Editing Multituberculata (section)

==Evolution==

Multituberculates first appear in the fossil record during the [[Jurassic]] period, and then survived and even dominated for over one hundred million years, longer than any other order of [[mammaliforms]], including placental mammals. The earliest known multituberculates are from the [[Middle Jurassic]] ([[Bathonian]] ~166-168 million years ago) of England and Russia, including ''[[Hahnotherium]]'' ''and [[Kermackodon]]'' from the [[Forest Marble Formation]] of England, and ''[[Tashtykia]]'' and ''[[Tagaria (mammal)|Tagaria]]'' from the [[Itat Formation]] of Russia. These forms are only known from isolated teeth, which bear close similarity to those of [[Euharamiyida|euharamyidans]], which they are suspected to be closely related to.<ref name=":1">{{cite journal |last1=Averianov |first1=Alexander O. |last2=Martin |first2=Thomas |last3=Lopatin |first3=Alexey V. |last4=Schultz |first4=Julia A. |last5=Schellhorn |first5=Rico |last6=Krasnolutskii |first6=Sergei |last7=Skutschas |first7=Pavel |last8=Ivantsov |first8=Stepan |title=Multituberculate mammals from the Middle Jurassic of Western Siberia, Russia, and the origin of Multituberculata |journal=Papers in Palaeontology |date=May 2021 |volume=7 |issue=2 |pages=769–787 |doi=10.1002/spp2.1317 |s2cid=219067218 |issn=2056-2799 |url=https://zenodo.org/record/3877503 }}</ref> During the Late Jurassic and Early Cretaceous, primitive multituberculates, collectively grouped into the [[Paraphyly|paraphyletic]] "[[Plagiaulacida]]", were abundant and widespread across [[Laurasia]] (including Europe, Asia and North America). During the [[Aptian]] stage of the Early Cretaceous, the advanced subgroup [[Cimolodonta]] appeared in North America, characterised by a reduced number of lower premolars, with a blade-like lower fourth premolar. By the early Late Cretaceous ([[Cenomanian]]) Cimolodonta had replaced all other multituberculate lineages.<ref>{{Cite journal|last1=Weaver|first1=Lucas N.|last2=Wilson|first2=Gregory P.|last3=Krumenacker|first3=L. J.|last4=Mclaughlin|first4=Kayla|last5=Moore|first5=Jason R.|last6=Varricchio|first6=David J.|date=2019-03-04|title=New multituberculate mammals from the mid-Cretaceous (lower Cenomanian) Wayan Formation of southeastern Idaho and implications for the early evolution of Cimolodonta|url=https://www.tandfonline.com/doi/full/10.1080/02724634.2019.1604532|journal=Journal of Vertebrate Paleontology|language=en|volume=39|issue=2|pages=e1604532|doi=10.1080/02724634.2019.1604532|bibcode=2019JVPal..39E4532W |s2cid=196655261 |issn=0272-4634|url-access=subscription}}</ref>

During the Late Cretaceous, multituberculates experienced an [[adaptive radiation]], corresponding with a shift towards herbivory.<ref>{{Cite journal|last1=Wilson|first1=Gregory P.|last2=Evans|first2=Alistair R.|last3=Corfe|first3=Ian J.|last4=Smits|first4=Peter D.|last5=Fortelius|first5=Mikael|last6=Jernvall|first6=Jukka|date=March 2012|title=Adaptive radiation of multituberculate mammals before the extinction of dinosaurs|url=https://www.nature.com/articles/nature10880|journal=Nature|language=en|volume=483|issue=7390|pages=457–460|doi=10.1038/nature10880|pmid=22419156 |bibcode=2012Natur.483..457W |s2cid=4419772 |issn=1476-4687|url-access=subscription}}</ref> Multituberculates reached their peak diversity during the early [[Paleocene]], shortly after the [[Cretaceous–Paleogene extinction event]], but declined from the mid Paleocene onwards, likely due to competition with placental mammals such as [[rodent]]s and [[ungulate]]s, the group finally became extinct in the Late [[Eocene]].<ref>{{Cite journal|last1=Adams|first1=Neil F.|last2=Rayfield|first2=Emily J.|last3=Cox|first3=Philip G.|last4=Cobb|first4=Samuel N.|last5=Corfe|first5=Ian J.|date=March 2019|title=Functional tests of the competitive exclusion hypothesis for multituberculate extinction|journal=Royal Society Open Science|language=en|volume=6|issue=3|pages=181536|doi=10.1098/rsos.181536|issn=2054-5703|pmc=6458384|pmid=31032010|bibcode=2019RSOS....681536A }}</ref><ref name="Brocklehurst et al 2021">{{cite journal|last1=Brocklehurst|first1=Neil|last2=Panciroli|first2=Elsa|last3=Benevento|first3=Gemma Louise|last4=Benson|first4=Roger B. J.|date=July 2021|title=Mammaliaform extinctions as a driver of the morphological radiation of Cenozoic mammals|journal=Current Biology|volume=31|issue=13|pages=2955–2963.e4|doi=10.1016/j.cub.2021.04.044|pmid=34004143|s2cid=234782605|url=https://ora.ox.ac.uk/objects/uuid:bda82407-db76-4c15-b061-ceb9ae271dd5 |doi-access=free}}</ref>

