Didolodus

Didolodus is an extinct genus of mammals from Middle Eocene Argentina. It is an ungulate mammal of uncertain affinities, possibly related to Litopterna, though this is uncertain due to the lack of reliable post-cranial remains, and for now remains Meridiungulata "incertae sedis". Its remains were found in the Sarmiento Formation of Patagonia.
"Didolodus" probably was a quick-footed creature which probably lived like early ungulates such as "Propalaeotherium", based on its highly similar teeth. It was around in length, with short limbs and a long tail.
Phylogeny.
Cladogram after Gelfo and Sigé, 2011: