Isectolophus scotti (Scott and Osborn 1887; Holbrook, Lucas and Emry 2004; Early Oligocene to Early Miocene) nests basal to the Arsinoitherium clade in the LRT.

Periptychus carinidens (Cope 1881; Shelley et al. 2018) was originally and later unable to determine closest relatives. Here it nests between tiny Monodelphis and horned Arsinoitherium. The manus and pes are primitive in having no reduced fingers or toes, yet the unguals are reduced to stub-like round hooves.

Bemalambda nanhsiungensis (Chow et al 1973; Li 2005; early to middle Paleocene 60mya, China, 1m in length) was originally considered a pantodont. Here it isclose to Periptychius at the base of the Uintatherium clade. Note the clavicles. Seems to be an herbivore with those hooves and small dentition.

Bemalambda pachyoesteus is the middle image specimen. The left and right feet are interchanged on this mount.

Orthaspidotherium edwardsi (Ladeveze et al. 2010; Late Paleocene, 58 mya, 7.5cm skull length) nests with Meniscotherium. The skull is twice as wide as tall on this weasel-like terrestrial mammal. The jawline is convex at the canine and beneath the orbit. The lacrimal/jugal/zygomatic arch is quite robust.

Pholidocercus hassiacus (von Koenigswald & Storch 1983; HLMD Me 7577; Middle Eocene) is an ancestor to the larger, later Arsinoitherium. Known from several fossils, Pholidocercus has a long thick tail provided with tall neural spines and deep chevrons. The rostrum is short. Soft tissue is preserved as scales on the head in a helmet-like formation and scales on the tail, a pattern convergent with armadillos.

Arsinoitherium zitteli (Beadnell 1902, Figs. 1, 2; late Eocene, early Oligocene, 36-30 mya) was a sister to Gobiatherium and derived from a sister to Meniscotherium. Wikipedia describes Arsinoitherium as, "an extinct genus of paenungulate mammal belonging to the extinct order Embrithopoda. It is related to elephants, sirenians, hyraxes and the extinct desmostylians."

A trait that makes Arsinoitherium distinct is its nearly complete arcade of teeth, none of them tusks, 3 molars and the medial incisor is missing. The premaxilla redevelops an ascending process of the premaxilla, a trait not seen in mammals since their origin in the Triassic.