Lecture 16: Dinosaurs: tiddlers and titans Flashcards Preview

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1
Q

Dinosaur eggs

A

very distinctive microstructure
largest sauropod ~40 m long & 100 tonnes
largest egg: ~ 5.5 litres (‘football’)
amniotic egg

2
Q

why so “small” eggs?

A

Shell thickness- bigger egg is, the thicker the shell- embryo would need to be able to get through
Gas diffusion- too thick a shell would mean inability

3
Q

How did they lay their eggs?

A

Squatting down?
ovipositor?
no real evidence…

4
Q

Baby factories?

A
12-100 eggs per year
 40-year old dinosaur ~450-4,000 eggs/lifetime
generally ‘r-strategists’
lots of young, little care
high mortality?
large mammals, e.g., elephant
~12 young/lifetime
‘K-strategists’
few young, lots of care
low mortality
5
Q

Implications for dinosaurs?

A
rapid reproduction
rapid growth
many juveniles, few adults
expand population rapidly
cope with environmental change
6
Q

Orodromeus eggs

A

eggs in spirals
large, irregular eggshell fragments
babies’ joints well formed (could fend and walk themselves immediately)
“precocial” offspring

7
Q

Hadrosaur Maiasaura eggs

A
Bowl-shaped nests
Eggshell fragments small
Juveniles 8-9 months old
Worn teeth
"altrichial” offspring- not ready to fend for themselves.
8
Q

What suggested the dinosaurs were coming back to same places to lay eggs?

A
several nests on one horizon
evenly spaced
nested in large groups/herds
successive layers of nests in sequence
annual breeding
complex social behaviour
9
Q

Cold or warm blooded?

A

Reptiles are ectothermic

Use sun

10
Q

You are what you eat..?

A

endotherms consume more food
endotherms require >10x more food as ectotherms of same body mass
look at population structure

11
Q

Predator : prey ratios

A

10-60% in modern and ancient reptiles
1-4% in modern and ancient mammals
dinosaurs: 0.5-3.5%

12
Q

Large sauropods dimensions (Sa:vol)

A

volume increases more than surface area
slow heat loss
“mass homeothermy”

13
Q

Dinosaurs with feathers…?

A
...but symmetrical feathers
therefore not for flight…
insulation?
foraging?
display?
14
Q

Did flight evolve “ground up”?

A
ground-dwelling ancestor
feathers for insulation?
feathers used for trapping prey
leaping 
flying
15
Q

Or did flight evolve “trees down”?

A
arboreal ancestor
feathers for insulation?
glided from tree to tree
feathers became asymmetrical
flying
16
Q

Votes for “ground up”?

A

dinosaurs with “non-feather” filaments
insulation
dinosaurs with symmetrical (i.e., non-flight) feathers
flight evolved later…

17
Q

Votes for “trees down”?

A
Microraptor
smallest non-bird theropod dinosaur known
would fit in palm of hand
small enough to have lived in trees
symmetrical feathers
glider?