Melanopsis, Unio, Cyrena. A large number of insect genera has been found in the Middle and Lower Purbeck Group. Dinosaurs (Owenodon, Echinodon [known from "Isolated skull elements of at least [three] individuals."]), crocodylians (Goniopholis, Petrosuchus), Cimoliosaurus, the plesiosaurs and the chelonians (Chelone, Pleurosternum) are representative reptiles. The mammals, mostly determined from lower jaws, found in the beds mentioned above include Plagiaulax, Amblotherium, Stylodon, Dorsetodon, Triconodon, Spalacotherium and several others. The isopod crustacean Archaeoniscus brodiei is very common in the Purbeck of the Vale of Wardour. Reptile remains diagnostic to the genus level (Megalosaurus sp (theropod indet), Opisthias) are among the fossils that have been recovered from the formation. Fossil eggs referable to the oogenus Mycomorphoolithus are also known from the Purbeck Group. The silicified stumps and trunks of cycads and coniferous trees, often surrounded by great masses of calcareous concretions (burrs), are very noticeable in the dirt beds of Portland and near Lulworth. Chara is found in the fresh-water cherts of the Middle Purbeck. Use in construction The building stones of the Purbeck Group have already been mentioned; the Purbeck or Paludina "marble", a grey or greenish limestone full of shells, was formerly extensively employed in cathedrals and churches. Stone tiles or slats were once used locally for roofing from the Lower Purbeck of Portland, Swanage and Swindon. Gypsum was formerly worked from the Lower Purbeck at Swanage. See also Geology of East Sussex List of dinosaur-bearing rock formations References Geological groups of the United Kingdom Geologic formations of England Jurassic System of Europe Lower Cretaceous Series of Europe Cretaceous England Jurassic England Tithonian Stage Berriasian Stage Mudstone formations Limestone formations Marl formations Shale formations Ooliferous formations Geology of Dorset