Opuntia engelmannii Opuntia engelmannii Opuntia engelmannii is a prickly pear common across the south-central and Southwestern United States and northern Mexico. It goes by a variety of common names, including cow's tongue cactus, cow tongue prickly pear, desert prickly pear, discus prickly pear, Engelmann's prickly pear, and Texas prickly pear in the US, and nopal, abrojo, joconostle, and vela de coyote in Mexico. The nomenclatural history of this species is somewhat complicated due to the varieties, as well as its habit of hybridizing with "Opuntia phaeacantha". The "Opuntia engelmannii" range extends from California to Louisiana in the United States, and from Sonora
Opuntia readily between species. This can make classification difficult, yielding a reticulate phylogeny where different species come together in hybridization. Also, not all species listed here may actually belong in this genus, meaning that "Opuntia" is not a monophyletic group. "Opuntia" also has a tendency for polyploidy. The ancestral diploid state was 2n=22, but many species are hexaploid (6n = 66) or octaploid (8n = 88). Chollas, now recognized to belong to the distinct genus "Cylindropuntia", are distinguished by having cylindrical, rather than flattened, stem segments with large barbed spines. The stem joints of several species, notably the jumping cholla ("Cylindropuntia