Dinosaurs  Lesson 3: Fossils
ACTIVITY: Two Legs or Four Legs
Objective
Students construct sets of two, four and five objects.
Materials
Dinosaur models of two and fourlegged dinosaurs
Sorting trays
Discussion
Tell students that all dinosaurs walked fully erect, unlike modern
reptiles like lizards and crocodiles that walk on their bellies with their legs
sprawling out from their sides. Dinosaurs are the only reptiles that walked like
mammals.
Some dinosaurs walked on two legs, some on four. All fourlegged dinosaurs were
herbivores. All carnivores were twolegged, although some herbivores were
twolegged as well.
Procedures
 Students sort the dinosaur models into those that have two legs and
those that have four legs. They count the legs and say that one plus one is the
same as two; two plus two is the same as four.
 Students draw pictures of the fourlegged dinosaurs and give reasons why these
would be herbivores (plant eaters).
 Students draw pictures of the twolegged dinosaurs and give reasons why these
would be carnivores (meat eaters).
 Students draw a set of three dinosaurs and say that three is one more than two,
or two more than one.
 Students draw a set of five dinosaurs and say that five is one more than four,
or four more than one, or three plus two.
