, Volume 11, Issue 5, pp 439-469

The phylogenetic position ofMahgarita stevensi : protoanthropoid or lemuroid?

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Abstract

This comparative study of the cranial and dental morphology ofMahgarita stevensi, which includes description of new fossil material, is designed to address hypotheses concerning the phylogenetic position ofMahgarita with respect to the Anthropoidea and tooth-combed prosimians (Lemuriformes, including Lorisoidea).Mahgarita shares with Oligocene anthropoids and primitive platyrrhines a complex assemblage of structural features that do not occur together in any tooth-combed prosimians; they include a large promontory canal and reduced or absent stapedial canal, a pneumatized petromastoid, a lateral transverse intrabullar septum and probable absence of a free annular ectotympanic, synostosed mandibular symphysis with a transverse torus, a short deep maxilla, maxillomaxillary contact on the inferior orbital margin, an upper canine with a mesial groove, a pronounced nasal spine of the palatine bone, and detailed similarities in occlusal features of the upper molars and other teeth.Mahgarita shares with tooth-combed prosimians several primitive euprimate characters, such as lack of postorbital closure and absence of intrabullar trabeculae. Previous conclusions thatMahgarita is related closely to living strepsirhines were based on a small number of primitive, gradistic features. Cranial characters that have been presented in favor of a tarsiiform-anthropoid clade are analyzed with respect toMahgarita and primitive anthropoids. The results suggest that, among known prosimians,Mahgarita is the one most closely related to the Anthropoidea.