|Basic info||Taxonomic history||Classification||Relationships|
|Morphology||Ecology and taphonomy||Age range and collections|
Echinoidea - Nucleolitidae
It was reranked as Nucleolites (Pygorhynchus) by Forbes (1846); it was reranked as Cassidulus (Pygorhynchus) by Clark and Twitchell (1915).
It was assigned to Nucleolites by Forbes (1846); to Cassidulus by Clark and Twitchell (1915); to Nucleolitidae by Kier (1966); and to Cassiduloida by Sepkoski (2002).