Species
Macrogonus
What a macrogonus looks like, what the name is, and how San Pedro and peruvianus relate to it.
What it looks like
It is reportedly bluish green, with about seven to nine low, rounded ribs and large areoles.
The name
The International Plant Names Index records Trichocereus macrogonus Riccob. as a validly published name, first published in 1909. Cereus macrogonus Salm-Dyck is reportedly the type species of Trichocereus — the name the genus itself is anchored to, designated by Britton and Rose in 1920. Reportedly, the treatment now in use keeps Trichocereus as a genus of its own rather than folding it into Echinopsis.
What the 2012 revision did
Reportedly a 2012 revision reads Salm-Dyck's original description of Cereus macrogonus as the plant later named Trichocereus peruvianus, and fixes the identity by designating a neotype.
The varieties, and when they were published
Trichocereus macrogonus var. pachanoi was reportedly published by Albesiano and Kiesling in 2012, and var. peruvianus by Lode in the same year.
Which name to use
Macrogonus, pachanoi and peruvianus are all still in everyday use among growers.
Where it grows wild
It has reportedly been collected in the wild in Bolivia and Peru.
Wild plants, not pot plants
Where a species grows wild says nothing about which plant is in anybody's pot.
Names in the library
A clone name is not proof of a species, and a photograph is a pointer rather than an answer.