Relationships between Numbers of Vertebrae, Scale Counts, and Body Size, with Implications for Taxonomy in Nightsnakes (Genus:Hypsiglena)

Abstract

Abstract The relationships between the number of trunk and caudal vertebrae, the number of ventral and subcaudal scales, and snout–vent length (SVL) and tail length were investigated in several species of Hypsiglena, including a few specimens from species contact zones. We confirm the presence of a 1:1 relationship between trunk vertebrae and ventral scales within Hypsiglena (99 specimens total; 50 males; 49 females). We also found a positive relationship between the number of ventral scales and SVL in adult specimens. We did not find a 1:1 relationship between caudal vertebrae and subcaudal scales, but there is a positive relationship between subcaudal scales and tail length. Because there is a positive relationship with the number of ventral scales and SVL, we infer—as general population trends—that snakes with more ventral scales have the capacity to grow to be larger than snakes with fewer ventral scales. Many other environmental factors influence body size, however, and this trend should be used only...