''Rosendo'' is an extinct genus of notohippid notoungulates that lived during the Early Oligocene in what is now Argentina and Chile. Fossils of this genus have been found in the

Sarmiento Formation The Sarmiento Formation (Spanish: ''Formación Sarmiento''), in older literature described as the Casamayor Formation, is a geological formation in Chubut Province, Argentina, in central Patagonia, which spans around 30 million years from the mid- ...

and the Abanico Formations of Argentina and Chile.

Description

''Rosendo'' was approximately the size of a goat, albeit with a more robust build. It had a heavy and sturdy skull, with a relatively short muzzle. The dentition was characterized by high-crowned (hypsodont) incisors, posterior premolars and molars. The teeth didn't have cementum. The upper incisors were slightly protruding forward. The third upper incisor was wider than the other two, while the fourth premolar was more molariform than the other premolars, but devoid of a distinct hypocone. The upper molars had hypocones, with a variable but generally deep fissure separating them from the protocones. The fissure was blocked by the medial projection of a hooked structure. Apart from the permanent major fossa, the other fossae are erased with wear.

Taxonomy

The genus ''Rosendo'' was first described in 2018 by André R. Wyss, based on fossil remains found in Patagonia, in deposits dated to the Early Oligocene. The type species is ''Rosendo pascuali'', whose fossils have also been found in the Sarmiento Formation of Chubut Province, Argentina, as well as the Abanico Formation of Chile. Historically, the genus was originally attributed to the genus '' Eomorphippus'' in 1967, described by George Gaylord Simpson, but was subsequently found to be a distinct genus in 2018. ''Rosendo'' is a toxodont, a clade of notoungulates, that developed a remarkable diversity of forms during the

Cenozoic The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configura ...

. ''Eomorphippus'' has been historically included within the family

Notohippidae Notohippidae is a paraphyletic extinct family of notoungulate mammals from South America. Notohippids are known from the Eocene and Oligocene epochs.McKenna, Malcolm C., and Bell, Susan K. 1997. ''Classification of Mammals Above the Species Leve ...

, which included several genera whose hypsodont teeth were similar to those of horses. This family, however, is no longer considered

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...

. The following position of the Toxodontia is based on Martínez ''et al.'' 2021, showing the position of ''Rosendo''.

References

{{Taxonbar, from=Q115794183 Toxodonts Prehistoric placental genera Oligocene mammals of South America Paleogene Argentina Paleogene Chile Fossils of Argentina Fossils of Chile Tinguirirican Fossil taxa described in 2018 Golfo San Jorge Basin Sarmiento Formation