Amphoriscus is a widespread genus with 17 species. A new species was found in SE Brazil and it represents the second species of this genus in Brazilian waters. Amphoriscus pedunculatus sp. nov. has a special structure, a peduncle, to attach to the substrate. Special attachment structures are not very common in the class Calcarea but this is the third species of the genus with a peduncle. Besides peduncle, another attachment structure found in some species of Amphoriscus is the root-tuft, an attachment structure composed of diactines and anchor-like triactines or tetractines. The evolution of these attachment structures in Amphoriscus is not known but they have also been found out of this genus, suggesting that these structures appeared several times during the evolution of Calcarea or that species currently classified in different genera are in fact congeneric.
Keywords: Porifera, Calcaronea, biodiversity, peduncle, root-tuft, taxonomy.