Abstract

This study constitutes the first evolutionary investigation that adds Venezuelan species of sleepyhead snakes of the genus Atractus, the most diverse and with the largest number of species with a restricted distribution area above 1000 m asl, whose estimated divergence occurred 21–22 MY. In this context, phylogenetic analyses using a combination of mitochondrial (16S, Cytb, ND4) and nuclear (RAG1, NT3) markers within the framework of maximum likelihood and Bayesian models, as well as morphological and meristic data, support the recognition of two new species that inhabit montane semideciduous forests and cloud forests between 1800 and 2200 m asl: A. nemosophis sp. nov. a polymorphic species related to A. meridensis, instead, A. xaxi sp. nov. exhibits a uniform dorsal pattern very closely with A. mariselae and A. mijaresi, respectively. Finally, we provide new data on the diversity and distribution of the Atractus from the cordillera de Mérida, including a dichotomous key and a novel perception of their conservation status when considered the most diverse and dominant snakes of the Andean Mountain landscapes. Atractus nemosophis sp. nov. and Atractus xaxi sp. nov. should be included in the Vulnerable category according to criteria Ac and B2 (i,ii,iii,iv). © Gesellschaft für Biologische Systematik 2025.