Laurasiatheria

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Laurasiatheria
Temporal range: Late Cretaceous - Recent
Laurasiatherians of different orders: Erinaceomorpha, Perissodactyla, Chiroptera, Cetartiodactyla, Carnivora and Pholidota.
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Subphylum:
Vertebrata
Class:
Mammalia
Subclass:
Theria
Infraclass:
Placentalia
Magnorder:
Boreoeutheria
Superorder:
Laurasiatheria

Waddell et al., 1999[1]
Orders

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

A 2013 study by Tsagkogeorga, et al. suggests that the carnivores, cetaceans, chiroptera, and ungulates form an ancient clade.[10] This is supported by a study by Morgan, et al. (2013) that suggests that Eulipotyphla are the earliest diverging clade within the Laurasiatheria.[11]

Order-level cladogram of the Laurasiatheria.
 Boreoeutheria 

 Euarchontoglires
 (primates, colugos, treeshrews, rodents, rabbits) 

 Laurasiatheria 

 Eulipotyphla
 (hedgehogs, shrews, moles, solenodons) 

 Scrotifera 

 Chiroptera
 (bats and flying foxes) 

 Ferungulata 
 Ferae 

 Pholidota
 (pangolins) 

 Carnivora
 (cats, hyenas, dogs, bears, seals, etc.) 

 Euungulata 

 Perissodactyla
  (horses, tapirs, rhinos, etc.)

 Cetartiodactyla
 (camels, pigs, ruminants, hippos, whales, etc.) 

The cladogram has been reconstructed from mitochondrial and nuclear DNA and protein characters.

Laurasiatheria is also posited to include several extinct orders and superorders. At least some of these are considered wastebasket taxa, 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.

See also

References

  1. ^ Waddell, Peter J.; Okada, Norihiro; 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 17876. PMID 10468596. {{cite journal}}: Unknown parameter |last-author-amp= ignored (|name-list-style= suggested) (help)
  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 1479866. 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 3243735. 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. ^ Tsagkogeorga, G; Parker, J; Stupka, E; Cotton, J.A.; Rossiter, S.J. (2013). "Phylogenomic analyses elucidate the evolutionary relationships of bats". Current Biology. 23 (22): 2262–2267. doi:10.1016/j.cub.2013.09.014. PMID 24184098.
  11. ^ Morgan, C.C.; Foster, P.G.; Webb, A.E.; Pisani, D; McInerney, J.O.; O'Connell, M.J. (2013). "Heterogeneous models place the root of the placental mammal phylogeny". Molecular Biology and Evolution. 30 (9): 2145–2256. doi:10.1093/molbev/mst117. PMC 3748356. PMID 23813979.
  12. ^ 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, Utah, 2015

Further reading

External links

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