Reconsidering the taxonomy of the Pithecia irrorata species group (Primates: Pitheciidae)

The number of Pithecia species has considerably increased in recent years. In the first comprehensive taxonomic revision for the genus, five species were recognized, among these, Pithecia irrorata, with two subspecies: P. irrorata irrorata and P. irrorata vanzolinii. These subspecies were elevated to full species in the most recent taxonomic revision of the genus, which was based primarily on pelage color. Additionally, it was proposed that P. irrorata was a group of undescribed species, and three additional species were described from P. irrorata: P. mittermeieri, P. rylandsi, and P. pissinattii. However, diagnoses and geographic distributions are not well defined for the species proposed, bringing confusion to subsequent studies. To address the current hypothesis on the species diversity in the P. irrorata species group, we conducted comparative analyses using the same source of evidence: pelage color variation. Material analyzed includes specimens throughout the distribution of the group in Peru, Bolivia, and Brazil. Based on our results, we recognize two groups that are morphologically diagnosable and correspond to geographically isolated populations. The senior names available for these groups are P. irrorata and P. vanzolinii. We recognize P. mittermeieri, P. rylandsi, and P. pissinattii as junior synonyms of P. irrorata. We also discuss some taxonomic inaccuracies regarding the type localities and type material for the senior and junior names, provide synonymy lists based on extensive literature review, and provide distribution maps for the valid species we recognized.