sp. nov., a new early Eocene primate from the Iberian Peninsula, sheds new light on the evolution of the genus .

Background: The Eocene was the warmest epoch of the Cenozoic and recorded the appearance of several orders of modern mammals, including the first occurrence of Euprimates. During the Eocene, Euprimates were mainly represented by two groups, adapiforms and omomyiforms, which reached great abundance and diversity in the Northern Hemisphere. Despite this relative abundance, the record of early Eocene primates from the European continent is still scarce and poorly known, preventing the observation of clear morphological trends in the evolution of the group and the establishment of phylogenetic relationships among different lineages. However, knowledge about the early Eocene primates from the Iberian Peninsula has been recently increased through the description of new material of the genus from several fossil sites from Northeastern Spain.

Methods: Here we present the first detailed study of the euprimate material from the locality of Masia de l'Hereuet (early Eocene, NE Spain). The described remains consist of one fragment of mandible and 15 isolated teeth. This work provides detailed descriptions, accurate measurements, high-resolution figures and thorough comparisons with other species of as well with other Eurasian notharctids. Furthermore, the position of the different species of has been tested with two phylogenetic analyses.

Results: The new material from Masia de l'Hereuet shows several traits that were previously unknown for the genus such as the morphology of the upper and lower fourth deciduous premolars and the P, and the unfused mandible. Moreover, this material clearly differs from the other described species of , and , thus allowing the erection of the new species . The phylogenetic analyses place the three species of in a single clade, in which is the most primitive species of this genus.

Discussion: The morphology of the upper molars reinforces the distinction of from other notharctids like . The analysis of the three described species of the genus, and , reveals a progressive change in several morphological traits such as the number of roots and the position of the P and P, the molarization of the P, the reduction of the paraconid on the lower molars and the displacement of the mental foramina. These gradual modifications allow for the interpretation that these three species, described from the early Eocene of the Iberian Peninsula, are part of a single evolutionary lineage. The stratigraphical position of Masia de l'Hereuet and Casa Retjo-1 (type locality of ) and the phylogenetic analyses developed in this work support this hypothesis.