Whales died out in the Mediterranean because of extreme salt levels. | Pixabay

Researchers at the University of the Balearic Islands biology department have presented preliminary findings regarding the discovery of a whale skull fossil calculated to be 5.7 million years old. It was found in a block of Santanyi stone weighing some 750 kilos at a quarry near S'Horta in Felanitx.

The Santanyi stone corresponds to a stratigraphic layer related to the so-called Messinian Salinity Crisis when there was a cycle of partial or almost complete desiccation in the Mediterranean. This occurred between 5.33 and 5.96 million years ago. The discovery in Felanitx is the first and only one of a whale fossil to have been made which matches that geological epoch.

Large cetaceans, i.e. whales, underwent a process of extinction because of the extreme levels of salt. They were reestablished when marine conditions returned to normal during the following epoch - the Pliocene between 2.58 million and 5.33 million years ago.

Study of the fossil suggests that the whale was up to eight metres long and weighed between seven and eight tonnes. It bears similarities with the current rorqual family of whales, perhaps a minke.