SPU-22: The Unity of Science from the Big Bang to the Brontosaurus and Beyond

1. SPU-22: The Unity of Science from the Big Bang to the Brontosaurus and Beyond Lecture 16 2 April 2014 Science Center Lecture Hall A

2. Outline: … Fossils and Dinosaurs Early history of fossil discovery concluded Detailed study of biggest dinosaurs of them all: Sauropods This is dinosaur day. Sit back and enjoy

3. Mary Anning(?) (1799-1847)

4. Sullivan (1908) on Anning She sells seashells on the seashoreThe shells she sells are seashells, I'm sureSo if she sells seashells on the seashoreThen I'm sure she sells seashore shells

5. Gideon Mantell (1790-1852)

6. Iguanodon Skull

7. Dinosaurs Named for “terrible lizard” by Richard Owen (1842) Fossils actively sought since: Now found on all six continents including Antarctica (how come?) We will concentrate mainly on sauropods. Why? (See next slide plus four.)

8. Richard Owen (1804-1892)

9. First Full-Scale Dinosaur Fossil Found Of all places: New Jersey

10. Location of First (Nearly) Complete Dinosaur Fossil Found: Haddonfield, New Jersey

11. First Mounted Dinosaur(From Haddonfield, NJ, Discovery)

12. Classification Of Dinosaurs Theropods: Tyrannosaurus Rex; Birds Sauropods: Largest creatures ever to roam earth Note: Big business for paleontologists Glory promotes “over discovery” (e.g., brontosaurus vs. apatosaurus; what is a species, anyway? Also, see next slide.)

13. Note On Classifications Classification of organisms is big business. There are two main systems: The old, familiar one (kingdom, phylum, class, order, family, genus species), and the (relatively) new one of cladistics (clade contains all organisms which have one unique characteristic in common) We avoid discussion of classifications for most part, minding our own business instead

14. Naming of Dinosaur Species: Numbers Game We decline to play: Too arbitrary, too complicated, and too long an adventure before gaining any reward via understanding

15. Sauropod (= Lizard Foot) What do we want to know? - When appeared? • What sizes and why so big? • Where lived? • Locomotion? - Why shaped as is? • Warm- or cold-blooded? • Diet? What eat? How eat? - Diseases? • Life cycle? (birth, parental care, rate of growth) • Populations?

16. What Sizes And Why So Big? Fossil bones establish gigantism, and range of (large) sizes of sauropods (see next three slides for rather large examples and following three for purported time changes) Models to “explain” size, answer question why so big: • Grew to be more predator resistant; allowed by large available areas; helps food processing; Cope’s “rule”; Evolutionary Cascade Model (complicated; see next slide plus six)

17. Most Complete Sauropod Fossil(Berlin Museum)

18. Apatosaurus: ~ 80% Complete(150 Mya, Wyoming, ~25 m long)

19. Large Sauropod (“Reconstructed”)

20. Evolution Of Size Size of dinosaurs (and other species, e.g., humans) seems to increase with time: Cope’s (late 19th century) Rule Why? Some suggested potential (and some actual) benefits: defense against predators; success in predation; more success in mating; increased intelligence; increased longevity; increased thermal inertia; increased survival through lean times

21. Evolution Of Size (Concluded) What limits size growth? Some possible contributing factors: increased requirements for food and water; increased susceptibility for extinction (e.g., increased development time of individuals implies longer generation time and slower adaptation to environmental change); lower fecundity; and physics constraints How reliable is Cope’s Rule? “Controversial”

22. Size History of Sauropods (Infamous) plot – see next slide Follow-up attempts Current status of same

23. Carpenter’s 2006 Figure: Purported Sauropod Size Proxy Vs. Time

24. Evolutionary Cascade Model

25. Where Lived? Land or water habitat? • Land wins; pressure, e.g., at 10 meter depth, apparently enough to collapse lungs and cause heart failure • However, fossils, especially of juveniles, usually found near where water had been (of course, needed to drink)

