by Matt Wedel, UCMP

Calendar of dino events at LHS
LHS Big Dinos Return page


Archosaurs are a group of specialized reptiles which ruled the Earth during the Age of Dinosaurs. The only archosaurs that survive today are crocodiles and birds. Birds are the only group of dinosaurs that survived the extinction at the end of the Cretaceous period, 65 million years ago. Your holiday turkey is a saurischian dinosaur, like Apatosaurus, Tyrannosaurus, and Velociraptor.

Dinosaur cladogram

Saurischian and ornithischian hips

The ancestors of dinosaurs had a hipbone, the pubis, which pointed forward. The pubis evolved to point backward in two groups of dinosaurs: ornithischians and birds. Even though they share the same hip shape, many other features show that birds are actually saurischian dinosaurs. The evolution of a bird-like hip in ornithischians and birds is a case of convergent evolution, in which the same structure or shape evolves more than once.


Turkey skeleton

Features birds share with other archosaurs:

  • air-filled skull bones (all archosaurs)
  • legs carried under body (all ornithodirans)
  • neck with S-shaped curve (all dinosaurs)
  • air-filled bones in the neck and body (all saurischians)
  • wishbone (all theropods)
  • feathers (most theropods)
  • half-moon-shaped wrist bones (all raptors)

Features unique to birds:

  • keeled sternum for attachment of flight muscles
  • fused vertebrae in the back and tail
  • calf, instead of thigh, provides most of the power for walking and running


NOTE: Have an adult help you with these experiments.
Cleaning: Put the bones into a pot of water. Cover and boil the bones so that any remaining meat falls off (usually two hours at a light boil). Let the bones cool in the air for a few minutes or run them under cold water. Scrub the bones to remove all the remaining meat and cartilage.

Optional degreasing: Soak the bones overnight in soapy water to help degrease them.

Bleaching: Soak the bones for 24 hours in ordinary, drugstore-variety hydrogen peroxide.

Drying: Put a couple of paper towels on a plate, put the bones on the plate, and set them in the sun for a few hours.


• By chemically removing hard minerals from a T. rex bone, paleontologists recently found the soft tissue of T. rex blood vessels and cells. By exposing bones to vinegar or heat, you can see how bones change under experimental conditions. Find instructions online at Big Dinos Return (navigate to Experiments).

• Birds and other saurischian dinosaurs have many air-filled (pneumatic) bones. Discover similarities between birds and other dinosaurs by doing experiments that show the air spaces in bird bones. Find instructions online at Big Dinos Return (navigate to Experiments). Here are three CAT scan slices of an Apatosaurus neck vertebra. Compare the air spaces in Apatosaurus with those in your chicken or turkey bones.

Apatosaurus vertebrae cross-sections

• Dig up your dinosaur. Bury the bones of turkey or chicken in the backyard. Take a picture of the bones in the hole — it will serve as your quarry map later on. Mark the spot, and dig up the bones a few months later. Were you able to find all of the bones? Had any of them moved around? Clean the bones with soap and water, and you'll be ready to...

• Reconstruct your dinosaur (you can do this whether you buried the skeleton or not). A chicken or turkey from the grocery store doesn't come with a complete skeleton — the head and feet have already been cut off. That's okay — a lot of dinosaur skeletons are missing their heads and feet too. Pretend that you are a paleontologist reconstructing a new dinosaur. Without looking at the key, try to figure out which bones are which. Try drawing your interpretation of what the animal looked like. Then compare to the key to see how the skeleton really fits together.

• Build a model dinosaur skeleton out of chicken bones. Find out how in the books Make Your Own Dinosaur out of Chicken Bones and T. rex to Go, both by Chris McGowan.

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