Replica/Casting of Jurassic (150 MA) flying dinosaur, the Pterodactylus kochi, from a fossil found in the Solnhofen limestone formation in Germany.
The Solnhofen limestone formation is a very well-known limestone formation in Bavaria, the Solfhofen has been quarried since the days of the Reformation in the 15th Century. Solnhofen limestone has been used historically for lithographic plates and in sculpture.
The limestone is quite fine-grained, and it formed in stagnant, anoxic environments underwater. Being anoxic and also hypersaline meant that the salt content was incredibly high, even to a level that made the water toxic. This was the Solnhofen in a nutshell.
At this time about 150 million years ago or, the Tithonian Stage of the Late Jurassic, the Tethys Ocean flooded much of Europe and cut it into a massive archipelago.
This area in particular was made of a series of lagoons cut off from the main sea by reefs. It meant that the water in the Solnhofen lagoons was actually left there with hardly any way of flowing back out into the Tethys and so the salt in the water accumulated.
The salinity became far too extreme to support any kind of life. Not even microbial mats could survive here but the silt at the bottom of the lagoons was always fine and grainy.
This made it an excellent preservative for anything small and delicate that happened to crawl, swim or fall into the water.