BACKGROUND:
Paleontologists rely on several different types of fossil clues to
interpret the eating habits of extinct animals, including dinosaurs. Teeth
are the best clues to determine what dinosaurs ate. Dinosaurs with sharp,
pointed, serrated teeth throughout their mouths, like Tyrannosaurus, Allosaurus
,or Coelophysis, ate meat. Their teeth acted like built-in steak
knives for slicing soft flesh. The plant-eating dinosaurs had flatter, wider
teeth for grinding up tough plant material. The duckbilled dinosaurs (the
hadrosaurs) were one type of plant-eating dinosaur. Some of these had
thousands of teeth in their mouths for grinding vegetation. Even with many
teeth, some of the herbivore dinosaurs weren't able to grind plant material
well enough in their mouths to be able to digest it. Some of them swallowed
stones, called gastroliths, that stayed in their digestive tract to
help pulverize food after it was swallowed. There were also omnivorous (both
plant- and meat-eating) dinosaurs that had teeth that were intermediate in
shape, between those of the carnivores and those of the herbivores.
Dinosaur posture is also a clue to food type. All of the carnivorous
dinosaurs were bipedal (walked on two legs), while all of the herbivorous
dinosaurs were either quadrupedal (walked on four legs) or spent some time
on two and some time on four legs. Physical characteristics are also clues
to dinosaur eating habits. Carnivores had large, sharp claws. Herbivores
commonly had armatures such as horns, bony skull frills, plates, thickened
bones, or tail/thumb spikes for protection. Carnivores had little or no
armature, probably because it would have slowed them down in their pursuit
of prey.
This lab reviews the difference between carnivores and herbivores.
Students will learn to tell the differences between them by recognizing key
physical traits.
PROCEDURE:
- Explain to the class that we can make very good guesses about what
different dinosaurs ate by looking at the shapes of their teeth and
bodies. Dinosaurs with sharp, pointed teeth that walked on two legs were
carnivores (meat-eaters); dinosaurs with flatter, grinding teeth that
walked on four legs (all or part of the time) were plant-eaters.
- Play "grind and chew" with the class. Have the class stand
in a circle. An animal that eats plants has both vertical and lateral
motion in the lower jaw. Make a motion with your jaws to illustrate the
cow-like, sideways, grinding motion of a herbivore. Carnivores
"bite" with an upward and downward (mainly vertical) motion,
like a lion. Demonstrate the difference in this second type of motion to
the class. Have students join you practicing carnivore and herbivore
eating motions. Because humans eat both plants and meat, our jaw motion
allows for both grinding and chewing.
- Hand out the worksheet and have students color dinosaurs with
herbivore-like teeth green and those with carnivore-like teeth red.
(Skulls 1 and 4 are carnivores; skulls 2 and 3 are herbivores.)
- Display the Carnegie dinosaur models and other dinosaur models. Ask
the class to identify carnivores and herbivores. If you want to extend
the lab, use the dinosaurs in the extinct animal models. The Dinosaur
Placemats can also be used. The eating habits of the Carnegie Model
dinosaurs are given below
