Scrotifera Explained

Scrotifera ("scrotum bearers") is a clade of placental mammals that groups together grandorder Ferungulata, Chiroptera (bats), other extinct members and their common ancestors. The clade Scrotifera is a sister group to the order Eulipotyphla (true insectivores) based on evidence from molecular phylogenetics, and together they make superorder Laurasiatheria. The last common ancestor of Scrotifera is supposed to have diversified ca. 73.1^[1] to 85.5 million years ago.

Etymology

Peter Waddell, then of the Institute of Statistical Mathematics, explains the etymology of the clade's name as follows:

The name comes from the word scrotum, a pouch in which the testes permanently reside in the adult male. All members of the group have a postpenile scrotum, often prominently displayed, except for some aquatic forms and pangolin (which has the testes just below the skin). It appears to be an ancestral character for this group, yet other orders generally lack this as an ancestral feature, with the probable exception of Primates.

Classification and phylogeny

History of phylogeny

In 2006, the clade Pegasoferae (a clade of mammals that includes orders Chiroptera, Carnivora, Perissodactyla and Pholidota) was proposed as part of the clade Scrotifera and a sister group to the order Artiodactyla, based on genomic research in molecular systematics.^[2] The monophyly of the group is not well supported, and recent studies have indicated that this clade is not a natural grouping.^{[3] [4]}

According to a 2022 study, two extinct species (Eosoricodon terrigena and "Wyonycteris" microtis) were identified as outside of the family Nyctitheriidae and more closely related mammals to bats.^[5] In another 2022 study, the extinct genus Acmeodon was recognized as not a member of the extinct order Cimolesta but a basal laurasiatherian mammal in the clade Scrotifera.^{[6] [7]}

Taxonomy

See also

• Mammal classification
• Laurasiatheria

Notes and References

1. dos Reis . Mario . Inoue . Jun . Hasegawa . Masami . Asher . Robert J. . Donoghue . Philip C. J. . Yang . Ziheng . 2012-09-07 . Phylogenomic datasets provide both precision and accuracy in estimating the timescale of placental mammal phylogeny . Proceedings of the Royal Society B: Biological Sciences . en . 279 . 1742 . 3491–3500 . 10.1098/rspb.2012.0683 . 0962-8452 . 3396900 . 22628470.
2. Nishihara . H. . Hasegawa . M. . Okada . N. . Pegasoferae, an unexpected mammalian clade revealed by tracking ancient retroposon insertions . . 103 . 26 . 9929–9934 . 2006 . 10.1073/pnas.0603797103 . 16785431 . 1479866. free .
3. Zhou . Xuming . Xu . Shixia . Xu . Junxiao . Chen . Bingyao . Zhou . Kaiya . Yang . Guang . 2012-01-01 . Phylogenomic Analysis Resolves the Interordinal Relationships and Rapid Diversification of the Laurasiatherian Mammals . Systematic Biology . en . 61 . 1 . 150–64 . 10.1093/sysbio/syr089 . 1063-5157 . 3243735 . 21900649.
4. Tsagkogeorga . G. . Parker . J. . Stupka . E. . Cotton . J. A. . Rossiter . S. J. . 2013 . Phylogenomic analyses elucidate the evolutionary relationships of bats (Chiroptera) . Current Biology . 23 . 2262–2267 . 24184098 . 22 . 10.1016/j.cub.2013.09.014 . free.
5. Matthew F. Jones, Nancy Simmons, K. Christopher Beard (2022.) "Relationship of nyctitheres (Mammalia, Nyctitheriidae) to bats and other laurasiatherians", in "The Society of Vertebrate Paleontology 82nd annual meeting"
6. Bertrand . O. C. . Shelley . S. L. . Williamson . T. E. . Wible . J. R. . Chester . S. G. B. . Flynn . J. J. . Holbrook . L. T. . Lyson . T. R. . Meng . J. . Miller . I. M. . Püschel . H. P. . Smith . T. . Spaulding . M. . Tseng . Z. J. . Brusatte . S. L. . 2022 . Brawn before brains in placental mammals after the end-Cretaceous extinction . Science . 376 . 6588 . 80–85 . 10.1126/science.abl5584 . 2022Sci...376...80B . 20.500.11820/d7fb8c6e-886e-4c1d-9977-0cd6406fda20 . free .
7. Bertrand . O. C. . Jiménez Lao . M. . Shelley . S. L. . Wible . J. R. . Williamson . T. E. . Meng . J. . Brusatte . S. L. . 2023 . The virtual brain endocast of Trogosus (Mammalia, Tillodontia) and its relevance in understanding the extinction of archaic placental mammals . Journal of Anatomy . 10.1111/joa.13951 . 37720992 . 262047180 .