It is Pilumnus spinifer. In the foto I see strong sub-distal spine on dorsal margin of carpus on 3^ and 4 pereiopods. This carachter is present also in P. villosissimum, but P. spinifer has front acutely denticulated. and exagonal carapace. Carapace is more squarish in P. villosissimum. In addition check the setae: In P. spinifer setae are stiff, in P. villosissimum setae are more dense, very thiny and soft.
Dear Roberto, I have one PhD student finishing her project on phylogeny of Pilumnus from America. This species P. spinifer is useful for our aims, just to comparative analysis. So, if you are interested, we can run a DNA analysis to you in order to confirm the identification. For this, it would be nice to have one individual for tissue extraction and run the analysis. If you are interested, let me know. Best wishes, Fernando