Editing Repenomamus

{{Short description|Extinct genus of mammals}}
{{automatic Taxobox
| fossil_range = [[Early Cretaceous]], {{fossilrange|125|123.2}}
| image = Repenomamus-Paleozoological Museum of China.jpg
| image_caption = Type of ''R''. ''giganticus'', [[Paleozoological Museum of China]]
| taxon = Repenomamus
| authority = Li ''et al.'', 2001
| type_species = {{extinct}}'''''Repenomamus robustus'''''
| type_species_authority = Li ''et al.'', 2001<ref name="Li et al 2001">{{cite journal|title=A new family of primitive mammal from the Mesozoic of western Liaoning, China|journal=Chinese Science Bulletin|date=2001|volume=46|issue=9|pages=782–785|author=Li|doi=10.1007/bf03187223|bibcode=2001ChSBu..46..782L|s2cid=129025369|display-authors=etal}}</ref>
| subdivision_ranks = [[Species]]
| subdivision = {{extinct}}'''''Repenomamus robustus''''' <small>Li ''et al.'', 2000</small><br />
{{extinct}}'''''Repenomamus giganticus''''' <small>Hu ''et al.'', 2005</small>
}}

'''''Repenomamus''''' (Latin: "reptile" (reptilis), "mammal" (mammalis)<ref>{{cite web|url=https://research.amnh.org/paleontology/perissodactyl/concepts/glossary|archive-url=https://web.archive.org/web/20211120123130/https://research.amnh.org/paleontology/perissodactyl/concepts/glossary|archive-date=20 November 2021|title=Glossary. American Museum of Natural History}}</ref>) is a genus of opossum- to badger-sized [[Gobiconodontidae|gobiconodontid]]<ref name="Montellano2008">{{Cite journal|author=Marisol Montellano |author2=James A. Hopson |author3=James M. Clark |year=2008|title=Late Early Jurassic Mammaliaforms from Huizachal Canyon, Tamaulipas, México|journal=Journal of Vertebrate Paleontology|volume=28|issue=4|pages=1130–1143 |doi=10.1671/0272-4634-28.4.1130|bibcode=2008JVPal..28.1130M |s2cid=128782275}}</ref> [[mammal]] containing two species, '''''Repenomamus robustus''''' and '''''Repenomamus giganticus'''''. Both species are known from fossils found in [[China]] that date to the early [[Cretaceous]] period, about 125-123.2 million years ago.  ''R. robustus'' is one of several Mesozoic mammals{{refn|Other [[eutriconodont]]s and [[Deltatheroida|deltatheroidean]] [[metatheria]]ns have adaptations towards specialised carnivory<ref>{{cite journal |vauthors=Wilson Gregory P, Riedel Jeremy A | year = 2010 | title = New Specimen Reveals Delta Theroidan Affinities of the North American Late Cretaceous Mammal Nanocuris | journal = Journal of Vertebrate Paleontology | volume = 30 | issue = 3| pages = 872–884 | doi = 10.1080/02724631003762948 | bibcode = 2010JVPal..30..872W | s2cid = 53524747 }}</ref><ref>{{cite journal | author = Christian DE MUIZON, Brigitte LANGE-BADRÉ | year = 2007| title = Carnivorous dental adaptations in tribosphenic mammals and phylogenetic reconstruction | journal = Lethaia| volume =  30| issue = 4| pages = 353–366| doi = 10.1111/j.1502-3931.1997.tb00481.x }}</ref><ref name=Ch12Metatherians>{{Cite book| author = [[Zofia Kielan-Jaworowska]], Richard L. Cifelli, Zhe-Xi Luo | url = https://books.google.com/books?id=qJGcX3X0EaMC | title = Mammals from the Age of Dinosaurs: origins, evolution, and structure | publisher = Columbia University Press | location = New York | year = 2004 | pages = 241–243 | chapter = Chapter 12: Metatherians | isbn = 978-0-231-11918-4 }}</ref>}} for which there is good evidence that it fed on vertebrates, including [[dinosaur]]s.  Though it is not entirely clear whether these animals primarily hunted live dinosaurs or scavenged dead ones, evidence for the former is present in fossilized remains showcasing the results of what was most likely a predation attempt by ''R. robustus'' directed at a specimen of the dinosaur ''[[Psittacosaurus|Psittacosaurus lujiatunensis]]''.<ref name=":0">{{Cite journal |last1=Han |first1=Gang |last2=Mallon |first2=Jordan C. |last3=Lussier |first3=Aaron J. |last4=Wu |first4=Xiao-Chun |last5=Mitchell |first5=Robert |last6=Li |first6=Ling-Ji |date=2023-07-18 |title=An extraordinary fossil captures the struggle for existence during the Mesozoic |journal=Scientific Reports |language=en |volume=13 |issue=1 |page=11221 |doi=10.1038/s41598-023-37545-8 |pmid=37464026 |issn=2045-2322|pmc=10354204 }}</ref>  ''R. giganticus'' is among the largest mammals known from the Mesozoic era, only surpassed by ''[[Patagomaia]]''.

