Loading in 2 Seconds...
Loading in 2 Seconds...
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. Outline: … Fossils and Dinosaurs.
2 April 2014
Science Center Lecture Hall A
Early history of fossil discovery concluded
Detailed study of biggest dinosaurs of them all:
This is dinosaur day. Sit back and enjoy
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
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.)
Of all places: New Jersey
Theropods: Tyrannosaurus Rex;
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.)
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
We decline to play: Too arbitrary, too complicated, and too long an adventure before gaining any reward via understanding
What do we want to know?
- When appeared?
- Why shaped as is?
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:
by large available areas; helps food
processing; Cope’s “rule”; Evolutionary
Cascade Model (complicated; see next
slide plus six)
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
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”
(Infamous) plot – see next slide
Current status of same
Land or water habitat?
apparently enough to collapse lungs and
cause heart failure
found near where water had been (of course,
needed to drink)
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…
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)
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
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
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
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!
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
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
Nothing is reliably known about dinosaur diseases
What is “born”? Eggs; often large clutch (see next
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??
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)
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
Tremendous amount about characteristics of sauropods
Lot about (often multiple) models for each characteristic
Models are speculations; we’re short on verifications