Over 1,000 mammal discovery sites have been found in the deposits of the Swiss Molasse basin that were formed 5 million to 34 million years ago.

The Molasse basin is a large area to the north of the Alps that is home to significant sedimentary deposits. Hans Georg Stehlin was one of the first palaeontologists to systematically search for mammals in the Swiss Molasse area. In 1914, he published a summary of the sites and their individual fauna.

From his early youth, Johannes Hürzeler collected in the Molasse basin and put together extensive collections of fossilised mammal remains. Over many years of work, he also drew up a register of the mammal discovery sites from the Swiss Tertiary period, keeping a record of all of the available data and documents.

From 1978 to 1999, the then Osteology Department at the Natural History Museum Basel, led by Burkart Engesser, primarily collected small mammals as part of various Swiss National Science Foundation projects in the Swiss Molasse region. During this period, some 50 tonnes of sediments were washed and around 30,000 small mammal teeth were recovered.

This collection allowed our researchers to develop a precise chronological scale of Switzerland's last 45 million years.