== Classification and discovery ==
[[Image:Repenomamus BW.jpg|thumb|left|An ''R. robustus'' feeding on a ''Psittacosaurus'' hatchling.]]
The fossils were recovered from the [[Lagerstätten|lagerstätte]] of the [[Yixian Formation]] in the Liaoning province of China, which is renowned for its extraordinarily well-preserved fossils of [[feathered dinosaurs]]. They have been specifically dated to 125–123.2 [[million years ago]], during the [[Early Cretaceous]] period.

''Repenomamus'' is a [[genus]] of [[eutriconodont]]s, a group of early [[mammal]]s with no modern relatives. ''R. robustus'' was described by Li, Wang, Wang and Li in 2001, and ''R. giganticus'' was described by Hu, Meng, Wang and Li in 2005. The two known [[species]] are the sole members of the family Repenomamidae, which was also described in the same paper in 2001. It is sometimes alternatively listed as a member of the family [[Gobiconodontidae]]; although this assignment is controversial, a close relationship to this family is well-founded.

==Description==
[[File:Repenomamus robustus skeletal drawing.png|left|thumb|''R. robustus'' skeletal diagram.]]
[[File:Repenomamus giganticus skull.JPG|left|thumb|Fossil skull of ''R. giganticus'']]
Individuals of the known species in ''Repenomamus'' are some of [[largest prehistoric animals|the largest]] known [[Mesozoic]] mammals<ref>{{cite book
| url         = https://books.google.com/books?id=DUli1Mb8j7QC 
| title       = Evolution of Fossil Ecosystems. Second edition
| publisher   = Academic Press
| date        = Sep 19, 2012
| access-date  = 2022-08-25
| page        = 178
| author      = Paul Selden, John Nudds
| isbn = 978-0-12-404629-0
}}</ref><ref name=Ch12Metatherians/><ref name="Prothero">{{cite book
| url         = https://books.google.com/books?id=tWiYDwAAQBAJ&dq=repenomamus+largest&pg=PA33
| title       = The Princeton Field Guide to Prehistoric Mammals
| publisher   = Princeton University Press
| date        = November 15, 2016
| access-date  = 2022-08-25
| page        = 33
| author      = Donald R. Prothero
| isbn = 978-0-691-15682-8
}}</ref><ref name="Zachos">{{cite book
| url         = https://books.google.com/books?id=dQd2DwAAQBAJ&dq=repenomamus+largest&pg=PA224
| title       = Mammalian Evolution, Diversity and Systematics
| publisher   = De Gruyter
| date        = October 22, 2018
| access-date  = 2022-08-25
| page        = 224
| author      = Frank Zachos, Robert Asher
| isbn = 978-3-11-034155-3
}}</ref><ref>{{cite book
| url         = https://books.google.com/books?id=3bs0D5ix4VAC&dq=repenomamus+largest&pg=PA62
| title       = The Beginning of the Age of Mammals
| publisher   = Johns Hopkins University Press
| date        = 2006
| access-date  = 2022-08-25
| page        = 62
| author      = Kenneth D. Rose
| isbn = 978-0-8018-8472-6
}}</ref><ref>{{cite book
| url         = https://books.google.com/books?id=wuwtxuJoX6IC&dq=repenomamus+largest&pg=PA715
| title       = In Pursuit of Early Mammals
| publisher   = Indiana University Press
| date        = 2013
| access-date  = 2022-08-25
| page        = 115
| author      = Zofia Kielan-Jaworowska
| isbn = 978-0-253-00824-4
}}</ref> represented by reasonably complete fossils<ref name="Prothero"/><ref name="Zachos"/> (though ''[[Kollikodon]]'' and ''[[Patagomaia]]'' may be larger,<ref>Clemens et al., 2003</ref><ref>{{Cite journal|last1=Chimento |first1=N. R. |last2=Agnolín |first2=F. L. |last3=García-Marsà |first3=J. |last4=Manabe |first4=M. |last5=Tsuihiji |first5=T. |last6=Novas |first6=F. E. |year=2024 |title=A large therian mammal from the Late Cretaceous of South America |journal=Scientific Reports |volume=14 |at=2854 |doi=10.1038/s41598-024-53156-3 |doi-access=free |pmc=10838296 }}</ref> and ''[[Schowalteria]]'', ''[[Oxlestes]]'', ''[[Khuduklestes]]'' and ''[[Bubodens]]'' reached similar if not larger sizes<ref>{{cite journal | author = Fox R. C., Naylor B. G. | year = 2003 | title = A Late Cretaceous taeniodont (Eutheria, Mammalia) from Alberta, Canada | journal = Neues Jahrbuch für Geologie und Paläontologie | volume = 229 | issue = 3| pages = 393–420 | doi = 10.1127/njgpa/229/2003/393 }}</ref><ref>{{cite journal | author = Wilson R. W. | year = 1987 | title = Late Cretaceous (Fox Hills) multituberculates from the Red Owl local fauna of western South Dakota | journal = Dakoterra | volume = 3 | pages = 118–122 }}</ref>). Adults of ''R. robustus'' were the size of a [[Virginia opossum]]. It had body length without tail of {{convert|41.2|cm|abbr=on|sigfig=2}} for complete specimen with estimated skull length of {{convert|10.6|cm|abbr=on|sigfig=2}}, although there is more partial specimen that had {{convert|11.2|cm|abbr=on|sigfig=2}} skull. Estimated mass of ''R. robustus'' is {{convert|4|-|6|kg|abbr=on|sigfig=2}}. 

