First record of Galeaster bertrandi Seunes, 1889 (Echinoidea) in Nafarroa

An adult specimen of the rare echinoid Galeaster bertrandi Seunes, 1889 which had not yet been recorded in Nafarroa, is described in detail, despite the existence of some in-depth work on the Maastrictian-Paleocene period in the Basque-Cantabrian basin to analyze the effects of the extinction at the end of the Cretaceous. The species is of great interest because it crossed the K/T border; because it is an echinoid belonging to the deep-water fauna, not sufficiently studied; because some authors consider that genus Galeaster could be the origin of the current family Pourtalesiidae A. Agassiz, 1881 and because there are characteristics of the species (such as the apical system) that are still poorly known. Only one specimen was available, in which the groove of ambulacrum III and the peristome have been cleaned. In terms of systematics, Kroh & Smith, (2010) and Kroh & Mooi (2022) are followed. For the inclusion of the specimen within the species G. bertrandi, it has been compared with the holotype. With this first record in Nafarroa (Danian) it is confirmed in the Basque-Cantabrian basin itself, that the species crossed the K/T border, because the specimen from Cabo Mayor at Santander is of Maastrichtian age. It has been confirmed the existence of an adult specimen that does not have genital plates 2 and 3 fused and whose posterior gonopores open inside on the posterior genital plates and not on oculars II and IV as postulated by some authors. The generic diagnosis has been partially amended. We describe for the first time the particularities of interambulacra 1 and 4 on the oral surface, in which the plate bordering the peristome and the next, which is also single, are disjunct (separated). The variability in the architecture of the plates, both in the species and in the genus and the fact of being related to the current family Pourtalesiidae on which some aspect of the Extraaxial-Axial theory (EAT) has been relying makes its study interesting and field work necessary in search of more specimens until reaching a significant sample.