Two new species of deep-sea sponges (Porifera, Demospongiae) from submarine canyons of the Sardinian continental margin (western Mediterranean Sea).

Here we describe two new species of deep-sea sponges collected during the exploration of Cold-Water Coral (CWC) banks discovered in the Nora and Coda Cavallo canyons (north-eastern and south coast of Sardinia respectively). Poecillastra tavianii n. sp. differs from the other congeneric species mainly for the dicho- and mesodichotriaenes, never observed in the genus, and the abundance and variety of spirasters. Hymedesmia (Hymedesmia) quadridentata n. sp. is characterized by the presence of two types of chelae. In particular, the unguiferate chelae (round shaft and four teeth at both extremities) represent a peculiar character of the species. Our contribution increases the number of sponge fauna associated to the best known Central Mediterranean CWC habitats to 98 improving the still scant knowledge on the biodiversity of the Mediterranean CWC habitats.