Taxonomia de Epictia vellardi (Laurent, 1984) (Leptotyphlopidae, Serpentes) com base em dados de morfologia externa e interna

Abstract

'Scolecophidia' are snakes characterized by their small size, commonly known as blind snakes, worm snakes, or thread snakes, exhibiting various adaptations associated with fossorial and semifossorial lifestyles. Given the importance of internal and external morphology studies of Leptotyphlopidae representatives, especially in their delimitation and generic allocation, a refined quantitative and qualitative study is necessary to contribute not only taxonomic information but also insights into potential ontogenetic or sexual variation within this family. This study aimed to conduct a taxonomic review and redescribe Epictia vellardi, presenting detailed data for the first time on its external and internal morphology, including skull description, atlas and axis, pelvic girdle, cranial and post-cranial cartilaginous elements, as well as intra-specific variations. Laurent's original description (1984) had weaknesses warranting a redescriptive effort, primarily due to limited sampling of the holotype and a paratype, succinct morphological data, and outdated methodology. Additionally, considering the species' placement in Epictia based on a phylogenetic hypothesis from exclusively molecular data, external and internal morphology data were crucial to complement molecular analyses, enhancing our understanding of its systematics. The study presented the largest sample size ever recorded for scolecophidians, including males and females, revealing no sexual dimorphism. Scolecophidia are generally undersampled, leading to the belief that they are rare. However, the study found a high population density of snakes in the urban region of Corumbá (MS), suggesting that their perceived rarity is more due to sampling biases than actual scarcity. The research provides new records for Anastácio, Aquidauana, and Ladário (MS). The absence of records in Brazil, Paraguay, and Argentina may reflect sampling gaps, common also among other snake species inhabiting the region. We confirm the correct placement of E. vellardi in the genus due to the non-participation of the basioccipital in the formation of the foramen magnum and the presence of paired nasals and supraoccipitals. E. vellardi showed the absence of intercentrum I in the atlas, a characteristic also observed in other species of the genus, although the dorsal region of the vertebra is not fused. This pattern had not been described in Epictia before and may be associated with the phenomenon of miniaturization. The information from this study could contribute to the recognition of Leptotyphlopidae taxa.