What features besides outward appearance can biologist use to classify sponges and eliminate some of this confusion?

Biologists can classify sponges based on several key features beyond their outward appearance, including their skeletal structure, which can be composed of spicules made of silica or calcium carbonate. They also examine the arrangement and types of canal systems, which can be classified as asconoid, syconoid, or leukonoid. Additionally, the presence of specific cell types, such as choanocytes and archaeocytes, and genetic analyses can provide insights into their classification and evolutionary relationships. These features help clarify the diversity among sponge species and reduce confusion arising from their similar external forms.