Molecular phylogeny of Demospongiae: implications for classification and scenarios of character evolution.

An analysis of the phylogenetic relationships of the 13 orders of Demospongiae, based on 18S and C1, D1 and C2 domains of 28S rRNA (for, respectively, 26 and 32 taxa) has been performed. The class Demospongiae as traditionally defined is not found to be monophyletic. Instead, a clade comprising all demosponges except Homoscleromorpha is well-supported, and we define phylogenetically the name Demospongiae in this more restricted sense to preclude the possibility of drastic alterations of the meaning of Demospongiae in the future, depending on the position of Homoscleromorpha.

Phylogeny and evolution of calcareous sponges: monophyly of calcinea and calcaronea, high level of morphological homoplasy, and the primitive nature of axial symmetry.

Because calcareous sponges are triggering renewed interest with respect to basal metazoan evolution, a phylogenetic framework of their internal relationships is needed to clarify the evolutionary history of key morphological characters. Morphological variation was scored at the suprageneric level within Calcispongia, but little phylogenetic information could be retrieved from morphological characters. For the main subdivision of Calcispongia, the analysis of morphological data weakly supports a classification based upon cytological and embryological characters (Calcinea/Calcaronea) rather than the older classification scheme based upon the aquiferous system (Homocoela/Heterocoela).