Stirtonia victoriae, a new species of Miocene Colombian primate

Abstract

Upper jaws and other cranial material of a large primate from the Perico Member of the La Dorada Formation, Honda Group (Miocene) were discovered in 1985 and 1986. The specimens are of a new species of Stirtonia. Based on stratigraphic position, more than 300 meters below the Stirtonia tatacoensis type locality, this is the oldest primate material yet known from Colombia. Limited current evidence suggests a Santacrucian age but further geochronologic and paleontologic studies are needed to confirm this. One specimen is a nearly complete but crushed palate and lower face of a young animal. This specimen also has part of the left maxillary orbital margin and a partial left frontal with the dorsal orbital margin. A right maxilla of an old adult of the same species was found at the same locality and stratigraphic horizon. The new material resembles Stirtonia in the strong development of molar crests and stylar cusps and in many details of molar structure. We regard it as a new species because of its larger size, better developed molar crests, and because it has three-rooted rather than two-rooted P 3 and P 4. Two isolated molars from the Honda Group, previously the hypodigm of Kondous laventicus, are referred to Stirtonia talacoensis. The dental structure of Stirtonia suggests it was a leaf-eating species. A phyletic study of all Stirtonia material indicates that it is closely related to Alouatta, as R. A. Stirton first suggested and most authorities affirm.