See text Cassianellidae is a small extinct family of prehistoric bivalves which lived from the Middle Triassic, Ladinian stage through the Late Triassic Norian stage.

Living a stationary life attached to substrate in marine and brackish environments, they formed shells of an aragonite composition with a low amount of magnesium calcite.

They are thought to have a close relationship to the longer lived family Bakevelliidae and it is possible the cassianellids may have even evolved from one of the early Triassic bakevelliid genera.

Only a few modern families, such as Gryphaeidae, still retain the alivincular-areate ligament system.

[1] In contrast, Lilangina is known only from Asia, and Septihoernesia from the middle Triassic of northern Italy.