We investigated the morphology and distribution of Pituophis deppei (Duméril, Bibron & Duméril, 1854), Mexican populations of P .  catenifer (Blainville, 1835), and P . lineaticollis (Cope, 1861) from west of the Isthmus of Tehuantepec, examined the relevant and traceable type series of Mexican nominal taxa belonging to this species group, and appraised so far unattended contemporaneous documents related to the collector Ferdinand Deppe. Pituophis deppei and lineaticollis virtually coexist along the central Transvolcanic Belt and in the Puebla-Oaxaca-Veracruz border triangle (first state records for lineaticollis in Veracruz). The allegedly diagnostic neck pattern does not reliably distinguish deppei from lineaticollis in, for instance, Michoacán. Deppe’s bullsnake and the northern catenifer show largely parapatric ranges and are morphologically distinct. Supposed hybrids (catenifer × deppei) occur in a narrow sector across the Northern Plateau, and bullsnakes with in-between combinations of character states predominate along the Chihuahua-Sonora border north of the Sierra Tarahumara. Phenotypically intermediate specimens encompass part of the type series of P . mexicanus Duméril, Bibron & Duméril, 1854 (lectotype designation), a composite and long disused taxon including at least one original voucher akin to catenifer and one presumably from N Hidalgo (Huasteca). We recovered three syntypes of Elaphis pleurostictus Duméril, Bibron & Duméril, 1854 (syn. P . deppei) and unearthed a formerly neglected name-bearer of P . deppei pholidostictus Jan, 1863 (syn. P . lineaticollis). The study clarifies the origin of a limited number of Mexican amphibians and reptiles received from F. Deppe, re-establishes the type localities of E . [ Pituophis ] deppei, its simultaneous synonym E . pleurostictus D. B. & D., as well as the phrynosomatid lizard Sceloporus grammicus Wiegmann, 1828, and highlights resulting taxonomical complications. Also, it elucidates the origin of further zoological type material collected by this naturalist and addresses issues of nomenclatural relevance in the context of scientific names related to Deppe specimens.

Distribution, Ferdinand Deppe, morphology, Pituophis spp. (catenifer, deppei, lineaticollis), Sceloporus grammicus, species boundaries, systematics, type localities, type material