In our last case, that was, I guess, a bit unfair. The fossil visible on the rock is that of a bat, a 30 million year old specimen from the Green River formation, and presently on the Vertebrate Paleontology collection of the American Museum of Natural History (AMNH, in NY).
The Green River is known for its superbly preserved fossils, among which figure bats. The low oxygen conditions, of what seemed to be a shallow lagoon, lake or estuary environment promoted preservation of any organism that fell in its waters, and settled at the muddy bottom. This bat represents one of those such events.
|Archaeopterix specimen (cast) on exhibit at the AMNH. |
Note the tail feather impressions.
Other similar deposits exist at the Messel Pit fossil site, in Germany, where 40 million year old animals are remarcably preserved, along with embrios, stomach content, hair, and sometimes even color. The Solnhofen limestone deposits, also in Germany is another remarkable example. The first Archaeopteryx, the first feathered dinosaur discovered, A. lithographica, was found in the fine-grained limestones of Solnhofen's quarries in 1861. It was called lithographica, because, originally, the fine limestone extrated at those quarries were coveted for the printing industry. The fine-grained feature of Solnhofen's limestone allowed a high degree of detail of the engravings marked upon its printing blocks.
|Lithographic limestone block used for printing. Taken from Pintrest.|