Cycleryon propinquus (Schlotheim, 1822) - fossil crustacean from the Jurassic of Germany. (ventral view) (CM 33074, Carnegie Museum of Natural History, Pittsburgh, Pennsylvania, USA)

The crustaceans are a large group of arthropods that inhabit marine, marginal marine, freshwater, and terrestrial habitats. The crustaceans include crabs, lobsters, shrimp, crayfish, barnacles, ostracods, and other organisms. The oldest fossil crustaceans are in the Cambrian. The group experienced a significant radiation in the oceans during the Mesozoic Marine Revolution.

The fossil crustacean shown here is from the famous Solnhofen Limestone, a deposit that includes soft-part preservation. The number one most famous fossil on Earth came from Solnhofen - Archaeopteryx, which is literally half-reptile, half-bird (creationists hate that fossil). The Solnhofen is a lagoon deposit that has marine, nonmarine, and marginal marine organisms, including animals and plants.

From museum signage:

Fossils from the quarries of Solnhofen in southern Germany reveal the rich variety of life that thrived in and around Late Jurassic seas.

The ancient environmental conditions at Solnhofen resulted in the remarkable preservation of fossils representing hundreds of Late Jurassic plant, invertebrate, fish, reptile, and bird species. A series of shallow, tropical lagoons extended across southern Europe during this time. Reefs and rock outcrops sheltered these waters from the action of waves and tides. When organisms died in these quiet lagoons, they often sank to the bottom to be buried by fine-grained sediments. The water at the bottom of many Solnhofen lagoons contained little or no oxygen. These conditions not only spared many carcasses from damage or decomposition by bacteria and other scavengers, but also helped to preserved delicate soft-tissue features such as skin, scales, and feathers in exquisite detail.

Classification: Animalia, Arthropoda, Crustacea, Malacostraca, Decapoda, Eryonidae

Stratigraphy: Solnhofen Limestone, Upper Jurassic