Late Valanginian sponge spicules from north-eastern Sardinia (Italy)

Abstract

The knowledge of siliceous sponges of Early Cretaceous age is generally scarce. An interesting assemblage of late Valanginian spicules from NE Sardinia is described. It comprises 21 taxa within two classes, Demospongiae and Hexactinellida. The fauna, which is associated with very abundant radiolarians, seems to be an admixture of morphotypes likely belonging to taxa which have no modern counterparts and spicules identical to those occurring in modern species, such as dischelae of Coelodischela cf. massa, amphitriaenes of Samus cf. anonymus, sterrasters of Geodia sp., and selenasters of Placospongia sp. The fossil record of most of the morphotypes observed in the assemblage dates back to Jurassic or even Triassic. The presence of spicules that belong to shallow-water sponges as well as to forms that inhabit today wide depth ranges, suggests that this Early Cretaceous assemblage lived at depths around 200 m.