Doweld, Alexander B. “Protaeropsis, a New Replacement Generic Name for fossil Sphenaster Jeffery, 1999 (Echinoidea: Spatangida) nec Wilcoxon, 1970 (Protista: Haptomonada)”. Zootaxa 4139, no. 3 (July 21, 2016): 421–423. Accessed August 28, 2025. https://www.mapress.com/zt/article/view/zootaxa.4139.3.6.