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The frog Pristimantis marmoratus was originally described as Hylodes marmoratus by George A. Boulenger in 1900 based on a single specimen reported to have been collected at the foot of Mount Roraima in Guyana in 1898. We herein discuss the exact location of the type locality of P. marmoratus and provide a redescription of the species based on new material from Kaieteur National Park and from the slopes of Maringma-tepui in Guyana. We also describe the previously unknown vocalization and breeding ecology of the species, and conducted an exploratory molecular analysis of the phylogenetic relationships within the genus Pristimantis represented by the members of the “unistrigatus species group” in the Guiana Shield. Pristimantis marmoratus is a small-sized species mainly distinguished from its known Guiana Shield congeners by the combination of F I < II, SVL ≤ 20.4 in males, presence of vocal slits in males, granular/pustulate dorsal skin with well-developed scapular ridges, basal webbing between fingers, fringes on fingers and toes, crossed iris, diffuse yellow or pale green wash on groin, and absence of flashy colour on axillary/pre-axillary region. The advertisement call consists of a single note repeated at a rate of ca 11 calls/min with a dominant frequency ranging from 2756 to 3101 Hz. Pristimantis marmoratus is primarily arboreal, exclusively active at dusk, and probably restricted to the pristine rainforests of the Pantepui uplands and highlands, east of the Gran Sabana between ca 600 and 1800 m above sea level. Preliminary molecular analyses recovered Pristimantis marmoratus as sister to an unnamed species from the Eastern Guiana Shield. On grounds of the newly established distributional extent we suggest maintaining the IUCN conservation status as Least Concern.

Aim Using the Pantepui palaeoendemic toad genus Oreophrynella, we explored (1) the origin of Pantepui endemism and the hypothesis of Pantepui being a source of diversity for the surrounding areas, including the geologically younger Andes; (2) whether early diversification of Oreophrynella conforms with that of Stefania (Hemiphractidae), another Pantepui endemic amphibian, which was recently shown to have vicariantly diverged from Pantepui highlands widespread Oligocene ancestors. Location The fractured island-like topography of the Pantepui biogeographical region in north-eastern South America. Methods We inferred the molecular phylogeny of Oreophrynella and other “basal” Bufonidae genera using three mitochondrial and two nuclear DNA sequences under Bayesian and maximum likelihood methods. We estimated divergence times using a relaxed-clock model and reconstructed ancestral areas through multiple models in a common likelihood framework. Results Phylogenetic analyses recovered a monophyletic Oreophrynella sister to Atelopus. Biogeographical analyses strongly suggested colonization of Pantepui via a pre-Miocene (Eocene/Oligocene) long-distance dispersal of a proto-Andean ancestor, followed by pre-Quaternary (lower Miocene) vicariant divergences of main lineages, and endemism of these main lineages to distinct biogeographical subunits. Main conclusions Our results suggest that at least part of the Pantepui diversity stemmed from dispersals from the proto-Andes. Three hypotheses emerge for the origin and evolution of Pantepui endemism, the Distance Dispersal theory, the Plateau theory and the Disturbance–Vicariance theory. Our results indicate that the early diversification of Oreophrynella conforms to that of Stefania, but hint at different factors responsible for the survival or extinction of different tepui summit amphibians.