Enalloporidae, Sphragioporidae, Thamniscidae Miller, 1889, Fenestrellinidae Bassler, 1935[1] Fenestellidae is a family of bryozoans belonging to the order Fenestrida.
The skeleton of its colonies consists of stiff branches that are interconnected by narrower crossbars (or dissepiments).
The front of the branches carries small nodes in a row or zigzag line between the apertures.
Branches split (or bifurcate) from time to time giving the colonies a fan-shape or, in the genus Archimedes, create an mesh in the shape of an Archimedes screw.
[1] Like all bryozoans, Fenestellids were epifaunal suspension feeders, that occurred between the early Ordovician and the Triassic.