Microleo is the smallest known thylacoleonid, being only the size of a Grey squirrel (Sciurus carolinensis).

    Microleo attenboroughi:

M. attenboroughi, named for British naturalist David Attenborough, is currently known only from a palatal fragment containing an incomplete row of teeth, from the Early Miocene of the Riversleigh World Heritage Site, Queensland.  The anatomy of Microleo suggests it is the most primitive of all thylacoleonids, and that the family as a whole are basal vombatomorphs that form the sister taxon of all other Vombatomorphia.

. Palatal fragment of Microleo attenboroughi. View a comparison with that of Thylacoleo carnifex.

    Priscileo:
    Late Oligocene - Middle Miocene

    Members of the genus Priscileo are small thylacoleonids about the size of a possum or cuscus.  The genus is currently represented by two species.

    Priscileo pitakantensis:

    P. pitakantensis known only from a rather poorly preserved fossil maxillary fragment and a few post-cranial bones recently found in the Late Oligocene Ngapakaldi Local Fauna at Lake Pitakanta in northeastern South Australia.

    Priscileo roskellyae:

    From the Early Miocene of the Riversleigh World Heritage Site, P. roskellyae is known from a complete skull and most of the dentition.