Laurasiatheria

Laurasiatheria
Temporal range: Late Cretaceous - Recent
Clockwise from the upper left: giraffe, golden crown fruit bat, lion, hedgehog
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Class: Mammalia
Magnorder: Boreoeutheria
Superorder: Laurasiatheria
Waddell et al., 1999[1]
Orders

Laurasiatheria is a superorder of placental mammals that originated on the northern supercontinent of Laurasia 99 million years ago. The superorder includes shrews, pangolins, bats, whales, carnivorans, odd-toed and even-toed ungulates, among others.

Classification and phylogeny

Laurasiatheria was discovered on the basis of the similar gene sequences shared by the mammals belonging to it; no anatomical features have yet been found that unite the group. Laurasiatheria is a clade usually discussed without a Linnaean rank, but has been assigned the rank of cohort or magnorder, and superorder. The Laurasiatheria clade is based on DNA sequence analyses and retrotransposon presence/absence data. The name comes from the theory that these mammals evolved on the supercontinent of Laurasia, after it split from Gondwana when Pangaea broke up. It is a sister group to Euarchontoglires (or Supraprimates) with which it forms the clade Boreoeutheria. Laurasiatheria includes the following extant taxa:

Uncertainty still exists regarding the phylogenetic tree for extant laurasiatherians, primarily due to disagreement about the placement of Chiroptera and Perissodactyla. Based on morphological grounds, Chiroptera had long been classified in the superorder Archonta (e.g. along with treeshrews and the gliding colugos) until genetic research instead showed their kinship with the other laurasiatherians.[4] The studies conflicted in terms of the exact placement of Chiroptera, however, with it being linked most closely to groups such as Eulipotyphla,[5] Ferae[6] or with Perissodactyla and Ferae in the Pegasoferae proposal.[7] A recent study (Zhou et al., 2011[8]) found that "trees reconstructed [...] for the 1,608-gene data set fully support [...] a basal position for Eulipotyphla and a more apical position for Chiroptera" (see cladogram below) and concluded that "Pegasoferae [...] does [sic] not appear to be a natural group." The most recent study (Nery et al., 2012[9]) supports the conclusions of Zhou et al. using a large genomic dataset, placing Eulipotyphla as a basal order and Chiroptera as sister to Cetartiodactyla, with maximal support for all nodes of their phylogenetic tree. The exact position of Perissodactyla remains less certain, with some studies linking it with Ferae into a proposed clade Zooamata while others unite it with Cetartiodactyla into Euungulata, a clade of 'true ungulates'; Zhou et al. found better (but not full) support for the latter, while Nery et al. found Perissodactyla to be sister to Carnivora.

Boreoeutheria
   Laurasiatheria   

 Eulipotyphla


   Scrotifera   

 Chiroptera


   Fereuungulata   
   Ferae   

 Pholidota

 Carnivora



   Euungulata   

 Perissodactyla    

 Artiodactyla (includes Cetacea (whales and dolphins), also called Cetartiodactyla)

Euarchontoglires



Laurasiatheria is also posited to include several extinct orders and superorders. At least some of these are considered wastebasket taxons, historically lumping together several lineages based on superficial attributes and assumed relations to modern mammals. In some cases, these orders have turned out to either be paraphyletic assemblages, or to be composed of mammals now understood not to be laurasiatheres at all.

References

  1. ↑ Waddell, Peter J.; Okada, Norohiro; Hasegawa, Masami (1999). "Towards Resolving the Interordinal Relationships of Placental Mammals". Systematic Biology. 48 (1): 1–5. doi:10.1093/sysbio/48.1.1. PMID 12078634.
  2. ↑ Nikaido, M., Rooney, A. P. & Okada, N. (1999). "Phylogenetic relationships among cetartiodactyls based on insertions of short and long interpersed elements: Hippopotamuses are the closest extant relatives of whales". Proceedings of the National Academy of Sciences. 96 (18): 10261–10266. doi:10.1073/pnas.96.18.10261. PMC 17876Freely accessible. PMID 10468596. Retrieved 3 October 2011.
  3. ↑ Groves, Colin; Grubb, Peter (1 November 2011). Ungulate Taxonomy. JHU Press. p. 27. ISBN 978-1-4214-0093-8. OCLC 708357723.
  4. ↑ Pumo, Dorothy E.; Finamore, Peter S.; Franek, William R.; Phillips, Carleton J.; Tarzami, Sima; Balzarano, Darlene (1998). "Complete Mitochondrial Genome of a Neotropical Fruit Bat, Artibeus jamaicensis, and a New Hypothesis of the Relationships of Bats to Other Eutherian Mammals". Journal of Molecular Evolution. 47 (6): 709–717. doi:10.1007/PL00006430. PMID 9847413.
  5. ↑ Cao, Ying; Fujiwara, Miyako; Nikaido, Masato; Okada, Norihiro; Hasegawa, Masami (2000). "Interordinal relationships and timescale of eutherian evolution as inferred from mitochondrial genome data". Gene. 259 (1–2): 149–158. doi:10.1016/S0378-1119(00)00427-3. PMID 11163972.
  6. ↑ Matthee, Conrad A.; Eick, Geeta; Willows-Munro, Sandi; Montgelard, Claudine; Pardini, Amanda T.; Robinson, Terence J. (2007). "Indel evolution of mammalian introns and the utility of non-coding nuclear markers in eutherian phylogenetics". Molecular Phylogenetics and Evolution. 42 (3): 827–837. doi:10.1016/j.ympev.2006.10.002. PMID 17101283.
  7. ↑ 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. doi:10.1073/pnas.0603797103. PMC 1479866Freely accessible. PMID 16785431.
  8. ↑ Zhou, Xuming; Xu, Shixia; Xu, Junxiao; Chen, Bingyao; Zhou, Kaiya; Yang, Guang (2011). "Phylogenomic Analysis Resolves the Interordinal Relationships and Rapid Diversification of the Laurasiatherian Mammals". Systematic Biology. 61 (1): 150–164. doi:10.1093/sysbio/syr089. PMC 3243735Freely accessible. PMID 21900649.
  9. ↑ Nery, M. F.; González, D. M. J.; Hoffmann, F. G.; Opazo, J. C. (2012). "Resolution of the laurasiatherian phylogeny: Evidence from genomic data". Molecular Phylogenetics and Evolution. 64 (3): 685–689. doi:10.1016/j.ympev.2012.04.012. PMID 22560954.
  10. ↑ BURGER, Benjamin J., THE SYSTEMATIC POSITION OF THE SABER-TOOTHED AND HORNED GIANTS OF THE EOCENE: THE UINTATHERES (ORDER DINOCERATA), Utah State University Uintah Basin Campus, Vernal, UT, United States of America, 84078 , SVP 2015

Further reading

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