Spongillida

Spongillida is an order of sponges in the subclass Heteroscleromorpha, originally described as the suborder Spongillina. Members of this order are exclusively freshwater animals, and all freshwater sponges are currently considered part of this order, though the monophyly of this group has not yet been confirmed; it is currently unknown whether all freshwater sponges belong within a single natural group.

The main method of identifying and classifying sponges rely on morphology and genetics; in freshwater sponges, morphological methods analyze skeletal architecture, forms of the spicules, and traits of the gemmules. Some species, especially those endemic to ancient lakes (such as rift lakes) have lost the ability to create gemmules, necessitating other identification methods. Genetic analysis is often relied upon due to lack of clarity surrounding diagnostic aspects of morphology. Other than Arinosaster, all species of this order are currently placed within one of the seven families.