TAPHONOMY OF ARTHROPOD CUTICLES FROM PLIOCENE LAKE-SEDIMENTS, WILLERSHAUSEN, GERMANY

The Pliocene lake sediments at Willershausen, Germany, have yielded a diversity of remarkably preserved fossils, including crayfish and inse cts. The internal structure of the cuticle of the crayfish Astacus and of insects is preserved but shows evidence of some degradation. Chiti n. and amino acids survive, although the quantity that remains is vari able. The proportion of chitin in the cuticle of the modern crayfish P acifastacus (12.2%) is higher than that in Astacus from shallow depths in the Willershausen paleolake (5%), indicating that the fossils have undergone degradation. Analyses of the cuticles of these crayfish fol lowing demineralization show that some chemical components, which were presumably bound to the carbonate, are lost. The proportion of chitin (40%) in the cuticle of a weevil from the deeper part of the stratifi ed paleolake (below the chemocline) is comparable to that in the cutic le of modern beetles. A much lower proportion of chitin (2-5%) survive s in the cuticle of insects from the shallower oxygenated part of the paleolake, indicating that intensive degradation has occurred. Thus de positional setting, and biomineralization, influence the preservation of the organic constituents of fossil arthropod cuticles.