A new species of Epicrionops (Amphibia: Gymnophiona: Rhinatrematidae) from Ecuador, with integrative morphological and phylogenetic insights into Ecuadorian Epicrionops Boulenger, 1883 and Amazops Wilkinson, Reynolds & Jacobs, 2021

The Neotropical tailed caecilians of the genera Epicrionops and Amazops (Rhinatrematidae) remain poorly known. Here, we examined their morphology, distribution, and molecular phylogenetic relationships using specimens from Ecuador. Our review of museum collections expands the empirical basis for understanding variation in these genera and reveals broader geographic and morphological diversity than previously recognised. Morphological and µCT-based analyses identified consistent diagnostic differences between Amazops and Epicrionops , particularly in annular counts and cranial bone configurations. We describe a new species of Epicrionops from the montane forests of southeastern Ecuador, characterized by a relatively small body size in fully metamorphosed individuals (174–317 mm); a maxillopalatine enclosing the orbit; a long spatulate posterodorsal process of the squamosal; an articular facet of the quadrate contacting the posterior end of the maxillopalatine but not the squamosal; a retroarticular process of the pseudoangular that is dorsally concave and ventrally convex; frontals with slightly notched anterior and posterior margins and curved lateral edges; and an os basale with a narrowing cultriform process and wavy, rounded margins. The pterygoid is large, attached to the maxillopalatine, and barely contacts the quadrate. Phylogenetic analyses of mitochondrial genes (12S, 16S, ND1) recovered the new species in a clade with E. marmoratus - bicolor , the only congeners for which molecular data are currently available. We report, for the first time, the phylogenetic position of the genus Amazops and also expand the known distribution of Amazops amazops . Our molecular data suggest that the genus is more diverse than currently recognized, identifying additional potentially undescribed species. These findings provide new integrative evidence on the morphological and phylogenetic diversity of Rhinatrematidae and highlight the need for broader sampling and integrative analyses in the tropical Andes.