1. Reptiles, Mammals, and Birds
Reptiles, Birds, & Mammals
Amphibians
~400 MYA

2. Early Reptiles: Reptilomorphs
The earliest ancestors of reptiles are reptile-like amphibians.
Remember: what is THE defining characteristic of an amphibian?
The first “amphibian” that laid eggs on land… that’s our first reptile.

3. AMNIOTES: Reptiles, Mammals and Birds
An amnion is the membrane “sac” in which an embryo develops.
Labeled 2
Both egg-laying and live-birthing animals may have an amnion

4. Reptiles: What is a Reptile?
Includes lizards, snakes, crocodiles, turtles, and similar species.
Aerobic, ectothermic amniotes with scales.
The Komodo dragon (pictured) is the largest living reptile – it can grow to over 10 feet.

5. Oviparous Animals Lay Eggs
For land-dwellers, fertilization is internal.
Almost all embryonic development happens inside the egg.

6. Dinosaurs: Famous Reptiles
The group of reptiles from which all true dinosaurs evolved includes crocodiles as well as ostriches…
Appear around 250 MYA, during the Triassic period of the Mesozoic Eon… and some survive today!

7. More about mammals tomorrow…
Mammal-like Reptiles
Cynognathus (shown) is an example of one of several fossil species that show divergence from the reptile line.
The first true mammals (with mammary glands, fur, etc.) arise in the Triassic, about 200 MYA.
More about mammals tomorrow…

8. Class Aves: For The Birds
Birds are close relatives to the dinosaurs
This bird is preening – a feather cleaning activity that keeps them working just right.

9. Birds = Surviving Therapod Dinosaurs
Wishbone
Hollow bone structure
3-toed foot
Oviparous and brooding (nesting)

10. What’s a Bird? Wings, two legs Endothermic Oviparous
Modern birds all have:
Feathers
Toothless beak
Hard-shelled eggs
4 chambered heart
Hard endoskeleton