what are starfish classified as
Jupiterimages/Photos.com/Getty Images. Starfish belong to the phylum Echinodermata. Mollusks are a separate phylum of animals. Although both phyla are made up of invertebrates, differences in their anatomy are why starfish are classified as echinoderms and not mollusks.Echinoderms have spiny skin and many physical attributes that are unique in the animal kingdom.ollusks are a separate phylum of animals. Although both phyla are made up of invertebrates, differences in their anatomy are why starfish are classified as echinoderms and not mollusks.