Stirtonia(mammal)

Stirtonia; Temporal range:Middle Miocene(Laventan); ~13.5–13.0Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Primates
Suborder:	Haplorhini
Infraorder:	Simiiformes
Family:	Atelidae
Subfamily:	Atelinae
Genus:	†Stirtonia; Hershkovitz 1970
Species
	S. tatacoensis(Hershkovitz1970,type); S. victoriae(Kay et al. 1987);
Synonyms
	Homunculus tatacoensisStirton 1951; Kondous laventicusSetoguchi 1985;

Stirtoniais anextinct genusofNew World monkeysfrom theMiddle Miocene(Laventanin theSouth American land mammal ages;13.8 to 11.8 Ma). Its remains have been found at theKonzentrat-LagerstätteofLa Ventain theHonda GroupofColombia.Two species have been described,S. victoriaeand thetype speciesS. tatacoensis.^[1]^[2]Synonyms areHomunculus tatacoensis,described byRuben Arthur Stirtonin 1951 andKondous laventicusby Setoguchi in 1985.^[3]The genus is classified inAlouattinias an ancestor to the modernhowler monkeys.^[4]^[5]

Etymology

Stirtoniais named after the scientist who first discovered it, Ruben Arthur Stirton. The two species,S. tatcoensis and S. victoriae,are named after the locations in which they were found:S. tatacoensisgets its name from the Tatacoa desert; andS. victoriaegets its name from the village “La Victoria” near its discovery site.^[6]^[7]^[8]

Description

The genus is the largest primate found at La Venta,^[9]with estimated body masses ofS. tatacoensisat 5,513 grams (12.154 lb) and ofS. victoriaeat 10 kilograms (22 lb).^[10]Stirtonia tatacoensisandS. victoriaeare known by several teeth, a mandible and a maxilla that closely resemble, and are almost indistinguishable from, the livingAlouatta.^[11]

Fossil teeth found in theSolimões Formationat theAcre Riverin the border region ofBrazilandPerumay belong toStirtonia.^[9]^[12]

Fossil record

A lower mandible fossil ofS. tatacoensiswas discovered during fieldwork between 1944 and 1949,^[13]in theHonda Group,that has been dated to theLaventan,about 13 Ma.

Upper jaws and other cranial material of the large primateStirtonia victoriaefrom 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 theStirtonia tatacoensistype locality,this was the oldest primate material known until 1987 from Colombia.^[14]

Evolution

The evolutionary split betweenAtelidae,of whichStirtonia,andPitheciidaeplusCallicebus,has been placed at 17.0 million years ago.^[15]

Habitat

The Honda Group, and more precisely the "Monkey Beds", are the richest site forfossil primates in South America.^[16]It has been argued that the monkeys of the Honda Group were living in habitat that was in contact with theAmazonandOrinoco Basins,and that La Venta itself was probably seasonally dry forest.^[17]From the same level as whereStirtonia tatacoensishas been found, also fossils ofAotus dindensis,Micodon,Mohanamico,Saimiri annectens,Saimiri fieldsiandCebupitheciahave been uncovered.^[18]^[19]^[20]Stirtoniareinforced the notion that leaf-eating was an enduring and essential aspect of the howler monkey's ecophylogenetic biology.^[21]

References

^Stirtonia victoriaeatFossilworks.org
^Stirtonia tatacoensisatFossilworks.org
^Setoguchi et al., 1986a, p.2
^McKenna & Bell, 1997
^Takai et al., 2001, p.290
^Stirtonia Victoriaeat Fossilworks.org
^Stirtonia tatacoensisat Fossilworks.org
^Kay et al., “Stirtonia victoriae,a new species of Miocene Colombian primate”, Journal of Human Evolution, February 1987
^^a ^bDefler, 2004, p.33
^Silvestro, 2017, p.14
^Pérez et al., 2013, p.4
^Tejedor, 2013, p.30
^Hershkovitz, 1970, p.1
^Kay et al., 1987, p.173
^Takai et al., 2001, p.304
^Rosenberger & Hartwig, 2001, p.3
^Lynch Alfaro et al., 2015, p.520
^Luchterhand et al., 1986, p.1753
^Wheeler, 2010, p.133
^Setoguchi et al., 1986b, p.762
^Rosenberger et al., 2015, p.24