Cy`a*tho*phyl"loid (s?`?-th?-f?l"loid), a. [NL. cyathophyllum, fr. Gr. ky`aqos a cup + fy`llon a leaf.] (Paleon.) Like, or pertaining to, the family Cyathophyllidæ.

Cy`a*tho*phyl"loid, n. (Paleon.) A fossil coral of the family Cyathophyllidæ; sometimes extended to fossil corals of other related families belonging to the group Rugosa; -- also called cup corals. Thay are found in paleozoic rocks.