aquatic Crinoidea Echinodermata fossil invertebrate marine museum organism Palaeontological site rock science Sea lily siltstone bones carnivore carnivorous cast display extinct feet head Inostrancevia jaw reptile skeleton skull teeth arthropod cambrian period evolution geology stone time trilobite dinosaur fang jaws predator Tarbosaurus tooth ancient animal background catastrophe disaster fish fishes flat flattened impression Mineral mineralised nature old Remains shoal texture cambrian eolith neolith paleolith period petrifaction reconstruction relic specimen St trace