Molecular and morphological insights into the taxonomy and distribution of the Amazonian snake Erythrolamprus carajasensis (Cunha, Nascimento & Ávila Pires, 1985) (Serpentes, Xenodontinae)

Erythrolamprus carajasensis was originally described from the canga areas of the Carajás region in the state of Pará, Brazil, and its distribution is restricted to the type locality. The species exhibits morphological similarities to E. almadensis , which has a parapatric distribution. In this study, we investigated the taxonomic status of E. carajasensis using both molecular and morphological data. We generated mitochondrial gene sequences (12S rRNA and 16S rRNA) for three specimens of E. carajasensis and 11 specimens of E. almadensis and compared them with sequences available in GenBank for Bayesian phylogenetic inference. We examined specimens of E. carajasensis , including its type series, and compared them with morphologically related and congeneric taxa. Our analysis included meristic and morphometric characters, color patterns, hemipenis and cranial osteology. Our integrative approach thus supports the recognition of E. carajasensis as a distinct evolutionary lineage from E. almadensis , despite their morphological conservatism in some characters. The skull differences observed, which are congruent with the molecular phylogeny and geographic distribution, justify the redefinition of E. carajasensis to include Amazonian populations formerly attributed to E. almadensis . In contrast, E. almadensis is now restricted to extra-Amazonian populations in Brazil, primarily those occurring in the Atlantic Forest, Cerrado, and ecotonal regions with the Caatinga, in eastern and southern Brazil. The geographic separation between E. almadensis and E. carajasensis is primarily delineated by the Amazon–Tocantins interfluve, reflecting ecological and possibly historical barriers to dispersal.