Mixotoxodon

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, from 1,800,000—12,000 years ago.[1][2]

Mixotoxodon
Temporal range: Mid-Late Pleistocene (Uquian-Lujanian & Irvingtonian)
~1.8–0.012 Ma
↓
Mixotoxodon larensis
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Mammalia
Order:
†Notoungulata
Family:
†Toxodontidae
Subfamily:
†Haplodontheriinae
Genus:
†Mixotoxodon

Van Frank 1957
Species:
†M. larensis
Binomial name
†Mixotoxodon larensis
Van Frank 1957
Some locations where Mixotoxodon fossils have been found
Synonyms

?Mixotoxodon larensis crusafonti

Description
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 was adapted to deal with abrasive food.[3] It was a rhino-sized animal, with a weight of up to 3.8 tonnes, 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

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

 
 

Pampahippus arenalesi

 
 
 
 

Rhynchippus spp.

 
 
 

Scarritia canquelensis

 
 

Leonitinia gaudri

 
 
 
Toxodontidae
 

Proadinotherium leptognathum

 
 
 
 

Adinotherium spp.

 
 
 

Nesodon taweretus

 
 

Nesodon imbricatus

 
 
 
 
 

Palyeidodon obtusum

 
 
 

Hyperoxotodon speciosus

 
 
 
 

Nonotherium henningi

 
 

Xotodon spp.

 
 
 
 
 

Andinotoxodon bolivariensis

 
 
 
 

Dinotoxodon paranensis

 
 

Toxodon platensis

 
 
 
 

Gyrinodon quassus

 
 
 

Ocnerotherium intermedium

 
 

Hoffstetterius imperator

 
 
 
 
 
 
 

Posnanskytherium desaguaderoi

 
 
 

Pisanodon nazari

 
 
 

Pericotoxodon platignathus

 
 
 
 

Calchaquitherium mixtum

 
 

Mixotoxodon larensis

 
 
 
 

Paratrigodon euguii

 
 

Trigodon gaudri

 
 
 
 
 
 
 
 
 
 
 
 
 
 

Fossil distribution

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
  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.
  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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