Mesozoic reptiles. Benton: Chapters 6 & 8. G404 Geobiology. Department of Geological Sciences Indiana University

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1 Mesozoic reptiles Benton: Chapters 6 & 8 Gait of Plateosaurus (Mallison, 2010, Palaeontologia Electronica A)

2 Lab Tomorrow: Please bring laptop computers if you have them. Lab assignment will use online DigiMorph data, thus it will be convenient if you have your own computer. If you do not, computers will be available across the hall from the classroom. You will also have the option of completing the assignment on your own over the coming week.

3 Pangea the Late Permian (260 mya) Single continent Massive global extinction Reconstruction by Ron Blakey

4 Tetrapod diversity Permo-Triassic extinction ca. 251 million years ago Nearly 95% of the Earth s species became extinct. 83% Eruption of Siberian traps peaked 251 mya, covering at least 1.6 million square km, an area the size of Europe, with 400 to 3000 m of flood basalt, lasting 600,000 years. Oxygen isotope data suggest rapid global rise in temperature of 6C, which, combined with Pangea s continent configuration, reduced ocean circulation and dissolved oxygen to create anoxic conditions on the floor. Carbon isotope excursions indicate that CO2 increased in atmosphere through production by the Siberian Traps, which raised global temperature enough to melt gas hydrate deposits, which further increased atmospheric CO2 and temperature... runaway greenhouse effect. Tetrapods were hard hit, with the dicyondont Lystrosaurus being one of the few found in fossil record for millions of years after extinction. Forest communities absent until Middle Triassic. Bernard et al, Acta Palaeontologica Polonica, 55: Marine diversity 47% 60% 57% 82% 53% Siberian traps - basalt formations left by surficial lava flow

5 Mesozoic to 65.6 mya Higher sea, smaller continents High atmospheric CO2 Very Hot and Moist Tropics extended nearly to the poles Sea surface temperature at equator as high as 36 C (97 F) Anoxic ocean waters High sea, smaller continents Hot and Moist Large continents Hot and Dry

6 Triassic geography (230 mya) The breakup of Pangea c. Ron Blakey (

7 Triassic geography (230 mya) Extensive deposits in what are today New Mexico and Arizona (Chinle Formation), as well as along east coast (Newark Supergroup) Phytosaur Stanley, Earth Systems Process

8 Jurassic geography (170 mya) Extensive marine and terrestrial deposits in the west, especially (Morrison Formation) Active margin Collision & orogeny Passive margin rifting Stanley, Earth Systems Process

9 Morrison Formation (Jurassic) Camarasaurs lentus from DInosaur National Monument Stanley, Earth Systems Processes

10 Cretaceous geography (75 mya) c. Ron Blakey (

11 Cretaceous geography (70 mya) Hell Creek Formation Terrestrial sediments, Montana Mancos Shale marine sediments, Utah Stanley, Earth Systems Process

12 Phylogeny of reptilia Synapsida Testudines (turtles) Captorhinidae Younginiformes Icthyosauria Lepidosauriformes Plesiosauria Placodontia Archosauria Sauropterygia * lacrimal absent * upper temp fenestra large Lepidosauromorpha * supratemporal absent Amniota Reptilia Diapsida * tabular small or absent * large post-temporal fenestra * single coronoid bone * Upper and lower temporal fenestrae * suborbital fenestra * complex tibio-astragalar joint

13 Testudines - Turtles (aka Chelonia) 328 living species Shell is composed of elongated and flattened ribs, covered with keratin plates Pectoral and pelvic girdles are inside rib cage, teeth lost (in living groups), number of skull bones reduced Oldest turtle: Odontochelys semitestacea, 220 mya (Late Triassic) of China Teeth, plastron (lower shell) and partial carapace (upper shell) Odontochelys semitestacea (from Li et al., 2008, Nature, 456: ) Odontochelys semitestacea (from Li et al., 2008, Nature, 456: ) Archelon in the Vienna Museum of Natural History (Photo by P.D. Polly)

