Dinosaur Hip Groups
Classify dinosaurs into the two major groups based on hip structure: Saurischia (lizard-hipped, including theropods and sauropods) and Ornithischia (bird-hipped, including Triceratops and Stegosaurus)
What a learner can do afterwards
- Name the two major dinosaur groups: Saurischia and Ornithischia
- Explain the difference is based on hip bone structure (lizard-hipped vs bird-hipped)
- Correctly classify at least two dinosaurs into each group (e.g. T. rex = Saurischia, Triceratops = Ornithischia)
The lesson
Scientists sort every dinosaur into one of two big groups. The rule is not about size, and it is not about what the dinosaur ate. It is about the shape of the hip bones.
T. rex has hip bones shaped like a lizard's. Scientists call this group Saurischia, which means 'lizard-hipped.' Long-necked giants like Brachiosaurus belong to this same group too, even though they only ate plants. Hip shape matters more than diet.
Triceratops has different hip bones. One bone points backward, close to the shape you see in birds today. Scientists call this group Ornithischia, which means 'bird-hipped.' Stegosaurus belongs here too.
To sort a new dinosaur, check the hip bones, not the teeth or the size. A meat-eater and a plant-eater can land in the same hip group if their hips match.
Every dinosaur fits into one of two hip groups: lizard-hipped Saurischia (T. rex, Brachiosaurus) or bird-hipped Ornithischia (Triceratops, Stegosaurus).
Watch it
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Where this leads
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8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.