A Jurassic lagoon floor
During the Late Jurassic, around 150 million years ago, this part of Bavaria was a subtropical archipelago in the warm Tethys Sea. The Solnhofen Plattenkalk, or Solnhofen Limestone, formed in the stagnant basins and lagoons between coral and sponge reefs. The water in these lagoons was largely cut off from the open sea, leading to high salinity. The bottom layers of water were anoxic, meaning they lacked oxygen. This combination of salty, oxygen-poor water and fine-grained calcium carbonate mud created a toxic environment where scavengers could not survive. Any organism that fell into the lagoon and sank to the bottom was rapidly buried and left undisturbed, leading to a state of exceptional preservation known as a Lagerstätte. Even the impressions of soft tissues like jellyfish bells, dragonfly wings, and the feathers of Archaeopteryx were preserved in fine detail.
A library of ancient life
The fossils found here represent a cross-section of terrestrial, marine, and aerial ecosystems. Over 750 species have been identified from the limestone beds. The quarries have yielded famous pterosaurs like Pterodactylus and Rhamphorhynchus, with some specimens even showing the delicate membranes of their wings. Marine life is abundant, including ammonites, crustaceans like the shrimp Acanthochirana, and a wide variety of bony fish. Terrestrial animals are also present, including the small predatory dinosaur Compsognathus. One specimen of Compsognathus contained the remains of a lizard called Bavarisaurus in its stomach cavity. The most well-known fossil is Archaeopteryx, a feathered dinosaur whose first definitive specimen was found in 1861. All known skeletons of this important transitional fossil come from the Solnhofen quarries. The name given to the first species, Archaeopteryx lithographica, directly references the stone in which it was found.
The reason for these fossil discoveries is tied directly to the stone's unique physical properties. The limestone is flat, fine-grained, and smooth, which made it the perfect material for lithography, a printing process invented by Alois Senefelder in 1798. The intensive quarrying for these lithographic stones throughout the 19th century led to the unearthing of thousands of scientifically valuable fossils that would have otherwise remained hidden. Before its use in printing, the stone was primarily quarried for roofing tiles and flooring.