Family Terebrataliidae Cooper, 1973

Large shells (up to 46 mm in length) rectimarginate or sulcate, with smooth or ribbed surface. Dental plates can be changed with thickened bases in old specimens. Cardinal process is big, inner and outer hinge-plates are absent. Brachial loop in adults keeps weak connection between descending branches and middle septum (as in Terebratalia) or loses this connection (as inCoptothyris).

The family includes two genera and three species distributed near Asiatic coast of the Northern Pacific.

Key to genera of the family Terebrataliidae

1(2). Shells are with well expressed radial ribs, which are triangular in section. Ribbon of brachial skeleton loses its connection with middle septum in adults completely Coptothyris

2(1). Shells are smooth or with concentric lines of growth. Descending branches keep connection with middle septum during all life, sometimes this connection looks like a thread or like a dotted line in soft tissue of adults Terebratalia