Eutheria (from Greek εὐ-, eú- 'good, right' and θηρίον, thēríon 'beast';
lit.'true beasts'), also called Pan-Placentalia, is the
clade consisting of
placental mammals and all
therian mammals that are more closely related to placentals than to
marsupials.
Eutherians are distinguished from noneutherians by various
phenotypic traits of the feet, ankles, jaws and teeth. All extant eutherians lack
epipubic bones, which are present in all other living mammals (marsupials and
monotremes). This allows for expansion of the abdomen during pregnancy.[1] However epipubic bones are present in some primitive eutherians.[2]
The oldest-known eutherian species is Juramaia sinensis, dated at 161 million years ago from the early
Late Jurassic (
Oxfordian) of China.[3] However, this early dating has been questioned, and Juramaia may originate from Early Cretaceous instead, which would make it contemporaneous to several other known eutherians.[4]
Eutheria was named in 1872 by
Theodore Gill; in 1880,
Thomas Henry Huxley defined it to encompass a more broadly defined group than Placentalia.[5]
Characteristics
Distinguishing features are:
an enlarged
malleolus ("little hammer") at the bottom of the
tibia, the larger of the two shin bones[6]
the
joint between the first
metatarsal bone and the entocuneiform bone (the innermost of the three
cuneiform bones) in the foot is offset farther back than the joint between the second metatarsal and middle cuneiform bones—in metatherians these joints are level with each other[6]
Some older systems contained an order called
Cimolesta (sensu lato), which contains the above taxa Cimolestidae, Taeniodonta and Didymoconidae, but also (all or some of) the taxa †
Ptolemaiidae, †
Palaeoryctidae, †
Wyolestidae, †
Pantolesta (probably inclusive of the family †
Horolodectidae), †
Tillodontia, †
Apatotheria, †
Pantodonta,
Pholidota and †
Palaeanodonta. Those additional taxa (all of which are usually considered members of Placentalia sensu stricto today) were thus also placed among basal Eutheria in such older systems and were placed next to Cimolestidae.
Some systems also included the †
Creodonta and/or †
Dinocerata as basal Eutherians.
Some authors classify the taxa, which are at the end of the above system of basal Eutheria, as part of Placentalia sensu stricto. More specifically, depending on the author, this applies to the taxa of the above system that are placed from (and inclusive of) Leptictida or Asioryctitheria or Adapisoriculidae down to (and inclusive of) Oxyprimus.
Evolutionary history
Eutheria contains several
extinctgenera as well as larger groups, many with complicated
taxonomic histories still not fully understood. Members of the
Adapisoriculidae,
Cimolesta and
Leptictida have been previously placed within the outdated placental group
Insectivora, while
Zhelestids have been considered primitive
ungulates.[29] However, more recent studies have suggested these enigmatic taxa represent
stem group eutherians, more basal to Placentalia.[30][31]
The weakly favoured cladogram favours Boreoeutheria as a basal eutherian clade as sister to the Atlantogenata.[32][33][34]
Many non-placental eutherians are thought to have been
insectivores, as is the case with many primitive mammals.[37] However the
zhelestids are thought to have been herbivorous.[36]
^Zachos, F.; Asher, R. (2018). Mammalian Evolution, Diversity and Systematics. De Gruyter. pp. 271–339, mainly p. 277.
ISBN978-3-11-034155-3.
^Benton, Michael J. (2014-10-20). Vertebrate Palaeontology. Chichester: John Wiley & Sons. pp. 443–444.
ISBN978-1-118-40755-4.
^Zima, Jan; Macholán, Miloš (2021). Systém a fylogeneze savců (in Czech). pp. 130–149.
ISBN978-80-200-3215-7.
^Lopatin, Alexey & Averianov, Alexander. (2018). Earliest Placentals: at the Dawn of Big Time / Древнейшие плацентарные: начало истории успеха. Priroda. 34-40.
[1]
^Velazco, P.M., Buczek, A.J., Hoffman, E., Hoffman, D.K., O’Leary, M.A. and Novacek, M.J. (2022), Combined data analysis of fossil and living mammals: a Paleogene sister taxon of Placentalia and the antiquity of Marsupialia. Cladistics, 38: 359-373.
https://doi.org/10.1111/cla.12499
^Bi, Shundong; Zheng, Xiaoting; Wang, Xiaoli; Cignetti, Natalie E.; Yang, Shiling; Wible, John R. (2018). "An Early Cretaceous eutherian and the placental–marsupial dichotomy". Nature. 558 (7710): 390–395. Bibcode:2018Natur.558..390B. doi:10.1038/s41586-018-0210-3. ISSN 1476-4687. PMID 29899454. S2CID 91737831
^Wang, Hai-Bing; Hoffmann, Simone; Wang, Dian-Can; Wang, Yuan-Qing (7 February 2022). "A new mammal from the Lower Cretaceous Jehol Biota and implications for eutherian evolution". Philosophical Transactions of the Royal Society B. 377 (1847). doi:10.1098/rstb.2021.0042. PMC 8819371. PMID 35125007.
