Abstract
BackgroundThe 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 Agerinia from several fossil sites from Northeastern Spain.MethodsHere 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 Agerinia as well with other Eurasian notharctids. Furthermore, the position of the different species of Agerinia has been tested with two phylogenetic analyses.ResultsThe new material from Masia de l’Hereuet shows several traits that were previously unknown for the genus Agerinia, such as the morphology of the upper and lower fourth deciduous premolars and the P2, and the unfused mandible. Moreover, this material clearly differs from the other described species of Agerinia, A. roselli and A. smithorum, thus allowing the erection of the new species Agerinia marandati. The phylogenetic analyses place the three species of Agerinia in a single clade, in which A. smithorum is the most primitive species of this genus.DiscussionThe morphology of the upper molars reinforces the distinction of Agerinia from other notharctids like Periconodon. The analysis of the three described species of the genus, A. smithorum, A. marandati and A. roselli, reveals a progressive change in several morphological traits such as the number of roots and the position of the P1 and P2, the molarization of the P4, 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 A. smithorum) and the phylogenetic analyses developed in this work support this hypothesis.
Highlights
One of the most important steps in the early radiation of the primate clade was the appearance and diversification of Euprimates, known as true primates or primates of ‘‘modern aspect’’ (Bloch et al, 2007; Silcox et al, 2015)
The clade formed by Agerinia, sivaladapids and asiadapines would not be nested within a monophyletic Adapiformes
We present the most complete sample of the genus Agerinia described to date, coming from Masia de l’Hereuet (NE Spain)
Summary
One of the most important steps in the early radiation of the primate clade was the appearance and diversification of Euprimates, known as true primates or primates of ‘‘modern aspect’’ (Bloch et al, 2007; Silcox et al, 2015). The first records of these groups in Europe correspond to the omomyiforms Teilhardina, Melaneremia and Nannopithex and the adapiforms Donrussellia, Cantius, Protoadapis and Agerinia (Gebo, 2002; Godinot, 2015) Despite this relative diversity, the early Eocene primate record is still scarce and poorly known, preventing the establishment of clear phylogenetic relationships among known taxa. 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.
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