Diamond-backed watersnake

This heavy-bodied snake has dorsal diamond-shaped light brown blotches separated by thin dark brown bands that form a chain-like pattern. The rectangular lateral blotch has two thinner lines (making a Y) that connect to adjacent dorsal blotches. This is especially obvious in the juvenile. The scales are heavily keeled mid-dorsally. The yellow belly may have half-moon marks on it, the largest of which are concentrated near the sides. There is a divided anal plate and a double row of scales under the tail. Males have raised bumps on the chin, which are used for courtship. (information from "A Field Guide to Amphibians and Reptiles of Oklahoma")