Cranial adaptations for feeding on snails in species of Sibynomorphus (Dipsadidae: Dipsadinae)

•The shape of the skull and mandible in three species of goo-eating snakes of the Neotropical genus Sibynomorphus is analyzed.•Geometric morphometric tools are used to assess morphological adaptations related to slug- and snail-feeding in that genus.•The examined species have osteological specializations for the mechanical extraction of soft-bodied mollusks. Neotropical “goo-eating” dipsadine snakes display a set of morphological and histo-chemical adaptations linked to the capture of their soft-bodied, viscous invertebrate prey. Within this group, species from the genus Sibynomorphus feed chiefly on snails and slugs. Here, we analyzed a series of skull and mandible characters in S. mikanii, S. neuwiedi and S. turgidus using geometric morphometrics, with the aim of assessing morphological adaptations related to slug- and snail-feeding in that genus. We further compared the results with Leptodeira annulata, a species that feeds on vertebrates. To evaluate shape differences of the skull and mandible between species we performed a multivariate analysis of variance and a linear discriminant analysis. Our results show that the narrow, elongate skull in S. mikanii may help with slug ingestion, while asymmetry in teeth number and mandibular shape in S. neuwiedi and S. turgidus are likely related to snail feeding.