Two new species of ancient cetaceans related to modern dolphins and sperm whales have been identified from the 20-million-year-old fossilized ear bones found in Switzerland.
“About 20 million years ago, as the climate became warmer and warmer, sea levels rose and flooded the low-lying areas of Europe,” said University of Zurich paleontologist Gabriel Aguirre-Fernández and his colleagues.
“Switzerland at that time was part of an island landscape populated by fish, sharks and dolphins, with mussels and sea urchins on the seabed.”
In the research, Dr. Aguirre-Fernández’s team examined cetacean assemblage from the so-called 20-million-year-old Upper Marine Molasse, a 100-m-thick sequence of fossil-bearing sediments in Switzerland.
The researchers focused on the identification and interpretation of periotics (bone that contains the inner ear).
“Periotics are rare, but they provide the richest taxonomic information in the sample and hint to environmental associations,” they said.
They used micro-computed tomography to analyze seven cetacean periotics from the Upper Marine Molasse.
They found that the specimens belonged to three families: Kentriodontidae, Squalodelphinidae and Physeteridae.
“We managed to identify two families of dolphins previously unknown in Switzerland,” Dr. Aguirre-Fernández said.
“Thanks to micro-computed tomography, we were able to reconstruct the softer organs around the hard ear bones to create 3D models of the ears.”
“This helped us better analyze the dolphins’ hearing ability.”
The team’s paper appears online in the journal PeerJ.
G. Aguirre-Fernández et al. 2022. First records of extinct kentriodontid and squalodelphinid dolphins from the Upper Marine Molasse (Burdigalian age) of Switzerland and a reappraisal of the Swiss cetacean fauna. PeerJ 10: e13251; doi: 10.7717/peerj.13251
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