Fossils of this group have been found in Asia, Africa, North America and Europe.

Hyainailourids are characterized by long skulls, slender jaws, slim bodies, and a plantigrade stance.

The anatomy of their skulls show that they had a particularly acute sense of smell, while their teeth were adapted for shearing, rather than crushing.

[citation needed] Only Simbakubwa, Megistotherium and several of its sister genera, including Hyainailouros and Sivapterodon, survived into the Miocene.

Hyainailouridae used to be considered a subfamily of Hyaenodontidae, but cladistic study by Sole et al., (2013, 2015) treats it as a distinct family.