^Rook, Deborah L.; Hunter, John P. (2013). "Rooting Around the Eutherian Family Tree: the Origin and Relations of the Taeniodonta". Journal of Mammalian Evolution. 21: 1–17.
doi:
10.1007/s10914-013-9230-9.
^Maureen A. O'Leary et al. Placentals K-Pg Radiation of−The Placental Mammal Ancestor and the Post-K-Pg Radiation of−Placentals. Science 339, 662 (2013)
^Rose, Kenneth D. (2006-09-26). The Beginning of the Age of Mammals. Baltimore (Md.): JHU Press.
ISBN0-8018-8472-1. ch. 6 and ch. 7
^Halliday, T.J.D., Upchurch, P. and Goswami, A. (2017), Resolving the relationships of Paleocene placental mammals. Biol Rev, 92: 521-550.
https://doi.org/10.1111/brv.12242
^Averianov, Alexander. (2012). A new eutherian mammal from the Late Cretaceous of Kazakhstan. Acta Palaeontologica Polonica. 59. 10.4202/app.2011.0143.
^Cifelli, Richard & Davis, Brian. (2015). Tribosphenic Mammals from the Lower Cretaceous Cloverly Formation of Montana and Wyoming. Journal of Vertebrate Paleontology. 35. e920848. 10.1080/02724634.2014.920848.
^KIELAN-JAWOROWSKA, Z. : Evolution of the therian mammals in the Late Cretaceous of Asia. PART I. DELTATHERIDIIDAE (plates XXVIII-XXXV). 1984. p. 123, 124
[2]
^Wang, Y-Q & Kusuhashi, Nao & Jin, Xun & Chuan-kui, LI & Takeshi, SETOGUCHI & Chun-Ling, GAO & Jin-Yuan, LIU & Palasiatica, Vertebrata. (2018). Reappraisal of Endotherium niinomii Shikama, 1947, a eutherian mammal from the Lower Cretaceous Fuxin Formation, Fuxin-Jinzhou Basin, Liaoning, China.
^Wilson Mantilla, Gregory P.; Renne, Paul R.; Samant, Bandana; Mohabey, Dhananjay M.; Dhobale, Anup; Tholt, Andrew J.; Tobin, Thomas S.; Widdowson, Mike; Anantharaman, S.; Dassarma, Dilip Chandra; Wilson Mantilla, Jeffrey A. (2022). "New mammals from the Naskal intertrappean site and the age of India's earliest eutherians". Palaeogeography, Palaeoclimatology, Palaeoecology. Elsevier BV. 591.
doi:
10.1016/j.palaeo.2022.110857.
ISSN0031-0182.
^Craig S Scott, Horolodectidae: a new family of unusual eutherians (Mammalia: Theria) from the Palaeocene of Alberta, Canada, Zoological Journal of the Linnean Society, Volume 185, Issue 2, February 2019, Pages 431–458,
https://doi.org/10.1093/zoolinnean/zly040
^Kynigopoulou, Zoi. Phylogeny, evolution, and anatomy of Taeniodonta (Mammalia: Eutheria) and implications for the mammalian evolution after the Cretaceous-Palaeogene mass extinction. 2023
[3]
^Rose, Kenneth D. (2006). The beginning of the age of mammals. Baltimore: Johns Hopkins University Press.
ISBN9780801892219.
^Wible, J. R.; Rougier, G. W.; Novacek, M. J.; Asher, R. J. (2007). "Cretaceous eutherians and Laurasian origin for placental mammals near the K/T boundary". Nature. 447 (7147): 1003–1006.
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PMID17581585.
^
abGheerbrant E. & Teodori D. 2021. — An enigmatic specialized new eutherian mammal from the Late Cretaceous of Western Europe (Northern Pyrenees), in Folie A., Buffetaut E., Bardet N., Houssaye A., Gheerbrant E. & Laurin M. (eds), Palaeobiology and palaeobiogeography of amphibians and reptiles: An homage to Jean-Claude Rage. Comptes Rendus Palevol 20 (13): 207-223.
https://doi.org/10.5852/cr-palevol2021v20a13