Furcacaudidae, the "'fork-tailed' agnathans," is an extinct family of thelodontid agnathans from the Lochkovian stage of the Early Devonian epoch and Wenlockian epoch of the Silurian, known from fossils found in Northern Canada.

[1] A study in 2009 published by Wilson and Tiiu Märss moved members of Furcacaudiformes (and by extension Furcacaudidae) into a more basal position based on a more up-to-date data matrix, suggesting the divergence of Furcacaudidae from other thelodonts occurred earlier than previously theorized.

The following is a portion of the 2009 revised cladogram, demonstrating Furcacaudidae's position in relation to the order Furcacaudiformes.

Its discovery and analysis gave rise to Wilson's and Caldwell's theory that stomachs evolved before jaws, based on sediment infillings found in fossils of F. heintzae.

Its body was hunched and pomacanthid-esque, almost resembling modern marine angelfish in its qualities.