Eutheria

Further information: Evolution of mammals
For the genus of beetles, see List of Cassidinae genera.

Eutheria
Temporal range: Early Cretaceous–Recent
Skeleton of Microtherulum, a basal eutherian from the Early Cretaceous of China
Northern treeshrew (Tupaia belangeri), a placental eutherian from Southeast Asia
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Subclass: Theria
Clade: Eutheria
Gill, 1872
Subgroups

see text.

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] though epipubic bones are present in many primitive eutherians.[2] Eutheria was named in 1872 by Theodore Gill; in 1880, Thomas Henry Huxley defined it to encompass a more broadly defined group than Placentalia.[3]

The earliest unambiguous eutherians are known from the Early Cretaceous Yixian Formation of China, dating around 120 million years ago.[4] Two tribosphenic mammals, Durlstodon and Durlstotherium from the Berriasian age (~145-140 million years ago) of the Early Cretaceous in southern England have also been suggested to represent early eutherians.[5][6] Another possible eutherian species Juramaia sinensis has been dated at 161 million years ago from the early Late Jurassic (Oxfordian) of China.[7] However some authors have considered Juramaia as a stem therian instead,[5][6] and some sources have doubted the dating of the specimen.[8]

  1. ^ Reilly, Stephen M.; White, Thomas D. (2003-01-17). "Hypaxial Motor Patterns and the Function of Epipubic Bones in Primitive Mammals". Science. 299 (5605): 400–402. Bibcode:2003Sci...299..400R. doi:10.1126/science.1074905. ISSN 0036-8075. PMID 12532019.
  2. ^ Guilhon, Gabby; Braga, Caryne; Milne, Nick; Cerqueira, Rui (November 2021). "Musculoskeletal anatomy and nomenclature of the mammalian epipubic bones". Journal of Anatomy. 239 (5): 1096–1103. doi:10.1111/joa.13489. ISSN 0021-8782. PMC 8546510. PMID 34195985.
  3. ^ Archibald, J David. Eutheria (Placental Mammals) (PDF). San Diego, California: San Diego State University.
  4. ^ Beck, Robin M. D. (2023), Cáceres, Nilton C.; Dickman, Christopher R. (eds.), "Diversity and Phylogeny of Marsupials and Their Stem Relatives (Metatheria)", American and Australasian Marsupials, Cham: Springer International Publishing, pp. 23–88, doi:10.1007/978-3-031-08419-5_35, ISBN 978-3-031-08418-8, retrieved 2024-08-04
  5. ^ a b Sweetman, S.C.; Smith, G.; Martill, D.M. (2017). "Highly derived eutherian mammals from the earliest Cretaceous of southern Britain". Acta Palaeontologica Polonica. 62 (4): 657–665. doi:10.4202/app.00408.2017.
  6. ^ a b Martin, T. A.; Averianov, A. O.; Schultz, J. A.; Schwermann, A. H. (2023). "A stem therian mammal from the Lower Cretaceous of Germany". Journal of Vertebrate Paleontology. 42 (6). e2224848. doi:10.1080/02724634.2023.2224848. S2CID 260265765.
  7. ^ Luo, Z.; C. Yuan; Q. Meng; Q. Ji (2011). "A Jurassic eutherian mammal and divergence of marsupials and placentals". Nature. 476 (7361): 42–45. Bibcode:2011Natur.476..442L. doi:10.1038/nature10291. PMID 21866158.
  8. ^ King, Benedict; Beck, Robin M. D. (2020-06-10). "Tip dating supports novel resolutions of controversial relationships among early mammals". Proceedings of the Royal Society B: Biological Sciences. 287 (1928): 20200943. doi:10.1098/rspb.2020.0943. ISSN 0962-8452. PMC 7341916. PMID 32517606.