Grade Level: K-2

Purpose: Students will compare two kinds of dinosaurs based upon the structure of the pelvis: bird-hipped and reptile-hipped

Skills: communicating, comparing, classifying

— Clear communication is an important part of science
— Living things can be sorted into groups by features
— Different features allow animals to adapt different lifestyles

Background: Morris was an Apatosaurus. Scientists classify dinosaurs into two major groups: those with reptile-like hips and those with bird-like hips.


— Dinosaur classification chart
— Art supplies
— Dinosaur journal sheet
— Models of dinosaurs.


There are three bones in the hip area: ilium, ischium, and pubis. The following finger play will help students visualize the arrangement of these bones.

Hold your hand as shown in the diagram. The top of the hand represents the broad hip bone at the top side of the pelvis (ilium). The index finger represents the bone in the front (pubis), while the thumb represents the back hip bone (ischium). Hold both hands together, back to back, so that the index fingers and thumbs are touching. This forms the pelvic girdle. The reptile-hipped dinosaurs are represented with the thumb and index finger (ischium and pubis) pointing in the opposite directions.
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The bird-hipped dinosaurs are represented with the index finger (pubis) pointing in the same direction as the thumb (ischium), which is toward the tail.

After the students have modeled both kinds of dinosaurs with their hands, have them locate both kinds of dinosaurs on the classification chart. Have them show you with their hands whether the following are reptile-hipped or bird-hipped: Apatosaurus, Hadrosaurus, T. rex, and Triceratops. To make it easy, all of the meat eaters and the sauropods (long necks) were reptile-hipped. The rest of the plant eaters were bird-hipped.

Set dinosaur models on the tables. Let the students use them to draw a reptile-hipped and a bird hipped dinosaur on their activity sheets.

Draw a bird-hipped dinosaur and a reptile-hipped dinosaur.

Tell why each fits in that group.