Stirtonia (mammal)

Stirtonia is an extinct genus of New World monkeys from the Middle Miocene (Laventan in the South American land mammal ages; 13.8 to 11.8 Ma). Its remains have been found at the Konzentrat-Lagerstätte of La Venta in the Honda Group of Colombia. Two species have been described, S. victoriae and the type species S. tatacoensis.[1][2] Synonyms are Homunculus tatacoensis, described by Ruben Arthur Stirton in 1951 and Kondous laventicus by Setoguchi in 1985.[3] The genus is classified in Alouattini as an ancestor to the modern howler monkeys.[4][5]

Stirtonia
Temporal range: Middle Miocene (Laventan)
~13.5–13.0 Ma
↓
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Suborder: Haplorhini
Infraorder: Simiiformes
Family: Atelidae
Subfamily: Atelinae
Genus: †Stirtonia
Hershkovitz 1970
Species
Synonyms
  • Homunculus tatacoensis Stirton 1951
  • Kondous laventicus Setoguchi 1985

Etymology

The genus Stirtonia is named after Ruben Arthur Stirton, who has studied the La Venta primates in the 1950s and the species epithets tatacoensis and victoriae refer to the Tatacoa Desert and La Victoria Formation respectively, where the fossils have been found.

Description

The genus is the largest primate found at La Venta,[6] with estimated body masses of S. tatacoensis at 5,513 grams (12.154 lb) and of S. victoriae at 10 kilograms (22 lb).[7] Stirtonia tatacoensis and S. victoriae are known by several teeth, a mandible and a maxilla that closely resemble, and are almost indistinguishable from, the living Alouatta.[8]

Fossil teeth found in the Solimões Formation at the Acre River in the border region of Brazil and Peru may belong to Stirtonia.[6][9]

Fossil record

A lower mandible fossil of S. tatacoensis was discovered during fieldwork between 1944 and 1949,[10] in the Honda Group, that has been dated to the Laventan, about 13 Ma.

Upper jaws and other cranial material of the large primate Stirtonia victoriae from the Perico Member of the La Dorada Formation, Honda Group were discovered in 1985 and 1986. Based on stratigraphic position, more than 300 metres (980 ft) below the Stirtonia tatacoensis type locality, this was the oldest primate material known until 1987 from Colombia.[11]

Evolution
See also: Evolution of primates

The evolutionary split between Atelidae, of which Stirtonia, and Pitheciidae plus Callicebus, has been placed at 17.0 million years ago.[12]

Habitat
See also: Honda Group, Colombia § Paleoclimate and vegetation

The Honda Group, and more precisely the "Monkey Beds", are the richest site for fossil primates in South America.[13] It has been argued that the monkeys of the Honda Group were living in habitat that was in contact with the Amazon and Orinoco Basins, and that La Venta itself was probably seasonally dry forest.[14] From the same level as where Stirtonia tatacoensis has been found, also fossils of Aotus dindensis, Micodon, Mohanamico, Saimiri annectens, Saimiri fieldsi and Cebupithecia have been uncovered.[15][16][17] Stirtonia reinforced the notion that leaf-eating was an enduring and essential aspect of the howler monkey's ecophylogenetic biology.[18]

See also

References
  1. Stirtonia victoriae at Fossilworks.org
  2. Stirtonia tatacoensis at Fossilworks.org
  3. Setoguchi et al., 1986a, p.2
  4. McKenna & Bell, 1997
  5. Takai et al., 2001, p.290
  6. Defler, 2004, p.33
  7. Silvestro, 2017, p.14
  8. Pérez et al., 2013, p.4
  9. Tejedor, 2013, p.30
  10. Hershkovitz, 1970, p.1
  11. Kay et al., 1987, p.173
  12. Takai et al., 2001, p.304
  13. Rosenberger & Hartwig, 2001, p.3
  14. Lynch Alfaro et al., 2015, p.520
  15. Luchterhand et al., 1986, p.1753
  16. Wheeler, 2010, p.133
  17. Setoguchi et al., 1986b, p.762
  18. Rosenberger et al., 2015, p.24

Bibliography

Further reading
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