Simpsonotus is an extinct genus of notoungulate mammals in the family Henricosborniidae from the Middle to Late Paleocene of South America. Fossils of the genus have been found in the Mealla Formation, a fluvial and lacustrine sedimentary unit of the Salta Basin in northwestern Argentina.Sánchez & Marquillas, 2009, p.389Narváez, 2009, p.172 The genus name honors paleontologist George Gaylord Simpson.
Description Simpsonotus had a skull similar to Notostylops, but with a shorter and rounder face. The genus contains two species; the type species S. praecursor,S. praecursor at Fossilworks.org and the double-sized S. major,S. major at Fossilworks.org both described by Pascual et al. in 1978.Pascual et al., 1978
Age The Mealla Formation was initially described as Riochican in the South American land mammal age classification, and later as Itaboraian, but after the redefinition of the Itaboraí Formation to Early Eocene, the Mealla Formation is Peligran in age.
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