Aceratherium incisivum (Kaup 1832; originally Rhinoceros incisivum, Cuvier 1822; Miocene; 2.3m long) nests between rhinos and brontotheres Aceratherium lacks an upper canine and premaxillary teeth.

Eotitanops (Osborn 1907; Early Eocene; 45 cm tall at the shoulder) is the earliest and most primitive titanothere (bronthothere). It ate leaves and had five-toed front legs and three-toed hind legs.

Lambdotherium popoagicum (Cope 1880, Mader 1998; Eocene, 50-46mya; ghosted out above) had been considered a stem brontothere, but here nests with the basal artiodactyl, Ancodus.

Embolotherium andrewsi (Osborn 1929; ) is currently a sister to the rhino, Ceratotherium (likely by convergence because both have smaller hornless ancestors) and both were derived from a sister to Hyrachyus.

The nasal was anteriorly elevanted into a paired horn. The naris may have been elevated along with the horn. The skull was 2x wider than tall at the orbits. The molars are much larger than the premolara, that are molarized. The canines were tiny. The posterior skull was greatly elevated. The dorsal spines were greatly elevated. The lumbar region was reduced. The ilia were transverse. This giant herbivore was probably like a bison in its niche.

Titanotherium (Megcerops) coloradensis (Leidy 1870; Late Eocene, 38-33mya; 2.5m tall at the shoulder, 5m i nlength)

Megacerops includes the species of the genera Menodus, Brontotherium, Brontops, Menops, Ateleodon, and Oreinotherium.