Paracyathus caryophyllus was a solitary stony coral whose single polyp secreted a cup-like aragonitic skeleton. The living polyp extended tentacles above the calice to capture plankton and suspended organic particles, retracting into the skeletal cup when disturbed.

It was not a reef-building colonial coral. In the fine-grained London Clay setting, a solitary, non-reef and probably azooxanthellate ecology is the most reasonable comparison with related caryophylliids. Fossils are known from the corallum, whose septa and wall record the architecture of the living polyp.