What is "reigitherium"

Reigitherium bunodontum is a mammal that lived during the Late Cretaceous (Late Campanian- Maastrichtian). Fossils of it have been found in the Los Alamitos and the La Colonia Formations of Argentina.

Reigitherium was initially classified in the order Dryolestida. In 2000 Pascual et al. found it to be a Docodont. Later authors found it to be neither a dryolestoid nor a docodont, and found it to be of uncertain placement within Mammalia. In 2011, Rougier et al. found it to be a Dryolestoid again, within Meridiolestida, a clade composed of Gondwanan Dryolestoids. It "differs from other Mesozoic mammals including docodontans in that the lower molars decrease in length and notably increase in width posteriorly."