Forstercooperia possesses a small post-insicor diastema, not as large as its descendants, and similar in size to that of Hyracodon.

Material of many different genera as well have been at some time included in Forstercooperia, such as that of Juxia[1] and Uintaceras[4] In 1923, a mostly complete skull of an early rhinoceros relative was unearthed.

[4] It is also the senior synonym of F. shiwopuensis, a species named in 1974 by Chow et al..[1][8] In 1963, material including a partial skull containing cheek teeth was unearthed in Late Eocene deposits of Mongolia.

These remains were identified as from a true rhinoceros by Wood, who found them an important discovery with the scant amount of previous cranial material of early rhinocerotids available.

The binomial created was Pappaceras confluens, classified as a close relative of Forstercooperia within Forstercooperiinae (before Forstercooperiidae, named in 1940 by Kretzoi).

[9] In the 1960s, newly uncovered material from the Irdin Manha Formation was identified as belonging to a new species of rhinocerotoid.

However, Holbrook and Lucas identified that the only North American material of F. minuta, F:AM 99662, had no features justifying its inclusion with the species, and reassigned it to their new binomial, Uintaceras radinskyi.

The authors noted that it was from the same region and in the same size range as F. totadentata, which Lucas et al. (1981) found it to tentatively represent.

Unlike Radinsky, their paper found Juxia to be separate, with F. borissiaki inside the genus, and F. grandis to be a definite species.

[8] In the most recent review of the genus, focusing on the North American material, it was found that some earlier conclusions were no longer valid.

This paper, published in 1997 by Luke Holbrook and Lucas, named a new genus, Uintaceras for all the North American material of Forstercooperia.

Holbrook and Lucas named a new species, U. radinskyi, assigning the North American material of Fostercooperia to it.

[2] The subfamily Forstercooperiinae, to which Forstercooperia belongs, is considered part of Paraceratheriidae, a group containing the largest land mammals ever to walk the earth.

He performed a phylogenetic analysis which placed Uintaceras, then amynodontids, then Paraceratherium, then Juxia and Forstercooperia, and finally hyracodontids as the successive outgroups of Rhinocerotidae within Rhinocerotoidea.

[12] Later cladistic analysis confirmed some conclusions of Holbrook (1999), recovering hyracodontids as the basalmost rhinocerotoids and paraceratheres as closely related to Eggysodontidae and crown rhinos.

Most important remains are from the Middle to Late Eocene Irdin Manha Formation of Inner Mongolia (China).