Richard F. Kay, Richard H. Madden, Javier Guerrero Díaz


In the summer of 1985 we discovered an upper jaw of a large juvenile primate from the Perico member of the La Dorada Formation, Honda Group. In 1986 and 1987 we recovered additional more complete material of the same species. The 1985 type specimen and the additional material is referred to a new larger species of Stirtonia. Based on stratigraphic position, it is older than any other primate material yet known in Colombia; limited current evidence suggests a Santacrucian age. The new species resembles Stirtonia tatacoensisin having strong cheektooth shearing crests, particularly, on the buccal margins. Each of these crests terminates in a stylar cusp. lingually, cresting is less pronounced but strong. The upper incisor roots, are small compared with the size of M1. This combination of small incisors and molars with strongly developed shearing implies that the diet was folivorous resembling that of some extant large-bodied platyrrhines. Some isolated teeth we would assign to Stirtonia have been attributed by Setoguchi (1985) to another genus Kondous in or near the ancestry of Ate/es. Restudy of this material leads us to conclude that all published material fits within two species of Miocene Colombian Stirtonia. Our anaIysis shows that Stirtonia is apparently a sister-group of Alouatta, the living howling monkey, as R. A. Stirton (1951) first suggested.

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