A saucerful of secrets: comparative osteology of the genus Copeoglossum Tschudi, 1845 (Squamata: Scincidae) reveals a new species from Central Brazil

Abstract

The genus Copeoglossum is widely distributed throughout much of the Amazon basin and other regions of central, northern, and eastern South America, including Brazil, Bolivia, Colombia, Ecuador, Peru, Venezuela, Guyana, French Guiana, and Suriname. It also occurs in the Lesser Antilles (Redonda, St. Vincent, the Grenadines, Grenada, Trinidad and Tobago). Despite the recent increase in molecular and taxonomic studies on Neotropical skinks, populations of Copeoglossum in northern and eastern South America remain understudied. Here, we examined 380 specimens from 64 localities, representing all currently recognized taxa of the genus Copeoglossum. Specimen preparation included dry skull, clearing and staining, X-ray, and high-resolution computed tomography (μCT). This study provides a detailed anatomical reference for the adult skull of species in the genus Copeoglossum, emphasizing osteological features that may aid in delineating robust species boundaries. Our findings support the recognition of a distinct lineage that does not currently have a formal name (though it has been previously identified in other studies), which we describe herein as a new species based on both cranial osteology and external morphology, as well as molecular evidence. This newly recognized species appears to be endemic to the Cerrado ecoregion, also occurring in transitional areas of Brazil's central-western region.