Retained as a species by Goldman (1918) until Hall (1960) considered it only subspecifically distinct from O. palustris. Benson and Gehlbach (1979) returned O. couesi to specific status based on morphological contrasts with O. p. texensis in supposed area of intergradation; protein electrophoresis corroborates their lack of hybridization and genetic distinctiveness in sympatry (Schmidt and Engstrom, 1994). Karyotype reported by Benson and Gehlbach (1979) and Haiduk et al. (1979); morphometric comparisons with O. palustris by Humphrey and Setzer (1989). Alvarez-Castañeda (1994) discussed the indigenous status and possible extinction of the population (peninsulae) isolated near the tip of Baja California.

Following Hall’s (1960) example, other insular or localized subspecies—namely, antillarum, azuerensis, cozumelae, fulgens, gatunensis, and peninsulae (see Handley, 1966a; Hershkovitz, 1971; Jones and Lawlor, 1965)—were swept under O. palustris; they are here included in O. couesi because of geographic proximity. A composite of at least three species, the Mesoamerican populations referred to "couesi," as well as O. dimidiatus and O. gorgasi, should be critically reviewed (also see Sánchez et al., 2001).