26. Locomotion? How did sauropods move? How fast? How long (endurance)? Dependence on size? Very basic, but difficult questions to answer Evidence: Bathtub-sized tracks of some fossils; distinguish juveniles from adults (former seemed to preferentially live near shores -- see birth-place choices); upright gait (when developed?); front and hind limb tracks imply pace length, hip height, walked on “all fours;” computer simulations to compare…

27. Why Shaped As Is? Small head and long neck: Allows reaching more food easily. Can’t lift combination if too heavy; neck bones hollow (conduct air) to make lighter, and food (see below) not masticated to keep mouth small Big body: Anchor neck and tail; process (lot of) food Long tail: Help balance; protect against predators; snap like whip (make scary noise)

28. Warm- Or Cold-Blooded? Not easy to answer: Try to distinguish via isotope measurements (see next two slides) Problem with fully grown sauropods cooling: recall area-to-volume issue in shedding heat

29. Possible Proxy For Body Temperature Chemical in bones – bioapatite (don’t even think of asking!) – appears to have potential as proxy for temperature of host organism How does it work? “Preference” for certain isotopes of carbon and oxygen, two of elements in bioapatite, to bond with each other in its crystal lattice Key point: This bonding is temperature dependent Key Question: Can this dependence be reliably measured and calibrated? Tested on contemporary creatures and 12 Myr old fossils

30. Temperature Proxy (Concluded) So far so good: What about sauropods? Recent work yielded temperatures 36 – 38 deg C., similar to those of most modern mammals, including us. Warm vs. cold blood: Case closed? Nope. We still cannot reliably distinguish between warm and cold blood, because we do not know other heat-control mechanisms that sauropods might have utilized. (Keep in mind, too: Bigger organism, harder to cool due to area-volume problem.) Moral: Science usually advances incrementally; herein a shining example of very innovative approach that may – or may not – be an important step in long run

31. Diet: What Eat? How eat? What: Herbivores or carnivores (or both)? - Examine teeth (see next five slides); adults are herbivores; juveniles may be both (need to grow fast; see below) How: Move head sideways or vertically, too? - Unclear, though moving head vertically may cost lot of energy What fraction of time spent eating? Large!

32. Herbivores Vs. Carnivores How do we know diets of dinosaurs? Mostly inference from teeth (see next five slides) Relations between flora, fauna, diet, and size: Did, e.g., herbivore diet precede or follow large size and four-footedness? No one knows. Do know that herbivores require much more food than carnivores. What fraction of sauropods were low browsers (suitably defined) and what fraction high browsers? How varied with time? Same answer as for first question

33. Sauropod Teeth

34. Giraffe Teeth

35. Tyrranosaurus Rex Teeth

36. Lion Teeth

37. Tooth Replacement Replacement rates vary: roughly one new tooth every ~35 days or one new tooth every ~60 days, depending, respectively, on whether low- to mid-canopy browsers or mid- to high-canopy browsers. Why? Probably more grit on food closer to ground

38. Diseases? Nothing is reliably known about dinosaur diseases

39. Life Cycle? What is “born”? Eggs; often large clutch (see next two slides) Parental care? Probably small (too many; too “clumsy”?) ; don’t know How grow? Enormously: ~10 to ~50,000 kg; fast at start; 10 - 20 years to sexual maturity; 30 (?) years to full adult size. Different basic metabolic rate (BMR) as grow to and then from adulthood? Lifetime maybe >100 years??

40. Clutch Of Sauropod Eggs From Find In Argentina

41. Dinosaur Egg

42. Lifetimes? Not much is reliably known about dinosaur lifetimes; all by inference: Analogy with birds (e.g., swans, parrots for long lives), and crocodiles and tortoises. Many species may have had individuals with life-spans generally of order 100 years (note decades to maturity)

43. Populations? Where did dinosaurs live? Fossil tracks found so far on all continents, as earlier noted How many lived in each location as function of time? Your guess is as good as mine. But female sauropods did gather at least once to same place in Argentina to lay clutches of eggs

44. What Have We Learned? Tremendous amount about characteristics of sauropods Lot about (often multiple) models for each characteristic Models are speculations; we’re short on verifications