Stegomastodon
Temporal range: Pliocene-Early Pleistocene
~ (possible Late Pleistocene record)
S. mirificus fossil at the Smithsonian Natural History Museum
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Proboscidea
Family: †Gomphotheriidae
Genus: †Stegomastodon
Pohlig, 1912
Species
  • †S. aftoniae
  • †S. mirificus
  • †S. nebrascensis
  • †S. primitivus
Synonyms
  • Morrillia

Stegomastodon ('roof breast tooth') is an extinct genus of gomphotheres, a family of proboscideans. It ranged throughout North America from the early Blancan ~4 Ma, to the early Irvingtonian (~1.2 Ma). The South American species have been synonymized with Notiomastodon platensis.

Species

The following definite species have been described:[1]

  • S. aftoniae
  • S. mirificus
  • S. nebrascensis
  • S. primitivus

S. waringi is considered synonymous with S. platensis. A dispute now exists over whether S. platensis should remain within the North and Central American genus Stegomastodon or should be moved over to the exclusively South American genus Notiomastodon.[2][3][4] The genus Haplomastodon is regarded as synonymous with the South American Stegomastodon species.[5][6]

Origin and evolution

Stegomastodon is considered by some to be derived from New World populations of Gomphotherium. The number of species within the genus has varied between S. mirificus being the only valid species, to Osborn's seven species of “ascending mutations” (S. primitivus, S. successor, S. mirificus, S. chapmani, S. texanus, S. arizonae and S. aftoniae) Lucas et al., 2013 accepted 3 overlapping chronospecies S. primitivus, S. mirificus S. aftoniae.[7]

Description

Restoration of a S. mirificus herd

Stegomastodon mirificus is known from NMNH 10707, a roughly 30-year-old male, of which most of the skeleton has been found. Alive, it stood about 2.6 m (8.5 ft) tall, with a weight around 4.7 tonnes (4.6 long tons; 5.2 short tons).[8] Like modern elephants, but unlike most of its closer relatives, it had just two tusks, which curved upward and were about 3.5 m (11.5 ft) long. The tall, head and robust lower jaw suggest a strong vertical bite. Stegomastodon's molars were covered in enamel and had a complex pattern of ridges and knobbly protrusions on them, giving the creature a large chewing surface that suggests it was a grazer.[7] During the early Irvingtonian, Stegomastodon was replaced by Mammuthus, which was presumably a more efficient grazer. Its brain weighed about 11 lb (5 kg).

The genus lived in North America from the Pliocene to the early Pleistocene. Originally, some specimens from Jalisco, Mexico were estimated to date to 28,000 BP,[9], but this age was rejected in 2011 by Spencer G. Lucas et. al, who stated that the date was far too young to be viable and that it actually dates to the Blancan (3-4 Ma).[10]

Taxonomy

Restoration of S. mirificus

The South American Stegomastodon fossils were reassigned to Notiomastodon,[11] though in literature the outdated genus and species names continued to be used until 2016.[12]


Revised taxonomy of Stegomastodon and other trilophodont gomphotheres according to Mothé et al., 2017:[13]

†Gomphotheriidae (Gomphotheres)

