LAUSR

We provide information about the composition of the terrestrial frogs of the genus Pristimantis in the upper basin of the Upano River, located on the Eastern slope of the Andes Mountain range in the Morona Santiago province, south-east of Ecuador. The compendium of the 37 species comes from collections conducted on an altitudinal gradient of between 1170 to 3750 meters. Four species are described as new: Pristimantis albujai sp. nov, P. churuwiai sp. nov, P. sambalan sp. nov and P. saturtinoi sp. nov. Two species are reported for the first time in Morona Santiago, expanding their known distribution. Eight species have an undetermined taxonomic status, which could represent new additions to Ecuador’s fauna. Of the 28 species formally described, 16 are endemic to the eastern slopes of the Ecuadorean Andes, and eight are restricted to the upper sub-basin of the Upano River. The highest concentration of diversity occurs between 1200 to 1600 meters of elevation, diminishing as the altitude increases. Our survey represents 45.5% of the Pristimantis frogs reported for the upper basin of the Napo, Pastaza and Santiago rivers.