Name: 1 GEOL 104 Dinosaurs: A Natural History Homework 6: The Cretaceous-Tertiary Extinction DUE: Fri. Dec. 8 Part I: Victims and Survivors Below is a list of various taxa. Indicate (by letter) if the taxon: A. Was already extinct by the Cretaceous-Tertiary Boundary X. Died out at the Cretaceous-Tertiary Boundary S. Survived the Cretaceous-Tertiary Boundary (although it may have died out subsequently) 1) Inoceramids 2) Ammonoids 3) Plesiosaurs 4) Ichthyosaurs 5) Placentals 6) Rudists 7) Multituberculates 8) Champsosaurs 9) Coccolithophorids 10) Pterosaurs 11) Ornithischia Extra Credit) Saurischia Part II: Causal Agents and Physical Evidence There are three environmental changes at or near the K/T boundary that might have had the potential to produce the extinction events. These three potential causal agents were introduced in class, but here they are again: • Chicxulub Impact: collision of a 10-15 km asteroid with the Earth at 65.5 Ma, blasting an enormous volume of ash and dust into the atmosphere. Expected effects: o Blotted out sunlight, stopping photosynthesis on land and sea, causing starvation of herbivores, causing starvation of carnivores o Possibly other short-term effects (blast wave, increased acid rain, wildfires, etc.) o Immediate effects would be very intense but very short term (< 1 day to a year or less) • Deccan Traps Volcanism: eruption of vast lava fields in western India starting around 66 Ma, and lasting for a million years or less, sending huge amounts of ash and dust into atmosphere. Expected effects: o Blotted out sunlight, stopping photosynthesis on land and sea, causing starvation of herbivores, causing starvation of carnivores o Possibly also increased amounts of various pollutants into atmosphere o Immediate effects would be intense and extend over hundreds of thousands of years prior to K/T boundary • Maastrichtian Regression: huge drop in global sea levels, exposing large areas of land previously submerged, starting around 69 Ma and ending around 65 Ma. Expected effects: o Change planetary albedo (reflectivity), changing both amount of heat absorbed by Earth and that heat’s distribution o Change in oceanic circulation patterns o Decrease in oceanic productivity (how much nutrients are produced) because of loss of warm shallow seas o Increase in continentality of climate (more intense summers and winters) o Immediate effects would be gradual and extend over millions of yearsName: 2 These different causal agents would leave different types of records in the rocks. For each of the questions below, circle the appropriate answer as to which causal agent(s) (Asteroid Impact, Deccan Traps Volcanism, or Maastrichtian Regression) would leave such a record. 12) Ash from very short term but global forest fires: A. Asteroid Impact B. Deccan Traps Volcanism C. Maastrichtian Regression D. A & B, but not C E. A, B & C 13) Replacement of one set of plant fossils over the last several million years of the Cretaceous: A. Asteroid Impact B. Deccan Traps Volcanism C. Maastrichtian Regression D. A & B, but not C E. A, B & C 14) Iridium spike: A. Asteroid Impact B. Deccan Traps Volcanism C. Maastrichtian Regression D. A & B, but not C E. A, B & C 15) Chemical evidence for decreased amount of photosynthetic activity (indicating reduction in sunlight): A. Asteroid Impact B. Deccan Traps Volcanism C. Maastrichtian Regression D. A & B, but not C E. A, B & C 16) Tsunami deposits on the Atlantic & Gulf Coasts of the Americas: A. Asteroid Impact B. Deccan Traps Volcanism C. Maastrichtian Regression D. A & B, but not C E. A, B & C 17) Extensive lava flows in India: A. Asteroid Impact B. Deccan Traps Volcanism C. Maastrichtian Regression D. A & B, but not C E. A, B & C 18) Shocked quartz: A. Asteroid Impact B. Deccan Traps Volcanism C. Maastrichtian Regression D. A & B, but not C E. A, B & C Extra Credit) All of these three agents would have had global effects. However, two of them would have DIRECT evidence over much of the world, while one would have direct physical evidence that was much more limited in its coverage. Which one would have the most restricted coverage? [ Asteroid Impact | Deccan Traps | Maastrichtian Regression ] (Circle)Name: 3 Part III: K/T Extinction Patterns in the Terrestrial Realm Let’s look at the patterns of extinctions at the K/T boundary for major clades of terrestrial vertebrates, with emphasis on dinosaurian clades. For each taxon the diet, the adult size, and the likely physiology (warm- or cold-blooded) are listed. (Note that sizes of the late Maastrichtian representatives are shown: earlier or later representatives may have been larger). Survivors Taxon Habitat Adult Size (kg) Physiology Aves (various lineages) Flying <1 – 5 (most <1) Warm Crocodilians (various lineages) Semi-aquatic ~10 – 50+ Cold Champsosaurs Semi-aquatic 10 – 25 Cold Lepidosaurs (lizards and snakes) Land <1 – 10 (most <1) Cold Turtles Land & semi-aquatic <1 – 10 Cold Mammals (various lineages) Land <1 – 5 (most <1) Warm Amphibians Semi-aquatic <1 Cold Victims Taxon Habitat Adult Size (kg) Physiology Ichthyornithiform birds Flying <1 – 3 (most <1) Warm Enantiornithine birds Flying <1 – 5 (most <1) Warm Deinonychosauria Land 10 Warm Oviraptorosauria Land 10 – 175 Warm Therizinosauroidea Land 500 – 3000 Warm Alvarezsauridae Land 1 – 5 Warm Ornithomimosauria Land 175 Warm Tyrannosauridae Land 6000 Warm Abelisauroidea Land 5 – 3000 Warm Titanosauria Land 30,000 Warm Ceratopsidae Land 6000 Warm Leptoceratopsidae (ceratopsians) Land 100 Warm Pachycephalosauria Land 200 Warm Hadrosauridae Land 6000 Warm Thescelosauridae (ornithopods) Land 90 Warm Rhabdodontidae (ornithopods) Land 150 Warm Ankylosauridae Land 3000 Warm Nodosauridae Land 2500 Warm Pterosauria Flying 5 – 200 WarmName: 4 19) Many scientists have said that there is a strong size bias in survivors vs. victims in the K/T boundary on land. Look at the data on the previous page. In general, the majority of the survivor groups are [ smaller | the same size | larger ] than the majority of the victims 20) Semi-aquatic animals [ mostly became extinct | mostly survived ] the K/T extinction. 21) Compare the list of survivors and victims. [ Warm-blooded | Cold-blooded ] animals tended to survive better