14 Evolution of turtle development Text Kuritani et al., 2001, Evolution and Development, 13: 1-14

15 Icthyosaurs Reptiles convergent on dolphins Originated 245 mya (mid Triassic), became extinct 90 mya (Cretaceous) Live birth Icthyosaurus from the Early Jurassic. (Romer, 1966, Vertebrate Paleontology)

16 Sauropterygia - Plesiosaurs and Placodonts Reptiles convergent on Loch Ness Monster Originated 245 mya (early Triassic), extinction 65 mya (end Cretaceous) Loss of lacrimal bone Placodus skull (placodont) Plesiosaurs Romer, 1966, Vertebrate Paleontology

17 Mosasaurs - marine lepidosaurs Originated early Cretaceous, extinct end Cretaceous Tylosaurus Loss of quadratojugal Tylosaurus Romer, 1966, Vertebrate Paleontology

18 Sphenodon - the tuatara Sister-group to Lepidosauria Lizard that retains full diapsid condition Curtis N, et al PLoS ONE 6(12): e29804.

19 Archosaur phylogeny Euparkeria Phytosauridae Stagonolepidae (incl. aetosaurs) Crocodylomorpha (incl. living crocs) Pterosauria Dinosauria (incl. birds) Crurotarsi * cervical ribs short and stout * mobile joint between astragalus and calcaneum * osteoderm sculpture Avematatarsalia * forelimbs relatively short * pubis elongated * absence of osteoderms * metatarsals 1-4 appressed Archosauria Avesuchia * loss of palatal teeth * reorganization of ankle * Antorbital fenestra * laterally flattened teeth with serrations * laterial mandibular fenestra

20 Crocodiles and relatives Crocodylia - originated 84 mya in Late Cretaceous, still extant Crocodylomorpha - originated in Late Triassic Originally cursorial, living crocodiles and alligators have secondarily sprawling postures Saltoposuchus, crocodylomorph from Upper Triassica Phytosaur Aetosaur (photo from B. Weinert and L. Ferguson-Weinert)

21 Pterosauria Winged archosaurs closely related to dinosaurs Originated 220 mya in Late Triassic, extinct 65 mya at end Cretaceous Ranged from small bird size to the largest flying creature ever, Quetzalcoatalus with wingspan of 11 meters (33 feet) Benton, Vertebrate Paleontology

22 Dinosauria Dinosaur pelvis Ankylosauria Stegosauria Ceratopsia Ornithopoda (incl. hadrosaurs) Sauropodomorpha Theropoda (incl. birds) Ornithischia * cheek teeth with low crowns * muscular cheeks * pubis positioned posteriorly Saurischia * lacrimal exposed on skull roof * additional cervical vertebrae Dinosauria * Quadrate exposed on lateral side * perforatd acetabulum

23 Skull of tyrannosaurids From Holtz and Brett-Surman, in Farlow and Brett-Surman, The Complete Dinosaur (illustrations by Tracy Ford)

24 Reconstruction of Edmontosaurus (Ornithischia, Hadrosauridae) chewing From Rybczynski et al., Palaeontologia Electronica, A

25 Scientific papers for further reading Kuratani, S., S. Kuraku, and H. Nagashima Evolutionary developmental perspective for the origin of turtles: the folding theory for the shell based on the developmental nature of the carapacial ridge. Evolution and Development, 13: Li, C., X-C. Wu, O. Rieppel, L-T. Wang, and L-J. Zhao An ancestral turtle form the Late Triassic of southwestern China. Rybczynski, N., A. Tirabasso, P. Bloskie, R. Cuthbertson, and C. Holliday A three-dimensional animation model of Edmontosaurus (Hadrosauridae) for testing chewing hypotheses. Palaeontologia Electronica, A, 14 pp. Sereno, P. C The evolution of dinosaurs. Science, 284: