Mixotoxodon

Mixotoxodon
Temporal range: ?early to late Pleistocene[1]
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 (De Porta, 1959)[2]

Mixotoxodon ("mixture Toxodon") is an extinct genus of notoungulate of the family Toxodontidae which inhabited South America, Central America and parts of southern North America during the Pleistocene, living from 1.8—0.30 Ma and existing for approximately 1.5 million years.[3]

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 the 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 incisives 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.[4] It was a rhino-sized animal, with a weight of up to 3.8 tonnes, which make it the largest member of Notoungulata.[5]

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,[6] in Veracruz and Michoacán, Mexico (with a possible find in Tamaulipas),[7] and eastern Texas, USA.[8] 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.[9]

Phylogeny

The cladogram below is based in the study made by Analía Forasiepi and colleagues (2014), showing the position of Mixotoxodon inside Toxodontidae:[10]

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,[11] unless otherwise indicated:

Notes

  1. ↑ McKenna & Bell, 1997, p. 461.
  2. ↑ De Porta 1959, p. 55.
  3. ↑ Paleobiology Database: Mixotoxodon, Basic info.
  4. ↑ Paula-Couto, 1979, p. 404.
  5. ↑ Elissamburu, 2012, p. 108.
  6. ↑ McKenna & Bell, 1997, p. 461; Cisneros, 2005, p. 246.
  7. ↑ Arroyo-Cabrales et al., 2010, pp. 193-194
  8. ↑ Lundelius et al., p. 229.
  9. ↑ van Frank, 1957, p. 6.
  10. ↑ 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. doi:10.1007/s12542-014-0233-5.
  11. ↑ Rincón 2011, p. 896.
  12. ↑ Lundelius et al., 2013, p.229
  13. ↑ Chimento & Agnolin, 2011, p. 90.

References