Lesson 18 - Origin of Dinosauria

Question 1

are pterosaurs dinosaurs

Answer 1

no

Question 2

what makes the 2 lineages of archosaurs distinct

Answer 2

ankle joint
– ankle of the crocodyliant joint is between the astralagus and the tarsals (calcaneous is below the joint)
— allows crocs to walk with splayed or tucked feet –> can twist food sideqays
– the ankle joint in the avimetatosalia –> the calcaneus is above the joint
— cannot twist food sideways

Question 3

how many times did powered fligth evolve in the aurnothidyria

Answer 3

twice – pterosaurs and birds

Question 4

presence of perforated acetabulum

Answer 4

• the socket that recieves femoral head
• is perforated
• is a synaptomorphy of dinosauria

Question 5

pterosaur

Answer 5

• wing formation is different from birds
• pterosaurs occupy different niches than what birds did at that time
• suggests that the birds and pterosaurs were probably not in competition
• evidence suggests that they coexisted

Question 6

key synaptomorphy of dinosauris

Answer 6

• ankle joint

Question 7

ankle joint for an anigator crocodyloid joint

Answer 7

• the astragalus and fibula are on the proximal side of the ankle joint
• the calcaneus and distal tarsals are on the distal side of the ankle joint (basically the calcaneus is below the joint)
  ^^^ once again why they can walk with the their foot splayed to the side or underneath

Question 8

ankle joint for lesothaurus

Answer 8

• the astralagus and calcaneus are the proximal tarsal bones
• the ankle joint passes between the proximal and distal tarsal bones (calacneus above the joint)

Question 9

pterosaurs + dinosaurs =

Answer 9

avemototarsilia
- decoupling for the fore and hindlimbs
- bipedalisma and the quadrapedalism evolved a lot in the group

Question 10

why is it likely that bipedalism is ancestral for avemmototarsilia

Answer 10

the presence of metatarsals

Question 11

how many times did powered flight evolve in the ornithidira

Answer 11

twice

Question 12

just because they are dinosauromorpha…..

Answer 12

does not mean that they are dinosaurs

Question 13

synapomorphy of dinosauromorha

Answer 13

• offset femoral head
  —- provides a more upright stance
  —- rotated hindlimb

Question 14

pterosaur wing support

Answer 14

support of wing is skeletal – it is the digits

Question 15

commonalities between pterosaurs and birds

Answer 15

• presence of hollow long bones
• well developed sternum
• some, not all pterosaurs lost their teeth and developed beaks (like birds)

Question 16

ornithidires

Answer 16

• early one had an erect stance?
• post cranial numitization (hollowed out bones)
• bones are usually strutted
  ^^^^ cross sectional bony material placed every so often to provide strength
• traces of air sacs

Question 17

for ornithidires - what does the presence of air sacs and numitization suggest

Answer 17

that they had flow through ventilation

Question 18

basal archosaurs

Answer 18

• had a kind of sprawling crawl
• humerous and the femur extended horizontally
  ^^^^^ not in the case for dinosaurs (had to be a change in order to get so large) —- selection for movement of limbs to move underneath the body

Question 19

ornothricia

Answer 19

• ancestral state is bipedalism
• quadrupedalism evolved 4 times

Question 20

thyreophora

Answer 20

• include stegosaurs
• big dorsal spikes/plates along the ventral column (reason for these is up for question)

Question 21

dorsal spikes/plates of thyreophora

Answer 21

• known for careful analusis of many fossil specimins that these plats were indeed vasularized
  (thermoregulation) –» if they could control that blood flow

Question 22

serotopsians

Answer 22

• made from an enlargement of the parietal and squamosal bones
• many have a clear beak-like structure – similar to a parrot
• evolved from a bipedal ancestor

Question 23

ornithopods

Answer 23

• mostly fairly small – from 1 to 2 meters
• bipedal
• hadrosaurs

Question 24

hadrosaurs

Answer 24

3 kinds
- hollow crested
—- air delivered up the passage up then back to the naris
—- might have made a resonating sound for a form of communication
—- flat headed
—- solid-crested
—– quite social –> maybe some degree of parental care (found fossils of males hanging out with young)

Question 25

orthinians and social behavior

Answer 25

• lots of evidence that the brooding of eggs occurred (incubation)
• fossilized adult ornothicians around a clutch of eggs
• fossilized specimens of babies suggested an altricial development
• ear morphology
  —— suggesting that juvoniles could be detected from their high pitch voices

Question 26

saurischia

Answer 26

• quadrapedal herbivores
• extremely large
• comes from the very massive vertebrae
• very strong limbs coming out of vertebrae
• bending like forces transformed to compression forces
• ## diplodocoid

Question 27

diplodocoid

Answer 27

• 60% tail, 15% trunk, 25% head and neck
• maybe long necks have access to higher up foliage
  — DOWNSIDES
• holding head for that long over the body would require a verys trong heart and very high blood pressure in order to maintain head above the body for that long
  SEXUAL THINGS
• maybe use long necks for fighting
  TAIL
• probably used as a counterbalance
• defense - tail -whippinh
• tactile function
  —- feel where others were nearby