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GEOL 240 The Dinosaurs: Introduction. Summary. What is a fossil? The science of taphonomy How it works. What is a Fossil. (from Latin fossilium "that which is dug up") are the physical remains of past life and its activities preserved in the rock record.
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Summary • What is a fossil? • The science of taphonomy • How it works
What is a Fossil • (from Latin fossilium "that which is dug up") are the physical remains of past life and its activities preserved in the rock record. • The only physical evidence of ancient organisms. Only direct data for knowledge of past life • Paleontology, the study of ancient life and their remains (fossils). • Vertebrate Paleontology, the study of ancient backboned animals, including dinosaurs
Types of Dinosaur Fossils • Isolated bones and teeth • Skeletons, in varying degrees of completeness • Footprints and trackways • Skin impressions and Feathers • Mineralized soft tissue (muscles, intestines, possible heart) • Eggs (some with embryos) and nests • Coprolites (fossilized feces) Trace Body
Taphonomy taphos = “burial” + nomous = “law” The study of how fossils are formed. The scope of taphonomic research can be conveniently summarized as: • The manner and cause of death of organisms • Processes of decay and decomposition • Transportation of fossils or potential fossils • Burial of remains • Diagenesis (conversion into rock) of remains
The Importance Of Bones The Data:
Removing the Bones carrying bones out of the desert documenting bones in Big Bend Some bones require cranes and trucks to move them
Preparing The Bones Collections area and bones carefully removing fossils from large blocks of rock. Windows to the Prep Lab let you watch preparators work.
Reconstructing The Skeletons Aligning sauropod vertebrae (Source: http://www.mwc.mus.co.us/dinosaurs) Measuring sauropod limb bones Reconstructed dinosaur skeletons on display at the Smithsonian Museum
Developing The Story Artist’s idea of how the Cretaceous might have looked. Life-sized reconstruction of T. rex’s left hind leg with foot skeleton. Bones from the Big Bend site were deposited in “an ancient riverbed.”
Plant/Animal Fossils Turtle fossil from Green River Fm. Sandstone slab with more than 520 fresh-water herring from Green River Fm. Petrified trees are also found at the dig site.
Tracks This theropod track is in the Morrison Formation (Jurassic) of eastern Utah. Notice the greater depth of the track in the toe region, which suggests a horizontal posture for the dinosaur while it was walking. Trackway with 2 sets of prints: Iguanadon and Megolasaurus. (Source: http://www.stone.uk.com/dinos/) Iguanodont track, left, compared to a meat-eating dinosaur track.
Teethmarks Tyrannosaurus rex skull. One can see there is considerable “bite potential” in these large carnivorous teeth. The end of this limb bone from Apatosaurus has parallel toothmarks on it. The spacing of the tooth marks, as well as the individual marks themselves, help to identify what dinosaur was feeding on this apatosaur.
Gastroliths These could be gastroliths (dinosaur gizzard stones used in some birds to aid in grinding up food), or they could be just polished stones. One of the major criteria for suspecting gastroliths in this case is that these specimens were found in Mesozoic rocks that were known to contain dinosaurs. In a few cases a pile of similar stones has been found within the ribcage of a dinosaur. That is a more serious criterion.
Coprolites This coprolite on the left has been attributed to Tyrannosaurus and is half a meter long. The one on the right is ascribed to a hadrosaur…whether they are correctly attributed or even correctly designated is just a guess
Eggs & Nests One of the more spectacular dinosaur fossil finds of recent years was of a Late Cretaceous specimen of Oviraptor that was found in a sitting position directly overa nest. This find, a wonderful combination of trace fossils and a body fossil, represents one of the most compelling pieces of evidence for brooding behavior in dinosaurs. It could, of course be explained otherwise. This fossil find is currently on display at the American Museum of Natural History in New York and was illustrated in a National Geographic article.
Skin This model at Dinosaur Valley provides an idea of how dinosaurs might have looked. A natural cast of the skin of a hadrosaurian dinosaur, preserved in sandstone. The skin had a pebbled structure and appears to have been devoid of scales.
