Chapter 28 - Reptiles

Notes for Chapter 28: Reptiles

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or back to Chapter 27
or ahead to Chapter 30

Chapter 28 Assignment: 559-571, 576-579; RQ-28: 2-5, 7, 10, 16-17
Then: Ch. 30: 609-621, 624-626, 634-639;
RQ-30: 1-2, 6-8, 11, 15-16 (last two lectures)

Introduction: Enclosing the Pond

Source of Image Source of Image

Featured Animal: Komodo lizard (Komodo dragon)
More Links: 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9

The amnion and amniotic egg

Frog: Lizard:

many eggs laid in water Fewer eggs laid on land

fully aquatic larval stage no larval stage

metamorphosis to develops directly to
juvenile juvenile

sexually mature adult sexually mature adult
mates in water mates on land

external fertilization copulation

amniotic egg - embryo plus extraembryonic layers
(see pp. 171-172)

amnion is fluid-filled sac that protects embryo

yolk sac provides food

allantois gathers waste

chorion surrounds all the other layers

egg is enclosed in semi-permeable shell

Leading hypothesis of amniote relationships
(see cladogram Fig. 28-2)

Amniota
   Synapsida
      various extinct lineages
      Mammalia
   Sauropsida (or Reptilia w/ birds included)
      turtles (although molecular studies suggest archosaur affinities)
      Diapsida
          Lepidosauria
             Sphenodon (the tuatara)
             squamates (lizards incl. snakes)
             various extinct marine reptiles such as ichthyosaurs
          Archosauria
              crocodiles
              pterosaurs, dinosaurs (incl. birds)

Next lecture:

Dinomyths
1. Dinosaurs are big lizards
2. Dinosaurs were all big extinct reptiles
3. Dinosaurs had a sprawling stance
4. Dinosaurs were all big
5. The largest dinosaurs lived in swamps
6. T. rex ate Brachiosaurus
7. Dinosaurs dragged their tail
8. Dinosaurs were cold-blooded and sluggish
9. Dinosaurs were stupid
10. Dinosaurs went extinct

1. Dinosaurs are big lizards
   actually are closer to crocodiles
   think birds (see cladogram on p. 585)

2. Dinosaurs were all big extinct reptiles
   pterosaurs are sister taxon of dinosaurs
   ichthyosaurs, etc. are nearer to lizards
   pelycosaurs (e.g., Dimetridon) are nearer to mammals

3. Dinosaurs had a sprawling stance
   instead had fully upright stance
   synapomorphy: hip socket has central hole,
   hind limbs directly under body, swing fore-aft
   (other archosaurs have solid hip socket and sprawling stance)
   not necessarily faster, but better endurance
   because movement doesn't constrict the lungs

4. Dinosaurs were all big
earliest dinos (240 mya) were small
more recent dinos as small as hummingbirds

5. The largest dinosaurs could only support their body weight in swamps
an elephant would sink in the mud
more likely lived in savanna-like habitat

6. T. rex ate Brachiosaurus
T. rex was over 70 million years later
T. rex did not live together with cavemen

7. Dinosaurs dragged their tail
probably held it upright as in T. rex

8. Dinosaurs were cold-blooded and sluggish
some were slow (ectothermic)
others were possibly warm-blooded (endothermic)

9. Dinosaurs were stupid
active predators are often cunning
evidence for nesting and mating behavior

10. Dinosaurs went extinct
   many did, but not birds
   birds are dinosaurs, reptiles, vertebrates
   conventional "dinosaurs" is paraphyletic because it excludes birds
   there are more living species of birds than mammals

The following outline of lecture notes does not follow Ch. 28 headings.

Also note, the text cladogram figures have some problems. Here are more details.

Click link to return to Lecture Schedule
or back to Chapter 27
or ahead to Chapter 30