoric marsupials Category:Extant Early Cretaceous first appearances Category:Mammal unranked clades