The genus Henricosbornia was first described in 1901 by Florentino Ameghino, based on fossil remains found in terrains dating from the Early Eocene of Argentina, in the Chubut Province. In a few years, Ameghino described numerous remains of teeth from the same area and considered them as belonging to various species of notoungulates, which he named Hericosbornia lophodonta (the type species), Hemistylops paucicuspidatus, Hemistylops trigonostyloides, Pantostylops completus, Microstylops monoconus, Prohyracotherium patagonicum, Microstylops clarus, Selenoconus spiculatus, Prohyracotherium matutinum. The generic name is derived from the famous paleontologist Henry Fairfield Osborn. All these species were later identified as Henricosbornia lophodonta by George Gaylord Simpson, who identified the numerous dental remains as intraspecific variations.[1]
Several other species were attributed to the genus, some of them still considered valid; Henricosbornia ampla, the youngest species, was found in deposits dating to the Middle Eocene as well as H. minuta. One of the species described by Ameghino in 1901, Pantostylops typus, may have been a distinct species of Henricosbornia. Fossils attributed to the genus were also discovered in slightly more ancient, Late Paleocene terrains of Argentina.[2]
Given its archaic characteristics, Henricosbornia is considered to be one of the most basal notoungulates. It is the eponymous genus of Henricosborniidae, a family including the most basal notoungulates, and classically associated with the Notostylopidae within the probably paraphyletic suborder Notioprogonia. It is related to Nanolophodon.
