Trigonostylops

Superregnum: Eukaryota
Cladus: Opisthokonta
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Cladus: Deuterostomia
Phylum: Chordata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Superclassis: Tetrapoda
Classis: Mammalia
Subclassis: Theria
Infraclassis: Placentalia
Superordo: †Meridiungulata
Ordo: Astrapotheria
Familia: Trigonostylopidae
Genus: Trigonostylops

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Trigonostylops is an extinct genus of South American meridiungulatan ungulate, from the Late Paleocene to Late Eocene (Itaboraian to Tinguirirican in the SALMA classification) of South America (Argentina and Peru) and Antarctica (Seymour Island). It is the only member of the family Trigonostylopidae.

Description
Interpretation of T. wortmani

A complete skull of the type species, T. wortmani, has been found, and it has been classified as an astrapothere based on its large lower tusks. In comparison with the later Astrapotherium magnum, it is estimated to have been around 1.50 metres (4.9 ft) long.[1] Teeth, primarily molars, have been found and assigned to other species.
Phylogeny

Cladogram based in the phylogenetic analysis published by Vallejo Pareja et al., 2015, showing the position of Trigonostylops:[2]
 

	Eoastrapostylops
	Trigonostylops       Tetragonostylops       Albertogaudrya       Scaglia       Astraponotus       Maddenia       Comahuetherium       Parastrapotherium     Astrapotheriinae   Astrapotherium     Astrapothericulus     Uruguaytheriinae   Uruguaytherium         Hilarcotherium     Xenastrapotherium       Granastrapotherium

 
Distribution
Fossils of Trigonostylops have been found in:[3]

Paleocene

Las Flores Formation, Argentina[4]

Eocene

La Meseta Formation, Antarctica[5]
Casamayor, Divisadero Largo, Koluel Kaike and Sarmiento Formations, Argentina[6][7]
Pozo Formation, Peru[8]

References

iconPaleontology portal Prehistoric mammals portal

Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 249. ISBN 978-1-84028-152-1.
Vallejo Pareja et al., 2015
Trigonostylops at Fossilworks.org
Goin et al., 2009
Dzik & Gaździcki, 2001
Vera, 2012
Cifelli, 29185, p.5

Antoine et al., 2011

Bibliography

Antoine, P.O.; L. Marivaux; D.A. Croft; G. Billet; M. Ganerod; C. Jaramillo; T. Martin; M. Orliac, and J. Tejada, A. J. Altamirano, F. Duranthon, G. Fanjat, S. Rousse and R. Salas Gismondi. 2011. Middle Eocene rodents from Peruvian Amazonia reveal the pattern and timing of caviomorph origins and biogeography. Proceedings of the Royal Society B 279. 1319–1326. Accessed 2019-02-14.
Cifelli, R. 1985. Biostratigraphy of the Casamayoran, Early Eocene of Patagonia. American Museum Novitates 2820. 1–26. Accessed 2019-02-14.
Dzik, J., and A. Gaździcki. 2001. The Eocene expansion of nautilids to high latitudes. Palaeogeography, Palaeoclimatology, Palaeoecology 172. 297–312. Accessed 2019-02-14.
Goin, F.J.; A.M. Candela; M.A. Abello, and E.V. Oliveira. 2009. Earliest South American paucituberculatans and their significance in the understanding of ‘pseudodiprotodont’ marsupial radiations. Zoological Journal of the Linnean Society 155. 867–884. Accessed 2019-02-14.
Vallejo Pareja, M.C.; J.D. Carrillo; J.W. Moreno Bernal; M. Pardo Jaramillo; D.F. Rodríguez González, and J. Muñoz Duran. 2015. Hilarcotherium castanedaii, gen. et sp. nov., a new Miocene astrapothere (Mammalia, Astrapotheriidae) from the Upper Magdalena Valley, Colombia. Zurich Open Repository and Archive, University of Zurich _. 1–14. Accessed 2019-02-14.
Vera, B. 2012. Revisión del género Transpithecus Ameghino, 1901 (Notoungulata, Interatheriidae) del Eoceno medio de Patagonia, Argentina. Ameghiniana 49. 60–74. Accessed 2019-02-14.