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Scrotifera

Scrotifera
Temporal range: 66.3–0 Ma[1] Late Cretaceous to present
Representatives of the living orders of scrotiferans, from top to right: tiger (Carnivora), Indian pangolin (Pholidota), red deer (Artiodactyla), white rhino (Perissodactyla) and Lyle's flying fox (Chiroptera).
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Infraclass: Placentalia
Superorder: Laurasiatheria
Clade: Scrotifera
Waddell et al., 1999[2]
Major subgroups
For other groups and classification history, see text
Synonyms
  • Variamana (Springer, 2005)[3]

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,[2] and together they make up the superorder Laurasiatheria. The last common ancestor of Scrotifera is supposed to have diversified ca. 73.1[4] to 85.5[5] million years ago.

Etymology

The name Scrotifera, coined by Peter Waddell of the Institute of Statistical Mathematics, comes "from the word scrotum, a pouch in which the testes permanently reside in the adult male". It was chosen due to the presence of a postpenile scrotum in all members of Scrotifera, with the exception of some aquatic forms and pangolins.[2]

Description

Scrotifera is an evolutionary lineage, or clade, of placental mammals that includes ungulates, bats, carnivorans, and pangolins, as well as their common ancestors.[6] It was discovered through phylogenetic analyses and is one of the well-established mammalian clades, recovered by practically all comprehensive analyses.[7]

The common ancestor of Scrotifera might have been similar to Phenacodus, an early ungulate, in terms of body dimensions and life history (precociality in particular).[8]

Several characteristics likely present in the common ancestor of scrotiferans have been reconstructed based on the biological traits of its modern descendants. For example, this ancestor was probably a diurnal animal, as inferred from the positive selection of phototransduction genes associated with bright-light vision. After the divergence between the major scrotiferan groups, carnivorans and ungulates generally entered an evolutionary arms race of opposite daily activity patterns (as nocturnal predators and diurnal herbivores, respectively), while bats and pangolins became entirely nocturnal.[6]

In addition, reconstructions of the embryonic development of scrotiferans show that all organs develop considerably earlier in comparison to other mammals such as rodents. Like most of its descendants, the scrotiferan ancestor was precocial (i.e., born with relative maturity and independence), while certain descendants such as the carnivores then became more altricial (requiring significant parental care).[8]

At least two anatomical features are known to have been present in the scrotiferan ancestor. One feature, after which the group is named, is the postpenile scrotum, a pouch in the adult male that permanently contains the testes, often prominently displayed; other mammal orders generally lack this trait, and among scrotiferans, pangolins and aquatic forms (like cetaceans) secondarily reduced it.[2] Another is a well-developed entotympanic, an ear bone, although it was secondarily lost in even-toed ungulates.[9] Otherwise, due to the rapid radiation of placental mammals, the morphology of early scrotiferans was probably very similar to that of early members of the closely related eulipotyphlans and euarchontoglires. Morphological evolution is predicted to have occurred very slowly on those lineages compared to the molecular (genetic) evolution, and only accelerated with the divergence of the different orders.[10]

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.[11] The monophyly of the group is not well supported, and recent studies have indicated that this clade is not a natural grouping.[5][12]

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.[13] 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.[14][15]

Taxonomy

Former classification (Nishihara, 2006): Current classification:

