ABSTRACT
Crinoidal limestones are a well known feature of Jurassic carbonate-platform and -ramp settings. However, autochthonous “Lagerstätten” where echinoderms are the dominant group, are only rarely preserved within Mesozoic carbonate sediments. Nevertheless, these fossil assemblages reveal a unique insight into trophic structures and depositional environments of benthic crinoid-communities. The genetic classification of these fossil bonanzas can easily be obtainedThey can be placed into the “Obrution-Lagerstätten”, where living populations have been smothered by stormlayers. Although a few oryctocoenoses are known that have been formed under stagnant conditions. A correlation pattern between Lagerstätten-type and palaeobathymetry can not be recognized. In Mesozoic shallow water carbonate deposits many echinoderm-assemblages display a low faunal diversity but a high population density; almost all of them are epibenthic suspensionfeeder- communities. From the sedimentary record we know that they preferred muddy to bioclastic substrates which have been deposited in the very shallow part of carbonate ramps. The occurence of excellently preserved crinoid assemblages in oolitic sediments is only partly due to selective preservation. The hydrodynamic and ecologic factors which favour the preservation of crinoid-communities (storm-layers etc.) are most likely the same that prevented the settlement by other organisms (Meyer 1988).