Artistic Rendition “The World of Dinosaurs” Commemorative Stamps Sketch of Allosaurus
Animated Models Full-sized Tyrannosarus rex head, purchased from the Dynamation company which makes robotic dinosaurs. The skin, and the color, of course, are an artistic and scientific guess. Fully robotic Allosaurus Fragilis created for the McKinley Museum of Science and History in Ohio. Cut-away shows inner workings of pneumatic system. (Source: www.panix.com/~spoerri)
Famous Dinosaurs Dino Godzilla Jurassic Park (Source: www.tbssuperstation.com) Gertie Barney & Company (Source: www.dinosaur.org/Gertie6.htm)
Dinosaur Myths • Dinosaurs represent failure & extinction. • Dinosaurs and humans. • Dinosaurs were either all hot-blooded or all cold-blooded. • The word dinosaur means “terrible-lizard”. • Whatever you read in the latest “dinosaur book” must be true. • Dinosaurs all died at the same time. • Mammals arose after the dinosaurs, and helped drive the dinosaurs into extinction by eating dinosaur eggs. • An asteroid (or comet) killed the dinosaurs. • All big reptiles from the prehistoric past [“Monsters”] are dinosaurs. • Archaeologists dig up dinosaurs.
Quick Course in Geology • Because fossils are preserved in rock, need to understand basics of geology. • Rocks (naturally occurring cohesive solids comprised of one or more minerals or mineraloids) are generated in one of three primary manners (basis of rock classification): • Igneous • Metamorphic • Sedimentary
Rock Types IGNEOUS SEDIMENTARY METAMORPHIC
Igneous Rocks Igneous rocks form when molten rock (magma) originating from deep within the Earth solidifies forming distinct crystals of different minerals. The chemical composition of the magma and its cooling rate determine the final igneous rock type. Extrusive (erupts to surface) Intrusive (within the Earth)
Metamorphic Rocks • Metamorphic rocks are rocks that have been substantially changed from their original igneous, sedimentary, or earlier metamorphic form. • Metamorphic rocks form when rocks are subjected to high heat, high pressure, hot mineral-rich fluids or, more commonly, some combination of these factors. BUT THEY ARE NOT MELTED DURING THE METAMORPHIC PROCESS
Sedimentary Rocks • Sedimentary rocks are formed from pre-existing rocks (sediment) and/or pieces of once-living organisms. They form from deposits that accumulate on the Earth’s surface as a result of transport and settling of sediment which then becomes compacted to form rock layers.
Clastic Sediment • Formed of fragments of weathered rocks or ash/dust - Sand, clay, & boulders are examples. • Clastic sedimentary rocks are named according to the sizes of the particles. • Clast = Greek for “fragment” or “piece”
Clastic Sediment • Formed of fragments of weathered rocks or shells - Sand, clay, boulders and shell fragments are examples. • Clastic sedimentary rocks are named according to the sizes of the particles. Conglomerate Sandstone Siltstone Shale (clay)
Chemical Sedimentary Rocks • “Chemical” sedimentary rocks are often assumed to have formed by chemical precipitation. The process is visualized as beginning with water traveling over or through rock, dissolving some of the minerals and carrying them away from their source. Eventually these minerals are thought to have precipitated when the water evaporates away or when the water becomes over-saturated. Other origins appear to be probable.
Examples: “Evaporites” Gypsum (CaSO4 • 2H2O) and Halite (NaCl) Gypsum is sometimes formed by the evaporation of seawater rich in calcium - it forms after limestone and before halite
Biologic Sedimentary Rocks • Biologic sedimentary rocks form from once-living organisms. They may form from accumulated carbon-rich plant material (coal) or from deposits of animal shells. • Limestone & dolomite are often composed in part or in whole of the shells and other hard body parts of marine organisms such as clams, coral, oysters, and microscopic organisms like diatoms that have been transported and deposited as sediment, then hardened into rock
Sedimentary Environments • Uniformitarian assumption • Marine - Ocean/Sea • Non-marine (or terrestrial) • fluvial • lacustrine • eolian • deltaic
