[1] It is a meridiolestidan, closely related to the also Late Cretaceous Cronopio and the Miocene Necrolestes.

[2][3] Leonardus is a fairly small mammal, similar in size to Necrolestes.

The genus name honours the Italian paleontologist Giuseppe Leonardi.

Leonardus was originally referred to Dryolestidae, but the lack of a parastylar hook on the molariforms, as well as a few features of the stylocone, suggest that it was grouped with other South American and African species at the exclusion of Laurasian species, in a clade known as Meridiolestida.

[2][3] Leonardus' teeth are noted as being unique among meridiolestids and the animal would have had an orthal and transverse jaw-stroke with tooth-to-tooth shearing,[4] though no further comments have been made on its diet.