Platycrinus niotensis Crinoid | Crawfordsville, Indiana | Mississipian
Carboniferous (Mississippian) 350 Million Years Ago
Specimen: approximately 1.5cm
Plate: approximately 4.75cm x 4cm
Crinoids are marine animals belonging to the phylum Echinodermata and the class Crinoidea. They are an ancient fossil group that first appeared in the seas of the mid Cambrian, about 300 million years before dinosaurs. They flourished in the Palaeozoic and Mesozoic eras and some survive to the present day. Although sometimes different in appearance from their fossil ancestors, living forms provide clues about how fossil crinoids must have lived.
Crawfordsville Indiana is known for its spectacular crinoid faunal assemblage. There are more than 60 species of crinoids among more than 40 genera found in the Crawfordsville area. All major groups of Lower Mississippian crinoids represented: Cladids, Camerates, Disparids, and Flexibles.
Seafloor conditions in the Crawfordsville area were obviously vary favorable to the proliferation of crinoids, an environment that had both shallow water conditions and an influx of silt from a neighboring delta. The crinoids, living in high densities in their tired habitat were periodically buried alive by storm-generated slumping or silt flows. Such tempestites or turbidites must be of sufficient depth to prevent later re-excavation. Collectors are fortunate that the resultant siltstone deposits of Crawfordville are sufficiently soft to allow microabrasive preparation techniques to expose the crinoids in all their past glory, affording the treasures we see today.