Page 18 - DINOSOUR ATLAS

dinosaur atlas
What is a Dinosaur?

The dinosaurs evolved from
reptiles called the archosaurs, MYa archosaurs
which were also the ancestors of . 220
modern crocodiles. But unlike the
sprawling crocodiles, dinosaurs
walked on upright legs, which . 210

is more efficient. Some were
probably warm-blooded, with
insulating feathers. They all . 200

lived on land and laid eggs.

. 190

. 180

saurischian pelvis . 170

. 160

ornithischian pelvis
. 150
u dinosaur hips fabrosaurids and heterodontosaurids
There were two main types of dinosaur. . 140
Giant sauropods like Diplodocus and
ferocious theropods like Tyrannosaurus were
“lizard-hipped” saurischians, with a large
bone called the pubis pointing down between . 130
the hind legs. Other dinosaurs like Iguanodon
were “bird-hipped” ornithischians, with a
smaller pubis. Confusingly, modern birds
actually evolved from saurischian dinosaurs. . 120

. 110

. 100
u pterosaur
The pterosaurs were not . 90 ankylosaurids pachycephalosaurs iguanodontids hypsilophodontids
dinosaurs, but they had the nodosaurids stegosaurids ceratopsians psittacosaurs hadrosaurids
same archosaur ancestors. They had a lot
in common with the dinosaurs, but were not . 80
related to the group that eventually gave
rise to the birds.
. 70
ankylosaurs ceratopsians ornithopods
ornithischia (bird-hipped)

u iChthYosaur
The dolphinlike ichthyosaurs and other
marine reptiles were part of a group called the
euryapsids. These evolved separately from
the archosaurs, but lived at the same time.
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