Biology

Pentacrinites fossilis lived attached to driftwood.

The animal has a crown of arms which it uses to catch plankton that is held in the water column and away from the driftwood by a stem. The arms bear numerous rows of pinnules from which mucus covered tube feet extend and catch plankton.

Food particles are passed down the arms and into the mouth at the arm bases and ontop of the body or calyx of the crinoid.

The stem of the crinoid is covered in mobile finger like extentions called cirri. The cirri of Pentacrinites fossilis is so dense that it appears almost hair like. These cirri however functioned to attach the crinoid to the driftwood and also to other individual crinoids attached to the driftwood.

Size

Individuals can reach up to 2 metres in length.

Growth

It is though that Pentacrinites fossilis grew rapidly as driftwood tends to become water logged after several months or years.

Lifecycle

Similar for other crinoids where fertilised embryos are released and attach to a hard substrate before changing into a free swimming larvae. The larvae then attach to an appropriate substrate; driftwood and grow into an adult.