A new calcitic Sphinctozoan sponge belonging to the demospongiae from the Cassian formation (Lower Carnian; Dolomites, northern Italy) and its phylogenetic relationship

Abstract

A new species of a coralline sponge, Cassianothalamia zardinii n. gen. n.sp., from the Lower Carnian Cassian Beds (northern Italy) is described. The new species possesses a secondary thalamid basal skeleton with a spongocoel and the internal structure is constructed of horizontal elements (trabecula) and vesiculae. The microstructure of the basal skeleton is composed of an irregular high Mg-calcite. From the spicular skeleton aster-microscleres can be preserved. In rare cases, monaxonid megascleres can also be found. Therefore the new sponge is probably a representative of the demospongid order Hadromerida.

Une nouvelle espece d'eponge coralline, Cassianothalamia zardiini n.gen. n.sp., a ete trouvee dans les couches du Carnien inferieur de Saint-Cassian. La nouvelle espece possede un squelette basal thalami de secondaire muni d'une cavite pseudogastrique et sa structure interne est constituee d'eIements horizontaux (trabecules) et de vesicules. La microstructure de la partie basale du squelette est composee d'une calcite irreguliere a forte teneur en Mg. Les microscleres asteroYdes du squelette spiculaire peuvent avoir ete conserves. On peut aussi trouver tres rarement des megascleres monaxonides. Par consequent, cette nouvelle eponge est probablement un representant de l'ordre Hadromerida des Demosponges.