Stones & Bones: Leapin' Lizards—Alligator Aerobics

Scientists now think dinosaurs were active, warm-blooded animals. To be able to escape from predators or to chase food, dinosaurs must have been able to run and breathe at the same time. Lizards, which are cold-blooded, use the same muscles for running and breathing; so they have to run, then stop and breathe, then run again. So how did the dinosaurs do it?

Researchers at the University of Utah may have found the answer by looking at alligators, which share a common ancestor with dinosaurs. They had small gators, up to three feet long, run on a treadmill. The gators wore masks so the scientists could measure how much oxygen they consumed and how deeply they inhaled, as well as monitors to determine what muscles they used. To their surprise, the researchers found that part of the alligator's pelvis or hip bone was hinged and moved when the critters ran. In gators, it turns out, the hip bone links to the liver, which links to the lungs. When they run, the movement of the hip bone first pulls on the liver, which pulls on lungs, helping inflate them; then it goes the other way, pushing the liver into the lungs, forcing the air out of them. The researchers think that dinosaur hip bones may have worked in a similar fashion.


  1. What is the relationship between an alligator and a dinosaur?
    [anno: Scientists believe that alligators have a common ancestor with dinosaurs.]
  2. In Lesson 1, you learned about the different periods in the Geologic Time Scale. Bacteria, fungi, and algae all developed during the Precambrian period. How long ago did these organisms first appear?
    [anno: Bacteria appeared 3.5 billion years ago. Fungi and algae appeared one billion years ago.]
  3. The dinosaurs lived during which period?
    [anno: Mesozoic]
  4. Why do you think that the dinosaurs became extinct around 65 million years ago but that algae, fungi, and algae and bacteria are still present on the planet today? Write a few sentences explaining your answer.
    [anno: Answers will vary but could include the fact that bacteria, fungi, and algae are fairly simple life forms and can probably evolve more easily than the dinosaurs did.]