Members of the group were small-medium sized cursorial herbivores with brachydont teeth, with their toes showing progressive reduction, with later members of the group bearing weight on a single large toe similar to living horses.

However, fossils found in Argentina, Brazil and Uruguay show that one member of the group, Neolicaphrium recens survived into the Late Pleistocene.

Anisolambdinae (also called Anisolambdidae in some studies) was proposed to unite the primitive and earlier forms Anisolambda, Eolicaphrium, Paranisolambda, Protheosodon, Guilielmofloweria, Heteroglyphis, Lambdaconops, Wainka and Xesmodon.

[6] Proterotheriidae was redefined by McGrath and colleagues in 2019 to be all taxa closer to Tetramerorhinus than Macrauchenia, Tricoelodus or Protolipterna.

[5] The cladogram below shows the modified results of their phylogenetic analysis, where incomplete taxa were placed based on morphology.