Columnar branches and pale bands
Historical descriptions of both forms report long ribbed stems and areoles with distinct spines. Paler bands on the green surface mark the beginnings of successive growth increments. Flowers are substantially larger than those of Myrtillocactus, and the fruit pulp in the Costa Rican account of Lemaireocereus aragonii is white. Large black seeds are useful when comparing flowering and fruiting plants. [Britton and Rose 1920]
Relationships and nomenclatural changes
A study of five chloroplast markers placed Marshallocereus in a group also including Carnegiea, Lophocereus, Nyctocereus and Pachycereus. The published abstract describes this group as sister to Peniocereus. Current nomenclature connects historical accounts of plants assigned to several genera with one modern species record. [Franco-Estrada et al. 2021] [2-WWW]
Distribution
The genus extends from southeastern Mexico into Central America. The M. aragonii account describes plant variation across this area and the scope of historical names. [2-WWW]