Dawn of the Dinosaurs: Drivers of Early Dinosaur Diversification and Biogeography in the Early Mesozoic
Nathan Smith
The Dinosaur Institute Natural History Museum of Los Angeles County
Educational Outreach – California NGSS for High School Students HS.LS2.A: Interdependent Relationships in Ecosystems HS.LS2.C: Ecosystem Dynamics, Functioning, and Resilience HS.LS4.A: Evidence of Common Ancestry and Diversity HS.LS4.C: Natural Selection HS.LS4.C: Adaptation ESS1.C: The History of Planet Earth ESS2.B: Plate Tectonics and Large-Scale System Interactions ESS2.E: Biogeology ESS3.D: Global Climate Change PS4.C: Information Technologies and Instrumentation
Educational Outreach
Evolutionary Trees Amnion - - + ? + +
Chorion Most Recent Amnion Common AncestorEmbryo Parental Care of Nest - - - + +? +
Most Recent Common Ancestor The Assembly of Complex Anatomy
† F † Fossil E † species D “Avian” † C † Traits B A The Assembly of Complex Anatomy
“Avian” Traits
† Sternal keel † Fossil Triosseal canal † Asymmetric feathers species † Semilunate carpal † Strap-like scapula Furcula The Assembly of Complex Anatomy
“Avian” Traits
† Sternal keel † Fossil Triosseal canal † Asymmetric feathers species † Semilunate carpal † Strap-like scapula Furcula Early Dinosaur Relationships & Origin of the Avian Body Plan
Climatic & Biotic Controls on Early Dinosaur Ecosystems & Biogeography
Archosauria Archosauria
Dinosauria
Dinosaur ‘precursors’ 201 mya
235 mya
245 mya The Late Triassic World Pangea: Major rifting will begin in Early Jurassic
Relative Newcomers: Turtles, Mammals, Lepidosaurs, Pterosaurs, Dinosaurs
Mass Extinction: 5th largest of all time; ~80% of species; 40% of genera; all pseudosuchians except crocodylomorphs
The Late Triassic Hayden Quarry
Hayden Quarry Geology
• Mixed mudstone, 2 m 2 m sandstone, conglomerate • Abraded bone fragments to articulated skeletons • Abundant charcoal 40X 1 m
Interpreta on:
1. High-energy river channel
2. Alterna ng flooding and exposure
Hayden Quarry Vertebrate Fossils
Coelacanth Fish Amphibians Vancleavea
Crocodylomorphs Tanystropheidae
Aetosaurs Drepanosauridae
Postosuchus-like animal Phytosaurs “Rauisuchian” Hayden Quarry Vertebrate Fossils
Coelacanth Fish Amphibians Vancleavea
Aetosaurs Drepanosauridae Tanystropheidae Crocodylomorphs
Postosuchus-like animal Phytosaurs “Rauisuchian” The Late Triassic was weird…
Coelacanth Fish Amphibians Vancleavea
Aetosaurs Drepanosauridae Tanystropheidae Crocodylomorphs
Postosuchus-like animal Phytosaurs “Rauisuchian” Scale bars = 10mm
Theropod Dinosaurs
Irmis, Nesbitt, Padian, Smith et al. 2007, Science Silesauridae† Scale bars = 10mm
Irmis, Nesbitt, Padian, Smith et al. 2007, Science Dromomeron romeri 201 mya
235 mya
245 mya Archosaur Hindlimb Musculature
Nesbitt, Irmis, Parker, Smith et al. 2009, JVP (Muscle homologies/topologies from Carrano & Hutchinson, 2002) Archosaur Hindlimb Musculature
Nesbitt, Irmis, Parker, Smith et al. 2009, JVP (Muscle homologies/topologies from Carrano & Hutchinson, 2002) Archosaur Hindlimb Musculature
Dromomeron gregorii growth series Nesbitt, Irmis, Parker, Smith et al. 2009, JVP (Muscle homologies/topologies from Carrano & Hutchinson, 2002)
Tawa hallae
Nesbitt, Smith et al. 2009, Science Scale bar = 10mm Nesbitt, Smith et al. 2009, Science Scale bar = 10mm Nesbitt, Smith et al. 2009, Science Nesbitt, Smith et al. 2009, Science Early Dinosaur Relationships & Origin of the Avian Body Plan
Climatic & Biotic Controls on Early Dinosaur Ecosystems & Biogeography
middle Norian–Rhaetian ~225–202 Ma
Coloradisaurus (©Mohamad Haghani 2012)
late Carnian–early Norian ~232–223 Ma
Whiteside et al. 2015. PNAS
i p w i
cuticle w
stomata with guard cells p p pt pt p
pt w Rapid Fluctuations in Climate & Plant Communities
Whiteside et al. 2015. PNAS Rapid Fluctuations in Climate & Plant Communities
Whiteside et al. 2015. PNAS Early Dinosaur Climatic & Biotic Controls Relationships & on Early Dinosaur Origin of the Ecosystems & Avian Body Plan Biogeography
Key Takeaways
• Dinosaurs did not rapidly rise to dominance in Late Triassic ecosystems
• The “Rise of Dinosaurs” was a diachronous event, which may be partly explained by climate and plant community differences
• Many “Key” aspects of the avian body plan were already present in early dinosaurs and their relatives
• Dinosaurs are an effective and accessible system for teaching the public about evolution and biotic response to climate change
Early Dinosaur Climatic & Biotic Controls Relationships & on Early Dinosaur Origin of the Ecosystems & Avian Body Plan Biogeography
Obligatory NHM plug… Colleagues: Ian Glasspool, Randall Irmis, Sophi Lindström, Sterling Nesbitt, Jennifer Olori, Kevin Padian, Bill Parker, Adam Pritchard, Alan Turner, Sarah Werning, Jessica Whiteside
Funding: National Science Foundation (EAR 1349554, ANT 1246379, 1341475, DEB 1331980); National Geographic Society CRE #8014-06, CRE #9849-16
Collections: American Museum of Natural History; Field Museum of Natural History; Ghost Ranch Ruth Hall Museum of Paleontology; Museo Argentino de Ciencias Naturales; Museo Paleontológico Egidio Feruglio; Museo Patagonica de Ciencias Naturales, Museo Provincial Carlos Ameghino; Petrified Forest National Park; Fundacíon Miguel Lillo; Museo de Ciencias Naturales, San Juan; Texas Memorial Museum; University of California Museum of Paleontology; Universidad Nacional de La Rioja; National Museum of Natural History, Smithsonian Institution
Thanks for your time!!