A new species, Spongia (Heterofibria) catarinensis, is described from Ilha das Aranhas (27º29'077''S, 48º21'380''W), State of Santa Catarina, Brazil. It differs from the other southwestern Atlantic species of this genus by external morphology and architecture. The new species is characterized for presenting massive form, incrusting with lobate projections; primary fibres measuring 60-100 µm; secondary fibres 11,5-69 µm; pseudotertiary fibres 2,3-23 µm and distance between primary fibres 391-920 µm; distance between secondary/pseudotertiary fibres 92-575 µm; secondary/pseudotertiary fibres constituting polygonal meshes 30-700 µm diameter. This species belongs to subgenus Heterofibria Cook & Bergquist, 2001 for displaying a clear dichotomy of its fibres.
Spongia; new species; taxonomy; southwestern Atlantic; Brazilian coast
