Fauna of the Upper Jurassic Solnhofen shale. Part 1. Fish

About 155 million years ago, towards the end of the Jurassic period, most of what is now Germany was covered by a warm, shallow sea dotted with islands. Sponges and corals grew on the high ground in that sea, forming reefs that divided parts of the sea into isolated lagoons. According to scientists, the water in them warmed up to 26 degrees, was salty and possibly anoxic (depleted in oxygen) or even toxic at various times. Except for cyanobacteria and small protists like foraminifera, no living beings could survive for long under these conditions. Many organisms that entered the lagoons from the land or drifted and were washed into the lagoons from the ocean, ended up buried in soft carbonate silts. Thus, subsequently, their bodies were not eaten by scavengers or torn apart by the current, but stayed intact until present in layers of light Solnhofen limestone in the region between Nuremberg and Munich.

Initially, these rocks were developed for industrial purpose only. Starting from the mid-18th century, huge dumps of limestone mining (often referred to as shale in the literature of that period and later) attracted the attention of early palaeontologists. Palaeontology as a science was only emerging then.

Such unique places as Solnhofen, the so-called Lagerstätten, may be the only source of information about fossil organisms that would otherwise have left no traces on earth at all. They also make it possible to more accurately reconstruct the ecosystems of the past, because they give an unusually complete picture of the biodiversity of that periods.

By the way, the famous specimen of Archaeopteryx, a «link» between dinosaurs and birds, was found right in the limestone of Solnhofen.

Thanks to the effort of Aleksandr Inostrantsev at the end of the 19th century, the collection of the University’s Geological Cabinet was replenished with a significant collection of both original palaeontological samples of Solnhofen shales and a number of their professional copies made by the F. Krantz company. This collection is still one of the spectacular sections of the museum’s permanent exhibition.

This year, the Palaeontology Museum of St Petersburg University has prepared a series of online exhibitions demonstrating the samples of this collection in more detail. They are sorted in accordance with biological taxonomy.

Kamis