Treasure of the month

September 2017

A 175 million year old fish head

The treasure of the month September is a fossilized fish (genus Lepidotes) from the LIB Paleontological Collection. It can be seen in the Museum of Nature - Geology. Fish like Lepidotes (sometimes spelled "Lepidotus") were heavily armored and are also called "ganoid scalers" because of their thick scales.

Our Treasure of the Month is about 175 million years old and dates from the Lower Jurassic. At that time, there was a shallow sea where the Baltic Sea is today, and that's probably where our Lepidotes swam around during its lifetime. However, the piece was found only scarcely 25 km far away from Hamburg near Ahrensburg, and there should not be actually so old deposits at the surface. How is it possible to find rocks over 100 million years old in northern Germany, although most sedimentary deposits here are much younger?

The solution to the riddle is glaciers. During past ice ages, for example during the Vistula Ice Age about 100,000 years ago, glaciers repeatedly extended from Scandinavia into Germany, transporting ancient sediments southward. After the ice melted, the deposits were left behind. LIB owns a particularly large collection of these so-called glacial boulders. The pieces they contain, for example the Lepidotes, are currently being digitally recorded in cooperation with the Archiv für Geschiebekunde.

Photo: UHH, RRZ/MCC, Mentz