Abstract Hypercalcified calcareous sponges represent a relic group with a complex evolutionary background and unresolved taxonomy. This study revisits the systematics of sponges with reinforced skeletons using morphological and molecular tools, with a focus on Calcinea. Our analyses recovered Murrayona and Lelapiella as monophyletic genera but distantly related, confirming the abandonment of the former order ‘Murrayonida’. A comparative analysis identified five distinct types of reinforced skeletons in Calcarea. Three of these are actual hypercalcified skeletons with different structure patterns, while the others suggest convergent evolution across Calcinea and Calcaronea, where scales appear to be the only real type of reinforcement. The true species richness of calcareous sponges with reinforced skeletons is likely underestimated because certain widespread species (e.g. Murrayona phanolepis and Paramurrayona corticata) may represent several cryptic species. Furthermore, despite a suggested role in past reef ecosystems, limited fossil records hinder definitive confirmation of a hypothetical historical shift from exposed reef builders to a current occurrence in cryptic habitats. The consistent cryptic habitat preference through time suggests Calcarea may have always favoured protected environments, although comprehensive fossil data remain scarce. Finally, this study also describes three new species to science: Murrayona laevis sp. nov., Murrayona spinifera sp. nov., and Lelapiella annularis sp. nov.
Lopes et al. (Thu,) studied this question.