Presentation on theme: "6. From Meso- to Cenozoic Triassic 250-205 Pangaea Jurassic 205-140 Laurasia and Gondwana Cretaceous 140-65 Formation of present day continents Hot and."— Presentation transcript:
6. From Meso- to Cenozoic Triassic 250-205 Pangaea Jurassic 205-140 Laurasia and Gondwana Cretaceous 140-65 Formation of present day continents Hot and dry Polar regions moist and temperate Warm and dry No ice caps at poles Very warm no ice caps at poles. Ocean temperatures about 15-20º higher than today Pangaea
Cretaceous 140-65 Formation of present days continents Very warm no ice caps at poles. Ocean temperatures about 15-20º higher than today From Müller et al. 2008)
DevonianTriassianPermianCarboniferousCretaceousJurassicTertiary to recent Palaeodictyoptera Odonata Ephemeroptera Dictyoptera Plecoptera Zoraptera Embioptera Isoptera Grylloblatodea Dermaptera Phasmida Orthoptera Mallophaga Psocoptera Thysanoptera Heteroptera Hymenoptera Neuroptera Coleoptera Mecoptera Siphonaptera Diptera Lepidoptera Trichoptera Genetic diversific ation In the Triassic period all extant taxa already existed The rise of insects Adaptive radiation
The rise of holometabolous insects Jurassic Cretaceous
Cretaceous 140-65 Photos from: http://www.fossilmuseum.net/Fossil_Galleries/Insect_Galleries_by_Order/ Paleogene 65-23 The earliest ants An early bee A swarm of midgesThe earliest moth An early lacewingAn early weevilA weevil in amber
The Cretaceous –Tertiary impact K-T boundary The K-T boundary. The arrow indicates a layer of Iridium rich ash. Iridium is rare on the surface of the earth but much more common in Chondrite meteors Luis Alvarez 1911- Walter Alvarez 1940- The Chicxulub Impact structure buried beneath the Yucatan Peninsula has 150 - 300 km in diameter Age dates of melt rock in the structure have at date of 65 Ma.
The K-T layer is divided into two parts, the Magic Layer (3 mm thick) and the Ejecta Layer (2 cm thick). They contain Siderophiles contain the rare Earth Elements Os, Au, Pt, Ni, Co, Pd, and Ir. Iridium (Ir) has been found in the K-T layer around the world (New Zealand, Denmark, and Italy). The layer is about 100,000-years-thick. Tektites are abundant in the K-T layer.They are quartz grains which are vaporized under intense heat and pressure, and cool into glass beads with no crystalline structure. Tektites were probably formed during a meteorite or comet collision. Shocked quartz - When quartz is put under extremely high pressure, it can cleave in parallel planes. Shocked quartz is found at nuclear bomb sites and known meteorite impact areas. Shocked quartz is abundant in the K-T layer. Stishovite (Silicon Dioxide) - a form of quartz created under conditions of high heat and pressure. It is used as an indicator of meteor impact. It has been found in abnormally high abundance in the K-T layer. Glass beads - Kenneth Miller has discovered a two-inch layer of glass beads in the K- T layer near the Bass River in New Jersey, USA, supporting Alvarez' theory.
Extinctions at the K-T boundary were not evenly distributed across taxa 15% of all marine families went extinct, 50 % at generic level, maybe 80-90 % of all species. Affected were mainly plankton, marine predators, and shallow water communities. 25 % of terrestrial families and 56 % at generic level went extinct. Nothing bigger than 25 kg survived (predators and herbivores). Unaffected were higher plants (10% extinction), mammals (rise of 20%), and birds. However, dinosaur diversity declined even before the impact. Probably the impact wiped out the last survivors.
Cretaceous and Paleogene saw an enormous diversification of Angiospermes Holometabolic insects (Coleoptera, Hymenoptera, Lepidoptera, Diptera) Mammals Birds Gastropods a decline in diversity of Gymnospermes Brachiopods the extinction of Ammonites Belemnites Dinosaurs Global species richness of dinosaurs Data from Sullivan (2006)
Today’s reading The Mesozoic era: http://www.palaeos.com/Mesozoic/Mesozoic.htmhttp://www.palaeos.com/Mesozoic/Mesozoic.htm http://www.palaeos.com/Mesozoic/Mesozoic2.html The Cenozoic era: http://www.palaeos.com/Cenozoic/Neogene.htmlhttp://www.palaeos.com/Cenozoic/Neogene.html http://www.palaeos.com/Cenozoic/Paleogene.html