Nudibranchs belong to phylum Mollusca, class Gastropoda ... Nudibranchs get their name from the feathery gills exposed on their backs. The word nudibranch actually means "naked gills." ...

Both Punk and Emo are described as worm-like mollusks with long spines and smooth undersides that suggest they inhabited the seafloor. Punk had gills and a broad foot with ridges on the bottom ...