Solnhofen Limestone

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Solnhofen - Barthel et al. 1990

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"This fine-textured limestone was quarried near Solnhofen and Eichstatt in the Altmuhl Valley, Bavaria, for many generations and sent to all parts of the world for use in the preparation of lithographic prints which played such an important role in the first publication of books. Immediately the presence of fossils and impressions of others were recognized. For here were not only the hard parts of extinct animals, but also the outlines of their soft parts so rarely preserved as fossils. Over 450 kinds of animals have been taken from these quarries.

"In the late Jurassic these fine sediments were laid down in a lagoon evidently on an island in the Tethys Sea. The lagoon must have been separated from the sea by a reef formed of corals and sponges much like those in certain parts of the Pacific Ocean today. It was near shore because it appears at times to have dried up and have been flooded again with sea water. This would account for the assemblage of land-living vertebrates and marine life that became entombed in the sticky, limy ooze formed primarily from fine, coralline debris that had settled on the floor of the lagoon. Animals were buried so quickly that their skeletons were not disarticulated and in most instances the soft parts did not deteriorate before their outline was preserved.

"Insects were abundant and, in some specimens, well preserved, giving a rather clear picture of their numbers and variety. There were moths and flies not known from older rocks. Soft-bodied animals like jellyfish, so rarely preserved as fossils, also were found. No fresh-water invertebrates were present but, numerous marine crustaceans, belemnites, and ammonites were discovered, together with an abundance of marine fishes. An unexpected find was a small dinosaur, no larger than a rooster, and its young, which somehow found their way into the lagoonal ooze. Pterosaurs also were trapped in the sticky substance, perhaps as they attempted to swoop down on some struggling creature.

"Twenty-nine kinds of pterosaurs, ranging from the size of a sparrow to others 4 feet in length, have been found. These interesting fossils showed how the delicate gliding membranes were supported by the greatly elongated fourth digit. One pterosaur had a long tail with a steering rudder at its end, and another was almost without a tail. But the most remarkable of all these creatures at Solnhofen was the oldest feathered animal known. This was the first bird, Archaeopteryx, about the size of a crow. Two most welcome specimens represented by their skeletons and an isolated feather would surely have been called reptiles if clear-cut impressions of their feathers had not been preserved. Though there were birdlike features in the skull and pelvis, the skeletons were more like those in reptiles. The bones were solid, not hollow and pneumatic (with air sacks), as in most modern birds, and the jaws were lined with sharp lizardlike teeth. Even a cast of the brain was more like that in reptiles than in birds. These unique animals and their unusual preservation in the old Solnhofen lagoon have made valuable contributiqns to our knowledge of little-known extinct animals not found elsewhere in the world. The discovery of Archaeopteryx settled the long-debated question on the origin and relationships of birds, for it is now clear that they arose from a primitive group of diapsid reptiles, a group that would also include the ancestry of the dinosaurs and phytosaurs" (Stirton 1959, pp. 268-269).

"In the Upper Jurassic lithographic limestones of Solnhofen, only nine specimens of only two kinds of dinosaurs have been found: Archaeopteryx and Compsognathus. Both have been considered as the smallest known dinosaurs and are of particular interest concerning the understanding of dinosaur and bird evolution. The exceptional preservation in the lithographic limestones led to the recovery of the first known Mesozoic bird feather. Strtigraphically, the Solnhofen Formation has been assigned to the lower part of the lower Tithonian. Its occurence is restricted to the southern Franconian Alb of Bavaria. The evenly layered limestones are intercalated with fine-layered marls that originated in depressions between algal-sponge reefs in lagoon-like environments positioned on the northern rim of the Tethys. The carbonate accumulations and fossil assemblage indicate warm, semi-arid climatic conditions (Viohl, 1985). Compsognathus and Archaeopteryx lived on islands along the shoreline of a slowly emerging central German swell to the north. Within the fossil record of the formation there is no evidence of trees or cliffs, but bushland vegetation alternated with open plains. In addition to Compsognathus and Archaeopteryx, pterosaurs and lizards have been recovered from the Solnhofen limestones. The rareness of dinosaurs in this intensively sampled deposit is surprising" (Haubold 1997, pp. 676-677).

References

Barthel, W.; Morris, S.C.; Swinburne, N.C. 1990: Solnhofen, 2nd ed. Cambridge University Press.

Haubold, Hartmut 1997: Solnhofen Formation. In Currie, Philip J.; Padian, Kevin (eds.) 1997: Encyclopedia of Dinosaurs. Academic Press, pp. 676-677.

Stirton, R.A. 1959: Time, Life and Man. Wiley, 558 pp.

Viohl, G. 1985: Geology of the Solnhofen Lithographic Limestone and the Habitat of Archeopteryx. In Hecht, M.K.; Ostrom, J.H.; Viohl, G.; Wellnhofer, P. (eds.) 1985: The Beginnings of Birds. Eichstatt. Freude des Jura-Museums Eichstätt, Willibaldsburg, pp. 31-44.

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