Moreno's rival, Florentino Ameghino, also found fossils of Brontornis which he named Brontornis platyonyx in 1895 based on four pedal phalanges found at Monte Leon. The species has been synonymized with Brontornis. Ameghino also named Liornis floweri based on a distal tibiotarsus, distal tarsometatarsus, and two pedal phalanges of a juvenile that was synonymized with Brontornis in 1967.Buffetaut, E. (2016). A reassessment of the giant birds Liornis floweri Ameghino, 1895 and Callornis giganteus Ameghino, 1895, from the Santacrucian (late Early Miocene) of Argentina. Palaeovertebrata, 40, e3. Liornis minor was also synonymized in 1967, but it has since been synonymized with Phorusrhacos. Callornis giganteus, another Ameghino taxon, may also be a synonym of Brontornis or a distinct close relative. Recently, the affinities of some Brontornis specimens has come into question due to the uncertain and debated phylogenetic position of the genus and its synonyms.
