DINOSAUR GROUPS
All
known dinosaurs are divided into two large groups: Saurischia ("lizard-hipped") and Ornithischia ("bird-hipped"). Most
saurischians had forward-jutting pubic hip bones, while in
ornithischians each pubic bone slanted back, parallel to the
ischium.
There were two major saurischian subgroup: the
carnivorous, bipedal theropods and the plant-eating, mostly
quadrupedal sauropodomorphs.
Ornithischians (all
plant-eaters) were divided into three main groups: birdlike
ornithopods, armored thyreophorans, and horned or thick-skulled
marginocephalians.
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