†Gomphotherium

†Gnathabelodon

†Eubelodon

Brevirostrine clade

†Stegomastodon

†Sinomastodon

†Notiomastodon

†Rhynchotherium

†Cuvieronius

References

  1. ↑ Stegomastodon at Fossilworks.org
  2. ↑ Labarca, R.; Alberdi, M.T.; Prado, J.L.; Mansilla, P.; Mourgues, F.A. (18 April 2016). "Nuevas evidencias acerca de la presencia de Stegomastodon platensis Ameghino, 1888, Proboscidea: Gomphotheriidae, en el Pleistoceno tardío de Chile central/New evidences on the presence of Stegomastodon platensis Ameghino, 1888, Proboscidea: Gomphotheriidae, in the Late Pleistocene of Central Chile". Estudios Geológicos. 72.
  3. ↑ Mothé, Dimila; dos Santos Avilla, Leonardo; Asevedo, Lidiane; Borges-Silva, Leon; Rosas, Mariane; Labarca-Encina, Rafael; Souberlich, Ricardo; Soibelzon, Esteban; Roman-Carrion, José Luis; Ríos, Sergio D.; Rincon, Ascanio D.; Cardoso de Oliveira, Gina; Pereira Lopes, Renato (30 September 2016). "Sixty years after 'The mastodonts of Brazil': The state of the art of South American proboscideans (Proboscidea, Gomphotheriidae)" (PDF). Quaternary International. 443: 52–64. Bibcode:2017QuInt.443...52M. doi:10.1016/j.quaint.2016.08.028.
  4. ↑ Mothé, Dimila; Ferretti, Marco P.; Avilla, Leonardo S. (2017-06-03). "Running Over the Same Old Ground: Stegomastodon Never Roamed South America". Journal of Mammalian Evolution. 26 (2): 165–177. doi:10.1007/s10914-017-9392-y. ISSN 1064-7554. S2CID 23041930.
  5. ↑ Lucas, Spencer G.; Yuan, Wang; Min, Liu (2013-01-01). "The palaeobiogeography of South American gomphotheres". Journal of Palaeogeography. 2 (1): 19–40. Bibcode:2013JPalG...2...19L. doi:10.3724/SP.J.1261.2013.00015 (inactive 1 August 2023).{{cite journal}}: CS1 maint: DOI inactive as of August 2023 (link)
  6. ↑ Dantas, Mário André Trindade; Xavier, Márcia Cristina Teles; França, Lucas de Melo; Cozzuol, Mario Alberto; Ribeiro, Adauto de Souza; Figueiredo, Ana Maria Graciano; Kinoshita, Angela; Baffa, Oswaldo (2013-12-13). "A review of the time scale and potential geographic distribution of Notiomastodon platensis (Ameghino, 1888) in the late Pleistocene of South America" (PDF). Quaternary International. Quaternary in South America: recent research initiatives. 317: 73–79. Bibcode:2013QuInt.317...73D. doi:10.1016/j.quaint.2013.06.031.
  7. 1 2 Lucas, Spencer G. Taxonomy and evolution of the Plio-Pleistocene proboscidean Stegomastodon in North America. OCLC 798103439.
  8. ↑ Larramendi, A. (2016). "Shoulder height, body mass and shape of proboscideans" (PDF). Acta Palaeontologica Polonica. 61. doi:10.4202/app.00136.2014. S2CID 2092950.
  9. ↑ Alberdi, María Teresa; Juárez-Woo, Javier; Polaco, Oscar J.; Arroyo-Cabrales, Joaquín (2009-02-01). "Description of the most complete skeleton of Stegomastodon (Mammalia, Gomphotheriidae) recorded for the Mexican Late Pleistocene". Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen. 251 (2): 239–255. doi:10.1127/0077-7749/2009/0251-0239.
  10. ↑ Lucas, Spencer G.; Aguilar, Ricardo H.; Speilmann, Justin A. (2011). "Stegomastodon (Mammalia, Proboscidea) from the Pliocene of Jalisco, Mexico and the species-level taxonomy of Stegomastodon". New Mexico Museum of Natural History and Science Bulletin. 53: 517–553.
  11. ↑ Mothé, Dimila; Avilla, Leonardo S.; Cozzuol, Mário; Winck, Gisele R. (25 October 2012). "Taxonomic revision of the Quaternary gomphotheres (Mammalia: Proboscidea: Gomphotheriidae) from the South American lowlands". Quaternary International. 276–277: 2–7. Bibcode:2012QuInt.276....2M. doi:10.1016/j.quaint.2011.05.018.
  12. ↑ Labarca, Rafael; Alberdi, María Teresa; Prado, José Luis; Mansilla, P.; Mourgues, F.A. (2016). "Nuevas evidencias acerca de la presencia de Stegomastodon platensis Ameghino, 1888, Proboscidea: Gomphotheriidae, en el Pleistoceno tardío de Chile central". Estudios Geológicos. 72: e046. doi:10.3989/egeol.42199.385. hdl:10261/192918.
  13. ↑ Mothé, Dimila; dos Santos Avilla, Leonardo; Asevedo, Lidiane; Borges-Silva, Leon; Rosas, Mariane; Labarca-Encina, Rafael; Souberlich, Ricardo; Soibelzon, Esteban; Roman-Carrion, José Luis; Ríos, Sergio D.; Rincon, Ascanio D.; de Oliveira, Gina Cardoso; Lopes, Renato Pereira (2 July 2017). "Sixty years after 'The mastodonts of Brazil': The state of the art of South American proboscideans (Proboscidea, Gomphotheriidae)". Quaternary International. 443: 52–64. Bibcode:2017QuInt.443...52M. doi:10.1016/j.quaint.2016.08.028.
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