See also

References

  1. ^ Archibald, J. David; Zhang, Yue; Harper, Tony; Cifelli, Richard L. (6 May 2011). "Protungulatum, confirmed Cretaceous occurrence of an otherwise Paleocene eutherian (placental?) mammal" (PDF). Journal of Mammalian Evolution. 18 (3): 153–161. doi:10.1007/s10914-011-9162-1. S2CID 16724836. Archived from the original (PDF) on 3 March 2016. Retrieved 28 April 2013.
  2. ^ a b c d Waddell, Peter J.; Cao, Ying; Hauf, Jöerg; Hasegawa, Masami (1 March 1999). Olmstead, R. (ed.). "Using Novel Phylogenetic Methods to Evaluate Mammalian mtDNA, Including Amino Acid-Invariant Sites-LogDet plus Site Stripping, to Detect Internal Conflicts in the Data, with Special Reference to the Positions of Hedgehog, Armadillo, and Elephant". Systematic Biology. 48 (1): 31–53. doi:10.1080/106351599260427. ISSN 1076-836X. PMID 12078643.
  3. ^ Springer M. S., Murphy W. J., Eizirik E., O'Brien S. J. In: "Placental Mammals: Origins and Relationships of the Major Clades." Rose K. D., Archibald J., editor. Baltimore: Johns Hopkins; (2005.) "Molecular evidence for major placental clades"; pp. 37–49
  4. ^ dos Reis, Mario; Inoue, Jun; Hasegawa, Masami; Asher, Robert J.; Donoghue, Philip C. J.; Yang, Ziheng (7 September 2012). "Phylogenomic datasets provide both precision and accuracy in estimating the timescale of placental mammal phylogeny". Proceedings of the Royal Society B: Biological Sciences. 279 (1742): 3491–3500. doi:10.1098/rspb.2012.0683. ISSN 0962-8452. PMC 3396900. PMID 22628470.
  5. ^ a b Zhou, Xuming; Xu, Shixia; Xu, Junxiao; Chen, Bingyao; Zhou, Kaiya; Yang, Guang (1 January 2012). "Phylogenomic Analysis Resolves the Interordinal Relationships and Rapid Diversification of the Laurasiatherian Mammals". Systematic Biology. 61 (1): 150–64. doi:10.1093/sysbio/syr089. ISSN 1063-5157. PMC 3243735. PMID 21900649.
  6. ^ a b Wu, Yonghua; Wang, Haifeng; Wang, Haitao; Feng, Jiang (29 January 2018). "Arms race of temporal partitioning between carnivorous and herbivorous mammals". Scientific Reports. 8 (1) 1713. doi:10.1038/s41598-018-20098-6. ISSN 2045-2322. PMC 5789060. PMID 29379083.
  7. ^ Zachos, Frank E. (2020). "Mammalian Phylogenetics: A Short Overview of Recent Advances". In Hackländer, Klaus; Zachos, Frank E. (eds.). Mammals of Europe - Past, Present, and Future. Cham: Springer. p. 31–48. doi:10.1007/978-3-030-00281-7_6. ISBN 978-3-030-00280-0.
  8. ^ a b Schlindwein, Xenia; Werneburg, Ingmar (2022). "Comparative embryogenesis in ungulate domesticated species". Journal of Experimental Zoology Part B: Molecular and Developmental Evolution. 338 (8). doi:10.1002/jez.b.23172. ISSN 1552-5007.
  9. ^ Maier, Wolfgang (2013). "The entotympanic in late fetal artiodactyla (Mammalia)". Journal of Morphology. 274 (8): 926–939. doi:10.1002/jmor.20149. ISSN 0362-2525.
  10. ^ Halliday, Thomas J. D.; dos Reis, Mario; Tamuri, Asif U.; Ferguson-Gow, Henry; Yang, Ziheng; Goswami, Anjali (13 March 2019). "Rapid morphological evolution in placental mammals post-dates the origin of the crown group". Proceedings of the Royal Society B: Biological Sciences. 286 (1898) 20182418. doi:10.1098/rspb.2018.2418. ISSN 0962-8452. PMC 6458320. PMID 30836875.
  11. ^ Nishihara, H.; Hasegawa, M.; Okada, N. (2006). "Pegasoferae, an unexpected mammalian clade revealed by tracking ancient retroposon insertions". Proceedings of the National Academy of Sciences. 103 (26): 9929–9934. Bibcode:2006PNAS..103.9929N. doi:10.1073/pnas.0603797103. PMC 1479866. PMID 16785431.
  12. ^ 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 (22): 2262–2267. Bibcode:2013CBio...23.2262T. doi:10.1016/j.cub.2013.09.014. PMID 24184098.
  13. ^ 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"
  14. ^ 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. Bibcode:2022Sci...376...80B. doi:10.1126/science.abl5584. hdl:20.500.11820/d7fb8c6e-886e-4c1d-9977-0cd6406fda20. PMID 35357913.
  15. ^ 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" (PDF). Journal of Anatomy. 244 (1): 1–21. doi:10.1111/joa.13951. PMC 10734658. PMID 37720992. S2CID 262047180.

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