Petalocrinus

Petalocrinus is a genus of primarily Silurian cladid cyathocrininid sea lily of the superfamily Gasterocomacea.

Fossils of the numerous species have been found in Silurian strata in North America, England, Sweden, and China, where they underwent a speciation event during the early Late Silurian that gave rise to Sinopetalocrinus and Spirocrinus

As with all other members of Petalocrinidae, the five arms of Petalocrinus were fused into flower petal-shaped (or guitar pick- or button-shaped) wedges, with a distinctive pattern of grooves. It is assumed that the grooves played a role in conveying food, i.e., plankton captured by the tubefeet, to the mouth. The function of the arms, on the other hand, is a source of much speculation.