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

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.

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

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.

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

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!

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…

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.

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

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