Whaitsiidae

Whaitsiidae is an extinct family of therocephalian therapsids. Whaitsiids were among the most diverse therocephalians of the Late Permian, though they would go extinct at the end-Permian mass extinction.

== Description == thumb|left|Restoration of Moschowhaitsia|Moschowhaitsia vjuschkovi Whaitsiids and their closest relatives (hofmeyriids and Ophidostoma) are grouped together in the clade Whaitsioidea. Some of their distinctive traits include a reduced number of postcanine teeth, a broad skull, and a boomerang-shaped lower jaw. At the front, the lower jaws have a loose rather than solid connection at the symphysis (chin), while at their rear the jaw joint is streptostylic. This would have given whaitsioids an unusually wide and flexible gape among therapsids, not dissimilar to snakes.