The Middle Jurassic, called the Dogger in the European system of classification, is the second epoch of the Jurassic period. It lasted from 180-154 million years ago. During this time, marine life (including ammonites and bivalves) flourished, and new types of dinosaurs evolved on land (including cetiosaurs, brachiosaurs, megalosaurs, and hypsilophodonts). In the seas, Ichthyosaurs, although common, are reduced in diversity, while the top marine predators, the pliosaurs, grew to the size of killer whales and larger (Pliosaurus, Liopleurodon). Also in this period Pangea started to separate. The Jurassic period is a major unit of the geologic timescale that extends from about 200 Ma (million years ago) at the end of the Triassic to 146 Ma at the beginning of the Cretaceous. ... Orders and Suborders Order Ammonitida Ammonitina Acanthoceratina Ancyloceratina Phylloceratina Lytoceratina Order Goniatitida Goniatitina Anarcestina Clymeniina Order Ceratitida Ceratitina Prolecanitina Ammonites are an extinct group of marine animals (subclass Ammonoidea) in the phylum Mollusca and class Cephalopoda. ... Orders Subclass Protobranchia Solemyoida Nuculoida Subclass Pteriomorphia - oysters Arcoida Mytiloida Pterioida Subclass Paleoheterodonta - mussels Trigoinoida Unionoida Subclass Heterodonta - clams, zebra mussels Veneroida Myoida Subclass Anomalosdesmata Pholadomyoida Animals of the Class Bivalvia are known as bivalves because they typically have two-part shells, with both parts being more or less symmetrical. ... Orders & Suborders Saurischia Sauropodomorpha Theropoda Ornithischia Dinosaurs were vertebrate animals that dominated the terrestrial ecosystem for over 160 million years, first appearing approximately 230 million years ago. ... Genera Brachiosaurus Cedarosaurus Giraffatitan Lusotitan Brachiosauridae is a family of dinosaurs, whose members are known as Brachiosaurids. ... Megalosaurids were a family of tetanuran theropod dinosaurs, order Saurischia. ... Groups Cymbospondylus Mixosauridae Merriamosauria Shastasauridae/Shastasauria Euichthyosauria Parvipelvia Leptonectidae Thunnosauria Stenopterygidae Ichthyosauridae Ichthyosaurs (Greek for fish lizards) were giant marine reptiles that resemble a dolphin with large teeth (see convergent evolution). ... Families Cryptoclididae Elasmosauridae Plesiosauridae Pliosauridae Plesiosaurs (PLEE-see-oh-SORES) were large, carnivorous aquatic reptiles. ... Liopleurodon was the largest carniverous reptile ever to live on the Earth. ... Map of Pangæa Pangaea (Greek for all lands) is the name Alfred Wegener used to refer to the supercontinent that existed during the Mesozoic era, before the process of plate tectonics separated the component continents. ...