Laurasiatheria

Laurasiatheria is a clade of placental mammals that includes hedgehogs, even-toed ungulates, whales, bats, odd-toed ungulates, pangolins, and carnivorans, among others.[3] The clade originated on the northern supercontinent of Laurasia.[3] Its last common ancestor is supposed to have diversified ca. 76[1] to 91[2] million years ago.

Laurasiatheria
Temporal range: 76.0–0 Ma[1][2] Earliest possible: 91.0 Ma Late Cretaceous - Recent
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Magnorder: Boreoeutheria
Clade: Laurasiatheria
Waddell et al., 1999[3]
Orders

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.[6] The studies conflicted in terms of the exact placement of Chiroptera, however, with it being linked most closely to groups such as Eulipotyphla,[7] Ferae[8] or with Perissodactyla and Ferae in the Pegasoferae proposal.[9] A 2011 study 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."[10] A 2012 study supports the previous conclusions[10] using a large genomic dataset, and places Eulipotyphla as a basal order and Chiroptera as sister to Cetartiodactyla, with maximal support for all nodes of their phylogenetic tree.[11] 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', yet some authors found better (but not full) support for the latter,[10] while others found Perissodactyla to be sister to Carnivora.[11]

Two 2013 studies retrieve that chiropterans, carnivores, and euungulates form a clade, therefore involving that Eulipotyphla might be the sister group to all other Laurasiatheria taxa.[12][13]

Order-level cladogram of the Laurasiatheria (only living groups).
 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. 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. 279 (1742): 3491–3500. doi:10.1098/rspb.2012.0683. ISSN 0962-8452. PMC 3396900. PMID 22628470.
  2. 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. 61 (1): 150–64. doi:10.1093/sysbio/syr089. ISSN 1063-5157. PMC 3243735. PMID 21900649.
  3. 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.
  4. 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. Bibcode:1999PNAS...9610261N. doi:10.1073/pnas.96.18.10261. PMC 17876. PMID 10468596.
  5. Groves, Colin; Grubb, Peter (1 November 2011). Ungulate Taxonomy. JHU Press. p. 27. ISBN 978-1-4214-0093-8. OCLC 708357723.
  6. 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. Bibcode:1998JMolE..47..709P. doi:10.1007/PL00006430. PMID 9847413. S2CID 22900642.
  7. 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.
  8. 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.
  9. 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.
  10. 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.
  11. 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.
  12. 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.
  13. 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.
  14. Burger, Benjamin J., (2015.) "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

Further reading
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