---
title: "Dinosaur Hip Groups"
description: "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)"
canonical: https://lightmysky.com/learn/science/dinosaur-hip-groups-mt_yrSdVrXrsF
source: https://lightmysky.com/learn/science/dinosaur-hip-groups-mt_yrSdVrXrsF.md
retrieved: 2026-10-19
---

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# 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)

Subject: Science · Area: Dinosaurs & Paleontology · Ages 9 to 11
Page: https://lightmysky.com/learn/science/dinosaur-hip-groups-mt_yrSdVrXrsF

## Ready when they can

- 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)

## Lesson: Lizard Hips and Bird Hips

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.

**Example.** 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.

**Example.** 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.

*(drawing: Four dinosaurs from this lesson, sorted by hip shape: two with lizard hips and two with bird hips.)*

**Tip.** 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.

**Recap.** Every dinosaur fits into one of two hip groups: lizard-hipped Saurischia (T. rex, Brachiosaurus) or bird-hipped Ornithischia (Triceratops, Stegosaurus).

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Famous Dinosaur Species](https://lightmysky.com/learn/science/famous-dinosaur-species-mt_BnabTHkNIp)
- [Plant-Eaters vs Meat-Eaters](https://lightmysky.com/learn/science/plant-eaters-vs-meat-eaters-mt_DJh2JPwTf6)

## Opens up

- [Reading Cladograms](https://lightmysky.com/learn/science/reading-cladograms-mt_cSPtyLF3q1)
- [Birds Evolved from Dinosaurs](https://lightmysky.com/learn/science/birds-evolved-from-dinosaurs-mt_T8JGTJ-oNI)