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🦕 The Two Dinosaur Families

Every dinosaur belongs to one of two great families, and the secret is in the hips. Meet the lizard-hipped and bird-hipped dinosaurs.

lessons

~15 min

to learn

🔬 Science

subject

Ages 6–12

level

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What you’ll learn

It's All in the HipsIdentify the three hip bones and explain how the direction of the pubis divides dinosaurs into two families.Scientists split all dinosaurs into two families using the hip. The hip has three bones: the ilium on top, the pubis at the front, and the ischium at the back. If the pubis points forward, the dinosaur is a lizard-hipped saurischian; if it points backward, it is a bird-hipped ornithischian.
SaurischiansDescribe the saurischians as the theropods and sauropods, and explain that birds evolved from them.Saurischians, the lizard-hipped family, include the meat-eating theropods like T. rex and the long-necked sauropods like Brachiosaurus. Surprisingly, real birds evolved from theropods, so birds are lizard-hipped — even though the other family is nicknamed 'bird-hipped'.
OrnithischiansDescribe ornithischians as mostly plant-eaters and correctly sort famous dinosaurs into the two families.Ornithischians, the bird-hipped family, were almost all plant-eaters, including Triceratops, Stegosaurus, and the duck-billed hadrosaurs. Despite the 'bird-hipped' nickname, they are not the ancestors of birds. Knowing the hip rule lets you sort any dinosaur into its family.

Questions this course answers

What body part do scientists use to split dinosaurs into two families?

Dinosaurs are divided into two families based on the shape of their hips.

Which hip bone's direction decides a dinosaur's family?

The pubis is the front hip bone, and which way it points decides the family.

In a 'lizard-hipped' saurischian, which way does the pubis point?

In saurischians (lizard-hipped), the pubis points forward.

Which two groups make up the lizard-hipped saurischians?

Saurischians include the meat-eating theropods and the long-necked sauropods.

Which family did real birds actually evolve from?

Even though ornithischians are nicknamed 'bird-hipped', real birds evolved from saurischian theropods.

Which dinosaur is a bird-hipped ornithischian?

Triceratops is a plant-eating, bird-hipped ornithischian. The others are lizard-hipped saurischians.

Grounded in trusted sources

Natural History Museum
American Museum of Natural History
Smithsonian's National Museum of Natural History
Britannica Kids

Every Wunder lesson is built from real, reputable sources — never invented.

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