The enigmatic pitviper Bothrops lojanus, is an endangered snake known only in southwestern Ecuador. The present study confirms the presence of the species in northwestern Peru, extending its known distribution 307 km southward of the type locality of Loja.

We are deeply grateful to Wolfgang Wüster for his kind help and suggestions that enriched the manuscript, and to José María Gutiérrez and Gerardo Leynaud for their interest and useful comments on this work. We appreciate the constructive comments and suggestions of two anonymous reviewers. We thank Helena Shobe and Nicole Washburn for improvements in the English version of the manuscript, and Eugenia Lascano for helping with the figures edition. This work was supported by the Programa de Cooperación Científico-Tecnológica entre el Consejo Nacional de Ciencia, Tecnología e Innovación Tecnológica de Perú (CONCYTEC-FONDECYT CS-031-2014) y el Ministerio de Ciencia, Tecnología e Innovación Productiva de Argentina (MINCYT PE/13/06).

This study was partially funded by projects CLG2008-04164 and CLG2011-30393 of the Spanish government (PI: I. De la Riva), and the International Cooperation Project funded by the Consejo Nacional de Ciencia, Tecnologia e Innovacion Tecnologica (CONCYTEC, Peru) throught Fondo Nacional de Desarrollo Cientifico, Tecnologico y de Innovacion Tecnologica (FONDECYT, Peru) and the Ministerio de Ciencia, Tecnologia e Innovacion Productiva (MINCyT, Argentina) (PI. Juan C. Chaparro).