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!
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