The skulls, discovered in the 19th century as part of work in a gold mine that operated on the fossil cliff of Adiça beach, in the municipality of Almada, are part of the collection of the National Museum of Natural History and Science, in Lisbon, where they can be seen from next weekend until mid-April.

In the study, published in the open access scientific journal PLOS ONE, Rui Castanhinha and the rest of the team describe, based on new information obtained from phylogenetic analyses and advanced computational methodologies, that the two whale fossils belong to the new genus 'Adicetus', renaming the specimens as 'Adicetus latus' and 'Adicetus vandelli'.

The name 'Adicetus' results from the combination of the terms 'Adiça', which refers to the name of the place where the skulls were found, and 'Cetus', which means whale or sea monster.

Rui Castanhinha, researcher in the field of evolutionary biology at the Center for Environmental and Sea Studies at the University of Aveiro and paleontologist at the Lourinhã Museum, justified to Lusa the naming of a new genus for these two fossil whales with the fact that they share characteristics " very closely" which differentiates them from the groups designated in 1871 by the Belgian biologist Van Beneden ('Metopocetus') and in 1941 by the North American naturalist Remington Kellogg ('Aulocetus').

The terms 'latus' and 'vandelli' were maintained by Rui Castanhinha's team, with the last of the names referring to Alexandre António Vandelli, son of the naturalist Domingos Vandelli who collected the skulls.

According to Rui Castanhinha, the skulls belong to specimens of whales that lived on the Portuguese coast 11 million years ago, when the fossil cliff at Adiça beach "was at the bottom of the sea".

"They were not very large whales, measuring four to six metres", he noted, adding that the work carried out, which stemmed from the "need for a detailed description" of the fossils, demonstrates that the study of the collections of natural history museums "never ends".