The known adult of ''R. giganticus'' was about 50% larger than ''R. robustus'', with a body length of {{convert|68.2|cm|abbr=on|sigfig=2}} and total length over {{convert|1|m|abbr=on|sigfig=2}} (skull reaching {{convert|16|cm|abbr=on|sigfig=2}},  trunk of {{convert|52.2|cm|abbr=on|sigfig=2}} and preserved tail {{convert|36.4|cm|abbr=on|sigfig=2}} in length) and an estimated mass of {{convert|12|-|14|kg|abbr=on|sigfig=2}}.<ref name="Hu et al 2005" /> These finds extend considerably the known body size range of Mesozoic mammals. In fact, ''Repenomamus'' was larger than several small sympatric dromaeosaurid dinosaurs like ''[[Graciliraptor]]''.<ref name="Hu et al 2005">{{cite journal|title=Large Mesozoic mammals fed on young dinosaurs|journal=Nature|date=2005|volume=433|pages=149–152|author=Hu|doi=10.1038/nature03102|pmid=15650737|issue=7022|bibcode=2005Natur.433..149H|s2cid=2306428|url=http://doc.rero.ch/record/15291/files/PAL_E2590.pdf |display-authors=etal}}[ Supplementary Information]</ref><ref name="Prothero" /> Features of its shoulder and legs bones indicate a sprawling posture as in most of small to medium sized living [[theria]]n mammals, with [[plantigrade]] feet. Unlike therian mammals, ''Repenomamus'' had a proportionally longer body with shorter limbs.

