Seirocrinus subangularis was thought to breed once a year when both eggs and sperm are released into the water column.
Seirocrinus subangularis would have occurred as both male and female individuals.
Sperm is released into the water (spawning) and stimulates the eggs, held on the pinnules at the end of the arms of the female individuals. The resulting eggs are produced in large numbers and are fertilised almost immediately after release (see Lifecycle in the Biology section).
Via a zooplanktonic larval stage. However, this crinoid lived in areas where the seabed was anoxic. Thus, the larva would settle on vacant parts of the floating wood structure.