There are some isolated records of multituberculates from the Southern Hemisphere, including the cimolodontan ''[[Corriebaatar]]'' from the Early Cretaceous of Australia,<ref name=":0">{{Cite journal |last1=Rich |first1=Thomas |last2=Trusler |first2=Peter |last3=Kool |first3=Lesley |last4=White |first4=Matt A. |last5=Bevitt |first5=Joseph |last6=Morton |first6=Steven |last7=Vickers−Rich |first7=Patricia |date=2022 |title=Second specimen of Corriebaatar marywaltersae from the Lower Cretaceous of Australia confirms its multituberculate affinities |journal=Acta Palaeontologica Polonica |volume=67 |doi=10.4202/app.00924.2021 |s2cid=247905998 |issn=0567-7920|doi-access=free }}</ref> and fragmentary remains from the Late Cretaceous [[Maevarano Formation]] of Madagascar.<ref>{{Cite journal |last1=Krause |first1=David W. |last2=Hoffmann |first2=Simone |last3=Werning |first3=Sarah |date=December 2017 |title=First postcranial remains of Multituberculata (Allotheria, Mammalia) from Gondwana |journal=Cretaceous Research |language=en |volume=80 |pages=91–100 |doi=10.1016/j.cretres.2017.08.009|bibcode=2017CrRes..80...91K |doi-access=free }}</ref> The family [[Ferugliotheriidae]] from the Late Cretaceous of South America, traditionally considered gondwanatherians, may actually be cimolodontan multituberculates.<ref name=":0" />

During the Late Cretaceous and Paleocene the multituberculates [[Evolutionary radiation|radiated]] into a wide variety of [[morphotype]]s, including the squirrel-like arboreal [[Ptilodontidae|ptilodonts]]. The peculiar shape of their last lower [[premolar]] is their most outstanding feature. These teeth were larger and more elongated than the other cheek-teeth and had an [[Occlusion (dentistry)|occlusive]] surface forming a serrated slicing blade. Though it can be assumed that this was used for crushing seeds and nuts, it is believed that most small multituberculates also supplemented their diet with insects, worms, and fruits.<ref name="Agusti-3" /> Tooth marks attributed to multituberculates are known on ''[[Champsosaurus]]'' fossils, indicating that at least some of these mammals were [[scavenger]]s.<ref>{{cite journal | doi = 10.1111/j.1475-4983.2010.00957.x | volume=53 | title=Mammalian tooth marks on the bones of dinosaurs and other Late Cretaceous vertebrates | journal=Palaeontology | pages=703–709 | last1 = Longrich | first1 = Nicholas R. | last2 = Ryan | first2 = Michael J.| year=2010 | issue=4 | bibcode=2010Palgy..53..703L | doi-access = free }}</ref> A ptilodont that thrived in North America was ''[[Ptilodus]]''. Thanks to the well-preserved ''Ptilodus'' specimens found in the [[Bighorn Basin]], [[Wyoming]], we know that these multituberculates were able to [[Anatomical terms of motion|abduct and adduct]] their [[hallux|big toes]], and thus that their foot mobility was similar to that of modern squirrels, which descend trees head first.<ref name="Agusti-3" />

[[File:Catopsbaatar.jpg|thumb|left|Restoration of ''[[Catopsbaatar]]'']]

Another group of multituberculates, the [[Taeniolabidoidea|taeniolabids]], were heavier and more massively built, indicating that they lived a fully terrestrial life. The largest specimens weighed probably as much as {{convert|22|kg|abbr=on}}, making them comparable in size to large rodents like the modern beaver.<ref>Krause et al 2021</ref><ref>Wilson et al 2012</ref>