Taxonomic revision of Pituophis stems mostly from genetic work by J.A. Rodriguez-Robles and J.M. De Jesus-Escobar, published in 2000 [Molecular Phylogenetics and Evolution 14(1):35-50]). Previously, gopher, bull-, and pine snakes were considered one species, P. melanoleucus. Now, gopher and bullsnakes are elevated to species status as P. catenifer and the Louisiana Pine Snake is also regarded as a distinct species.