About Pseudonucleus malladai Lambert, 1920 (Echinoidea), from the Campanian of Cantabria (Iberian Peninsula)

This note studies and describes in detail what could be the third known specimen of the rare species of echinid Pesudonucleus malladai Lambert, 1920 from the Campanian of Loredo, in the municipality of Ribamontán al Mar, in Cantabria. The site where it was found is about 55 km in a straight line from where the holotype was found, Roiz (Valdáliga, Cantabria) but the new specimen belongs to the Basque-Cantabrian sedimentary basin and the holotype to the North-Cantabrian basin.
The motivation of the work is to expand the available information about a genus based, until now, only on two poorly preserved specimens, whose validity has been questioned by some authors.
The specimen studied is small, 9.1 mm, and despite not being in excellent preservation it is better than those avai-lable until now.
The study concludes that, based on the material currently available, the validity of the genus Pseudonucleus must be maintained and the echinid studied is left, provisionally, as P. aff. malladai. It presents a significant difference with respect to the holotype in the size and shape of the gonopores, but this could either be because it is a different species or a case of sexual dimorphism: the specimen studied would be a female, of larger, drop-shaped gonopores, while, hypothetically, the holotype would be a male with small, round gonopores.