Mixotoxodon

Mixotoxodon
Life restoration of Mixotoxodon larensis
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Notoungulata
Family: Toxodontidae
Subfamily: Toxodontinae
Genus: Mixotoxodon
Van Frank 1957
Species:
M. larensis
Binomial name
Mixotoxodon larensis
Van Frank 1957
Some locations where Mixotoxodon fossils have been found

Mixotoxodon ("mixture Toxodon") is an extinct genus of notoungulate of the family Toxodontidae inhabiting South America, Central America and parts of southern North America during the Pleistocene epoch, from 1,800,000—12,000 years ago.[1][2]

Description

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Hypothetical reconstruction of the skull of M. larensis, based in different specimens.

Mixotoxodon is known by fragmentary remains, usually mandible fragments and teeth. Although the general appearance probably was very similar to another toxodontid from the Pleistocene, the better known Toxodon, their fossils shown that the outer borders of the symphysis in the lower jaw don't diverge anteriorly, and the incisors form a semicircular structure that protrude less than the incisors of Toxodon; the snout was cylindrical, instead of the broad hippo-like muzzle of Toxodon. The straight snout and the narrow lower incisors closely packed, suggest that this animal had a different feeding strategy compared to their southern relative, although the teeth of both genera were adapted to deal with abrasive food.[3] It was a rhino-sized animal, with a weight of up to 3.8 tonnes (4.2 short tons), which makes it the largest member of Notoungulata.[4]

Mixotoxodon is known from a single species, M. larensis. Mixotoxodon is the only notoungulate known to have migrated out of South America during the Great American Interchange. Its fossils have been found in northern South America, in Central America,[5][6] in Veracruz and Michoacán, Mexico (with a possible find in Tamaulipas),[7][8][9] and eastern Texas, USA.[10] The genus was also one of the last surviving notoungulates, along with related genera such as the better-known Toxodon. The name refers to the fact that Mixotoxodon combines characteristics typical of different toxodontid subfamilies.[11]

Phylogeny

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The cladogram below is based in the study published by Analía Forasiepi and colleagues (2014), showing the position of Mixotoxodon inside Toxodontidae:[12]

Fossil distribution

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This list indicates the countries and places where Mixotoxodon fossils have been found. The list follows Rincón, 2011,[13] unless otherwise indicated:

North America
South America

References

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  1. ^ Mixotoxodon at Fossilworks.org
  2. ^ "NEW REMAINS OF Mixotoxodon larensis Van Frank 1957 (Mammalia: Notoungulata) FROM MENE DE INCIARTE TAR PIT, NORTH-WESTERN VENEZUELA Ascanio D. Rincó" (PDF).
  3. ^ Paula-Couto, 1979, p. 404.
  4. ^ Elissamburu, 2012, p. 108.
  5. ^ McKenna & Bell, 1997, p. 461; Cisneros, 2005, p. 246.
  6. ^ "NEW REMAINS OF Mixotoxodon larensis Van Frank 1957 (Mammalia: Notoungulata) FROM MENE DE INCIARTE TAR PIT, NORTH-WESTERN VENEZUELA Ascanio D. Rincó" (PDF).
  7. ^ Arroyo-Cabrales et al., 2010, pp. 193-194
  8. ^ "A New Occurrence of Toxodonts in the Pleistocene of México". ResearchGate. Retrieved 2016-01-23.
  9. ^ Lucas, Spencer G.; Morgan, Gary S.; Spielmann, Justin A.; Prothero, Donald R. (2008-01-01). Neogene Mammals: Bulletin 44. New Mexico Museum of Natural History and Science.
  10. ^ Lundelius et al., p. 229.
  11. ^ van Frank, 1957, p. 6.
  12. ^ Forasiepi, A. A. M.; Cerdeño, E.; Bond, M.; Schmidt, G. I.; Naipauer, M.; Straehl, F. R.; Martinelli, A. N. G.; Garrido, A. C.; Schmitz, M. D.; Crowley, J. L. (2014). "New toxodontid (Notoungulata) from the Early Miocene of Mendoza, Argentina". Paläontologische Zeitschrift. 89 (3): 611–634. doi:10.1007/s12542-014-0233-5. hdl:11336/20443. S2CID 129293436.
  13. ^ Rincón 2011, p. 896.
  14. ^ Lundelius et al., 2013, p.229
  15. ^ Chimento & Agnolin, 2011, p. 90

Bibliography and further reading

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