Notostylops sp.

Tejedor, Marcelo F., Goin, Francisco J., Gelfo, Javier N., López, Guillermo, Bond, Mariano, Carlini, Alfredo A., Scillato-Yané, Gustavo J., Woodburne, Michael O., Chornogubsky, Laura, Aragón, Eugenio, Reguero, Marcelo A., Czaplewski, Nicholas J., Vincon, Sergio, Martin, Gabriel M. & Ciancio, Martín R., 2009, New Early Eocene Mammalian Fauna from Western Patagonia, Argentina, American Museum Novitates 3638, pp. 1-43 : 25

Notostylops sp.

Mandibular fragments and isolated upper teeth that can be referred to the genus Notostylops are abundant in both localities of Paso del Sapo. However, their specific attribution is difficult. Notostylops has been found in the upper levels of the Riochican (i.e., in the Ernestokokenia chaishoer faunal zone), and in the Casamayoran sensu lato (Vacan and Barrancan subages).

It is important to note that, although the lower molars of Notostylops and Homalostylops are very similar morphologically, there is a significant difference in size.

Family Oldfieldthomasiidae ( Simpson, 1945)

This family includes small- to moderate-sized ungulates with a generalized crown morphology, thus being basal with respect to the Typotheria-Hegetotheria radicle. The oldest oldfieldthomasiids are from the Itaboraian of Brazil and Patagonia (Pascual and Ortíz Jaureguizar, 1992), and one of its taxa, Kibenikhoria Simpson (1935a) , characterizes the middle levels of the Riochican (‘‘ Kibenikhoria faunal zone’’; see Simpson, 1935b). The youngest record of this family is from the Fray Bentos Formation in Uruguay ( Ubilla et al., 1999).

Gen. et. sp. indet. I

Some mandibular fragments collected in Laguna Fría show simple molars with open trigonids, transversely crestlike entoconid, not fully fused to the hypolophid and separated from the metaconid by a deep sulcus. This morphology is certainly related to the Oldfieldthomasiidae . The diagnostic characters for the oldfieldthomasiid species are generally for the upper molariforms; therefore, these lower materials are here described as Gen. et. sp. indet. However, the general morphology, crown height, and size closely approximate the genus Kibenikhoria (e.g., LIEB-PV 1658).

Family Archaeopithecidae ( Ameghino, 1897)

This family includes small, generalized notoungulates with relatively high-crowned molars, recorded from the ‘‘ Ernestokokenia chaishoer faunal zone’’, (Upper Riochican; see Simpson, 1935b) and they were relatively abundant up to Mustersan levels ( Cladera et al., 2004).