Roux, M. & Lambert, P. (2011)

Two new species of stalked crinoids from the northeastern Pacific in the genera Gephyrocrinus and Ptilocrinus (Echinodermata, Crinoidea, Hyocrinidae). Effects of ontogeny and variability on hyocrinid taxonomy

. Zootaxa, 2825 (1), 1–54.