An update on the amphibian assemblage of the Ukaguru Mountains, Tanzania, with the description of a new giant <i>Arthroleptis</i> species (Amphibia: Anura)

Effective conservation measures require accurate and complete species inventories, which are however often missing for particularly biodiverse regions of concern. The montane forests of the Eastern Arc Mountains (EAM) in East Africa represent fragmented relics of unique habitats that harbour remarkable levels of plant and animal diversity, including many endemic and threatened species most of which are poorly known. The present study focuses on the Ukaguru Mountains, an important mountain block in the central EAM, and expands on a recent study that summarized data from 30 years of amphibian surveys. Using systematic sampling (2022–2024) in localities that are less heavily impacted by anthropogenic activities than previously surveyed sites, we increase the number of documented amphibian species from 17 to 19, adding Xenopus cf. victorianus and a newly described species (see below). Among the three Ukaguru-endemic toads which have not been recorded since more than two decades, we re-discovered Nectophrynoides laticeps and N. paulae but failed to record the enigmatic Churamiti maridadi, which according to a dedicated extinction model has an updated probability of only 47.6% of still being extant. Based on genetic, morphological and bioacoustic evidence, we also describe a new large-bodied species of Arthroleptis (Arthroleptis mamiwakisaraensis sp. nov.), shedding further light into the evolution of ‘giant’ congeners which inhabit other mountain blocks in the EAM. Given the rapid deforestation of the EAM for which the Ukagurus are no exception, our findings give rise to concerns regarding current and future extinction risks within unique mountain amphibian assemblages, also affecting species which potentially still await description. http://zoobank.org/urn:lsid:zoobank.org:pub:04EC6DEE-D2D9-463D-B8AB-18560AC2AB85