The [[Dentition|dental formula]] was originally interpreted as {{DentalFormula|upper=3.1.2.4|lower=2.1.2.5}}, though a more recent study indicates instead that it was {{DentalFormula|upper=3.1.1.5|lower=2.1.2.5}}.<ref>Alexey Lopatin, Alexander Averianov, Gobiconodon (Mammalia) from the Early Cretaceous of Mongolia and Revision of Gobiconodontidae, First online: 12 July 2014</ref>

==Paleobiology==
[[File:Repenomamus robustus-Paleozoological Museum of China.jpg|alt=|thumb|304x304px|''R. robustus'' specimen with ''Psittacosaurus'' remains in its stomach, [[Paleozoological Museum of China]].]]
Features of the teeth and jaw suggest that ''Repenomamus'' were [[carnivore|carnivorous]] and a specimen of ''R. robustus'' discovered with the fragmentary skeleton of a juvenile ''[[Psittacosaurus]]'' preserved in its [[stomach]] represents the second direct evidence that at least some Mesozoic mammals were carnivorous and fed on other vertebrates, including dinosaurs;<ref name="Hu et al 2005"/> a recorded attack on an ''[[Archaeornithoides]]'' by a ''[[Deltatheridium]]'' predates its description.<ref>{{cite journal | doi = 10.2475/ajs.293.A.235 | url = http://earth.geology.yale.edu/~ajs/1993/11.1993.08Elzanowski.pdf | title = Skull of Archaeornithoides from the Upper Cretaceous of Mongolia | year = 1993 | last1 = Elzanowski | first1 = A. | last2 = Wellnhofer | first2 = P. | journal = American Journal of Science | volume = 293 | pages = 235–252 | bibcode = 1993AmJS..293..235E }}</ref> 

More evidence suggesting ''Repenomamus'' was suited to a predatory lifestyle was later revealed when a specimen of ''R. robustus'' was uncovered alongside an adult ''[[Psittacosaurus]]''. The intertwined nature of the fossil, similar to the [[Fighting Dinosaurs]] fossil of Mongolia, was likely a byproduct of an altercation between the two animals in which the mammal was most likely the instigator of an ongoing predation attempt. This was posited on the basis that the ''Repenomamus'' involved was noted to have been latching on to the ''Psittacosaurus'' with its arms and legs while biting the dinosaur.<ref name=":0" /> Speciations towards carnivory are known in [[eutriconodonts]] as a whole, and similarly large sized species like ''[[Gobiconodon]]'', ''[[Jugulator (mammal)|Jugulator]]'' and even ''[[Triconodon]]'' itself<ref>{{Cite web | url=https://www.britannica.com/animal/Triconodon |title = Triconodon &#124; fossil mammal genus}}</ref> are thought to have tackled proportionally large prey as well; evidence of scavenging is even assigned to the former.<ref name="Ch12Metatherians" />

Like most other non-[[placental]] mammals, ''Repenomamus'' had [[epipubic bone]]s, implying that it gave birth to undeveloped young like modern [[marsupials]], or laid eggs like modern [[monotremes]].<ref name="Hu et al 2005"/>

{{Multiple image
| image1            = Psittacosaurus lujiatunensis-Repenomamus robustus pair (WZSSM VF000011) locked in mortal combat.webp
| image2            = Psittacosaurus and Repenomamus life restoration - Han et al 2023.png
| footer            = ''R. robustus'', locked in combat with ''Psittacosaurus lujiatunensis''.
| total_width       = 700
| align             = center
}}

==See also==
{{Portal|Paleontology}}
* [[Mammaliaformes]]
* [[Cynodont]]s
* ''[[Cynognathus]]''
* [[Evolution of mammals]]

==References==
{{Reflist}}

== External links ==

* "[http://www.nature.com/news/2005/050110/full/050110-11.html Prehistoric badger had dinosaurs for breakfast]". Michael Hopkin. ''Nature.com''. January 12, 2005.
* "[http://news.bbc.co.uk/2/hi/science/nature/4165973.stm Fierce mammal ate dinos for lunch]". ''BBC News''. January 12, 2005.
{{Mammaliaformes|T.}}
{{Taxonbar|from=Q131960}}

[[Category:Cretaceous mammals]]
[[Category:Gobiconodontidae]]
[[Category:Early Cretaceous mammals of Asia]]
[[Category:Fossil taxa described in 2000]]
[[Category:Yixian fauna]]
[[Category:Taxa named by Jinling Li]]
[[Category:Taxa named by Wang Yuan]]
[[Category:Taxa named by Yuanqing Wang]]
[[Category:Taxa named by Chuankui Li]]
[[Category:Prehistoric mammal genera]]