Written on 05/17/2022
Mark Milligan

Twenty million years ago, the Swiss Plateau region, or “Mittelland”, was an ocean in which dolphins swam.

Researchers at the University of Zurich’s Palaeontological Institute have discovered two previously unknown species related to modern sperm whales and oceanic dolphins based on a study of fossilised ear bones.

About 20 million years ago the climate became warmer resulting in rising sea levels that flooded the low-lying areas of Europe. Switzerland at the time was part of an island landscape populated by fish, sharks and dolphins, with mussels and sea urchins on the seabed.

Palaeontologists at the University of Zurich have now examined around 300 fossils of whales and dolphins dating from this period. The major natural history and palaeontology collections in Switzerland mostly contain fragments of teeth, vertebrae and ear bones that were found in the Upper Marine Molasse, indicating that strong currents dragged the animal skeletons across the ocean floor and scattered the bones.

Reconstruction of hearing capacity

For research purposes, the most interesting remains are the bones from the inner ear, as they allow individual species to be classified. The problem is that these types of bones are less commonly found. “Nevertheless, we managed to identify two families of dolphins previously unknown in Switzerland,” says palaeontologist Gabriel Aguirre.

Thanks to micro-computed tomography, the researchers were able to reconstruct the softer organs around the hard ear bones to create 3D models of the ears. “This helped us better analyse the dolphins’ hearing ability,” Aguirre explains. According to the study data, the extinct animals are related to the sperm whales and oceanic dolphins living today.

Header Image Credit : Jaime Chirinos