It is important for biology students to understand how genetic variation is related to the formation of species in nature. This module is intended for students to obtain first hand experience with a real world case study of how researchers working with a widely distributed species of snake detected that two different species were present. Through a video lecture featuring researchers, some of whom were involved in the black-tailed rattlesnake split, students explore the rationale for the taxonomic decisions outlined in the project. Subsequently, students are guided through a series of analytical processes working with the data from the 2012 study that are derived from genetic, morphological, and geographical information.