The extinct Solenoporaceae have traditionally been interpreted as a group of red algae ancestral to the Corallinales. The genus from which they take their name, Solenopora, originates in the Ordovician. Unlike the Corallinaceae, this family has large vegetative cells and an undifferentiated thallus.Additionally there are external, non-calcified sporangia. The differences in structure suggest that the holotype is not an alga at all, but rather is a chaetetid sponge. Post-Palaeozoic specimens therefore require re-classification. However, some algal taxa are still classified within the genus.