Ilariids are thought to be the largest marsupials of their time in the Lake Eyre and Tarkarooloo basin, and lived along with Wynyardiidae, Obdurodon, and thylacoleonids (marsupial lions) such as Priscileo and Wakaleo.
Page 237 includes: "In Steropodon, the mandibular canal suggests the presence of a bill, with a bill also known in Obdurodon dicksoni and Ornithorhynchus anatinus."