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The Guiana Shield harbours one of the best preserved and largest extents of tropical forest on Earth and an immense biodiversity. The herpetofauna of this region remains poorly known. The species-rich snake genus Atractus contains ∼140 species, many with complicated taxonomic histories, including A. schach. Examination of specimens in museums and newly collected material from French Guiana has allowed the illustration of hemipenial morphology for the first time and an expanded diagnosis. Concatenated molecular phylogenetic (mitochondrial and nuclear genes) and phenotypic (morphometrics, external and hemipenial morphology) analyses confirm non-monophyly of the A. flammigerus group and indicate that A. schach is a species complex with three new species described here. The geographic distribution of A. schach sensu stricto is restricted to Guiana, Surinam, and French Guiana north of Tumucumaque massif. Populations tentatively assigned to A. schach from the east from French Guiana in the Roura lowlands to Almeirim, and from central Amazonia between the Negro and Trombetas rivers in Brazil are also recognized as new species. Our results suggest that populations from south of the Amazon River are not conspecific with those from the Guiana Shield. [ABSTRACT FROM AUTHOR]

The systematics of Leptotyphlopidae is historically controversial mostly due to their conserved external morphology in comparison with other snakes. However, recent studies have stressed that anatomical data might be informative for clarifying the leptotyphlopid taxonomy and evolution. We erect a new genus to accommodate Leptotyphlops collaris based on evidence from osteology, hemipenial morphology, and molecular data. We also provide expanded data regarding the intraspecific variation based on additional specimens collected in field trips and literature data, performing detailed comparisons among the new genus and all other New World leptotyphlopids. The new genus is distinguished from other leptotyphlopids by its unique hemipenial morphology and its exclusive combination of osteological and external morphology characters, with molecular data also supporting the new generic arrangement. We also provide a comprehensive discussion of the hemipenial morphology for the subfamily Epictinae based on literature and novel data gathered herein. [ABSTRACT FROM AUTHOR]