Lecture 7 - Dinosaur Ancestry

Question 1

tetrapods

Answer 1

4 limbed animals

Question 2

vestigial structures

Answer 2

structures that had a use before but are now just reminents of that structure

eg tail bone, arms in snakes

Question 3

where did tetrapods evolve from?

Answer 3

lobe finned fish

articulated bones in their fins (hands)

have gills AND lungs

Question 4

when did reptiles evolve?

Answer 4

late paleozoic, amphibian ancestry

Question 5

what are the key evolutionary novelties of REPTILES?

Answer 5

amniotic egg (hard shelled eggs ON LAND; allowed oxygen in, waste air out, but NOT FLUID)

more robust skeletons that supported movement on ground

Question 6

how many clades do tetrapods have?

Answer 6

TWO clades, with one being

NON-AMNIOTIC AMPHIBIANS and the other being AMNIOTES

Question 7

why is “reptile” not accurate?

Answer 7

bc it is a paraphyletic group unless we include all other descendents like mammals and birds

Question 8

4 classifications of reptiles

Answer 8

anapsid (no fenestra)

euryapsid (1 upper fenestra)

synapsid (1 lower fenestra)

diapsid (2 fenestra)

Question 9

fenestra

Answer 9

openings behind the eye socket (orbits)

Question 10

lepidosaurs

Answer 10

diapsid reptiles

divided into one clade, which leads to modern lizards and snakes

Question 11

archosaurs

Answer 11

a clade that leads to dinos and pterosaurs and crocs

Question 12

immediate dino ancestor

Answer 12

semi upright (bipedal) meat eater

Question 13

what are the steps in tetrapod evolution leading to archosaurs?

Answer 13

lobe-finned fish

amphibians

reptiles

diapsid reptiles

dinos