The snakes Chironius scurrulus (Schlegel, 1837) and Dendrophidion dendrophis (Wagler, 1830) are widely distributed in northern South America, having great systematic complication and lack of morpho-anatomical knowledge. The present work aims to recharacterize the species with the inclusion of new characters, thus contributing to a better knowledge of the Neotropical ophiophilous biodiversity. All specimens deposited in the Museu Paraense Emílio Goeldi Herpetological Collection (75 of D. dendrophis and 41 of C. scurrulus) were analyzed, extracting 11 meristic and 17 external morphometric data from each specimen. Osteological (synchrons, n=6) and hemipenial (male genitalia, n=6) preparations were made. The following results were obtained: (A) Scutellation (scales and shields): C. scurrulus with ventrals (VE) ranging from 142-161 (n=41), female: 142-158 (n=12), male: 147-161 (n=29); and subcaudals (SC) ranging from 142-161 (n=41), female: 72-158 (n=10), male: 78-128 (n=19); D. dendrophis with VE = 142-161 (n=75), female: 144-163 (n=29), male: 124-160 (n=46) and se: 142-161 (n=52), female: 144-208 (n=20), male: 127-197 (n=32). Osteometry revealed significant differences in the following length ratios: (1) parietal/ skull, (2) frontal/ skull, (3) pterygoid/ skull, (4) maxillary/ skull, (5) compound/ skull, (6) hemimandibula/ skull, (7) dorsal aspect of dentary/ skull, (8) square/ skull and (9) parietal width/ skull length. From the prepared hemipennis one has: C. scurrulus has organ with the hemipenial synapomorphy of the genus, i.e., the presence of a pouch on the hemipenial peduncle. The heemipennis of D. dendrophis is described for the first time and reveals the absence of the synapomorphy considered for the subfamily it is currently allocated to. The data obtained substantially change the specific descriptions and contribute to the foundation of future phylogenetic analyses that encompass the species analyzed.
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