Xenarthra: Wikis

  

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Xenarthra
Fossil range: Middle Paleocene - Recent
Hoffmann's Two-toed Sloth
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Subclass: Theriiformes
Infraclass: Eutheria
Superorder: Xenarthra
Cope, 1889
Orders and suborders


See text for more details

The superorder Xenarthra is a group of placental mammals (infraclass Eutheria), extant today only in the Americas. The origins of the order can be traced back as far as the early Tertiary (about 60 million years ago, shortly after the Mesozoic era). Xenarthrans developed and diversified extensively in South America during its long period of isolation, invaded the Antilles by the early Miocene, and then spread to Central and North America starting about nine million years ago, as part of the Great American Interchange. Nearly all of the formerly abundant megafaunal xenarthrans went extinct at the end of the Pleistocene.

Xenarthrans have the lowest metabolic rates among the therians.[1][2]

Contents

Evolutionary relationships

Xenarthra includes the anteaters, tree sloths, and armadillos, as well as the extinct ground sloths, glyptodonts and pampatheres. In the past, these families were classified together with the pangolins and aardvarks as the order Edentata (meaning toothless, because the members do not have front incisor teeth or molars, or have poorly-developed molars). It was subsequently realized that Edentata was polyphyletic—that it contained unrelated families and was thus invalid by cladistic standards. Aardvarks and pangolins are now placed in individual orders, and the new order Xenarthra was erected to group the remaining families (which are all related). The name Xenarthra means "strange joints", and was chosen because their vertebral joints have extra articulations and are unlike those of any other mammals. Because they lack characteristics believed to be present in the common ancestor of other known eutherian mammals, morphological evidence suggests that the Xenarthra are outside the Epitheria, which contains all other known eutherians today.

The morphology of xenarthrans generally suggests that the anteaters and sloths are closest together within Xenarthra, which is upheld by molecular studies. The order Xenarthra is more and more often divided into two orders: Pilosa, containing the Vermilingua (anteaters) and Folivora (sloths; previously known as Tardigrada or Phyllophaga), and the separate order Cingulata (armadillos). Xenarthra now has the rank of cohort or super-order. The Xenarthra are part of the super-cohort Atlantogenata.

Xenarthra may be most closely related to either Afrotheria[3] (in the group Atlantogenata), or Epitheria[4] (comprising Afrotheria and Boreoeutheria). In other words it may be nested within Eutheria or it may be the basal extant group. A comprehensive phylogeny by Goloboff et al.[5] includes Xenarthrans as a sister clade of Boreoeutheria (Euarchontoglires+Laurasiatheria) (in the Exafroplacentalia=Notolegia).

Classification

SUPERORDER XENARTHRA

References

  1. ^ Elgar, M. A.; Harvey, P. H. (1987). "Basal Metabolic Rates in Mammals: Allometry, Phylogeny and Ecology". Functional Ecology (British Ecological Society) 1 (1): 25–36. doi:10.2307/2389354. http://www.jstor.org/stable/2389354. Retrieved 2008-04-18.  
  2. ^ Lovegrove, B. G. (2000-08). "The Zoogeography of Mammalian Basal Metabolic Rate". The American Naturalist (The University of Chicago Press) 156 (2): 201–219. doi:10.1086/303383. http://www.jstor.org/stable/3079219. Retrieved 2008-04-19.  
  3. ^ Murphy, W.J., Pringle, T.H., Crider, T.A., Springer, M.S. & Miller, W. 2007. Using genomic data to unravel the root of the placental mammal phylogeny. Genome Research 17, pp.413-421.
  4. ^ Kriegs, J.O., Churakov, G., Kiefmann, M., Jordan, U., Brosius, J. & Schmitz, J. 2006. Retroposed elements as archives for the evolutionary history of placental mammals. Plos Biol 4, pp.e91.
  5. ^ Goloboff, P.A.; Catalano, S.A.; Mirande, J.M.; Szumik, C.A.; Arias, J.S.; Källersjö, M & Farris, J.S. 2009. Phylogenetic analysis of 73 060 taxa corroborates major eukaryotic groups. Cladistics 25 (3): 211-230

External links


Wiktionary

Up to date as of January 15, 2010

Definition from Wiktionary, a free dictionary

Contents

Translingual

Etymology

This definition is lacking an etymology or has an incomplete etymology. You can help Wiktionary by giving it a proper etymology.

Proper noun

Xenarthra

  1. (taxonomy) A taxonomic superorder within the infraclass Eutheria — the anteaters, sloths, armadillos, glyptodonts, and pampatherids.

See also


Wikispecies

Up to date as of January 23, 2010

From Wikispecies

Taxonavigation

Main Page
Cladus: Eukaryota
Supergroup: Unikonta
Cladus: Opisthokonta
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Cladus: Deuterostomia
Phylum: Chordata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Superclassis: Tetrapoda
Classis: Mammalia
Subclassis: Theria
Infraclassis: Placentalia
Superordo: Xenarthra
Ordines: Cingulata - Pilosa

Name

Xenarthra Cope, 1889

Vernacular names

English: Anteaters, sloths, and armadillos
‪Norsk (bokmål)‬: Gomlere
Polski: Szczerbaki
Português: Xenartros/Desdentados
Suomi: Vajaahampaiset
Svenska: Trögdjur
Українська: Неповнозубі
Wikimedia Commons For more multimedia, look at Xenarthra on Wikimedia Commons.

Simple English

Xenarthra
Fossil range: Middle Paleocene - Recent
File:Choloepus
Hoffmann's Two-toed Sloth
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Infraclass: Eutheria
Superorder: Xenarthra
Cope, 1889
Orders and suborders

Xenarthra is a superorder of mammals.

Other pages

Look up Xenarthra in Wikispecies, a directory of species
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