week 5

Question 1

did all dinosaurs have the amniotic egg? what evidence do we have to suggest for/against?

Answer 1

all dinos came from an amniotic egg, as the ancestor had one

Question 2

what are some benefits to an amniotic egg?

Answer 2

can colonize terrestrial environments where there is less water to lay eggs
also it’s a protected environment for the dino fetus to develop

Question 3

do we mammals have amniotic eggs?

Answer 3

yes, we just don’t lay them externally

Question 4

true or false: to protect the egg, eggs are completely sealed off from the environment

Answer 4

false

eggs allow for the transfer of oxygen and carbon dioxide through tiny pores

Question 5

bigger dino = bigger egg. yes? no? thoughts?

Answer 5

eggs could only get so big (cube-square law)

if the egg got too big, the oxygen requirements within the egg would become greater than the surface area that can transfer oxygen across

Question 6

dinos are not the same size as they are when they are born. what evidence do we have of their growth?

Answer 6

looking at bone histology

every year, osteons get added to the bone’s outer wall
–> when resources are short in supply, there’s a LINE OF ARRESTED GROWTH

Question 7

what are the characteristics of dino bones as they age?

Answer 7

younger: highly vascularized and “lamellar”

middle age: remodeling, where once baby bones are fully developed they get replaced w newer bones (HAVERSIAN)

old: EXTERNAL FUNDAMENTAL SYSTEM (indicates growth is done)

Question 8

what is an ontogenetic change? what is an animal that has it? one that doesn’t?

Answer 8

ontogenetic changes are developments post birth (ex. toddlers have bigger eyes etc than adults)

Question 9

what is an ontogenetic change that occurs in hadrosaurs?

Answer 9

development of the beak

Question 10

what is an ontogenetic change that occurs in ankylosaurs?

Answer 10

development of armour + tail club

Question 11

what are isometric and nonisometric changes? list some important examples

Answer 11

isometric: change in size but no relative proportions

–> nonisometric changes: change in relative proportions

isometric: idk

nonisometric: t-rex tibia is much longer than femur in juveniles, but the femur grows to be the same sizee

Question 12

what is sexual dimorphism

Answer 12

male and female look different

Question 13

were proceratops sexually dimorphic? what are the arguments for/against?

Answer 13

for: some indiv have wider frills even though head and body are the same size

against: could just be circumstantial - longer the indiv lives, the bigger the frills grow?

Question 14

was there a lot of egg protecting/rearing for dinos?

Answer 14

+ we see lots of dinos dead in their nests

• what if the dino was eating the eggs and got fucked
• bones might have been washed into the nest

Question 15

what is a novel approach we are taking to looking at sex in dinos

Answer 15

the medullary bone

when female dinos are getting ready to lay eggs, they need a lot of calcium. instead of taking [], they develop the medullary bone and devote that bone solely to a calcium reserve

problem: only developed in female dinos that were actively preparing to reproduce (not in young, or if the dino just wasn’t getting ready to reprod)

Question 16

what is the medullary bone?

Answer 16

calcium store for when female dinos were getting ready to lay eggs

Question 17

did big sauropods raise their young?

Answer 17

no - they laid them in big communal nesting grounds, which would make it virtually impossible to reach their egg without stepping on another dino’s egg.

instead they abandoned the nesting ground and relied on predator satiation (ie that there were so many eggs, the predator would be satiated and wouldn’t eat all the eggs)

Question 18

who did the largest dino egg belong to?

Answer 18

oviraptorsaurids

Question 19

how could we identify baby chasmosaurs from adults?

Answer 19

• had same skin impressions as adults
• had larger orbits

Question 20

sauropods are similar to what animal in terms of nesting?

Answer 20

sea turtles

Question 21

how are confuciusornis thought to have exhibited sexual dimorphism? from where do we make these inferences?

Answer 21

males were thought to have long tail feathers while females had no tial feathers. this sort of ornate dimorphism is exhibited in present day birds

Question 22

where does the calcium meant for eggshells come from? the blood stream, the bones, or from food?

Answer 22

from the bones

while the dino may get calcium from blood/food, any calcium that is meant for eggs will be stored in the medullary bones (blood/food –> bones –> egg)

Question 23

where are the medullary bones found?

Answer 23

in marrow cavities in bones

Question 24

how did dinosaurs fertilize their egg

Answer 24

we think internally…. but we dk how……….. (they were fuckin………………….)