Dinosaurs lived between 220 and 65 million years ago.
Although the age of dinosaurs is the Mesosoic Era,
(which is divided into three periods - Triassic, Jurassic and
Cretaceous), dinosaurs actually first evolved towards the end of
Triassic. Dinosaurs evolved from the ancient archosaurs,
so the first dinosaurs were like archosaurs.
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From there they evolved
into two groups - saurischia, and (later) ornithischia. The difference
between the two were their hip bones - saurischias
were "lizard-hipped", and ornithischias
were
"bird-hipped".
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Saurischias evolved into two groups: Sauropodomorpha and
Theropoda.
Theropods were carnivorous dinosaurs, they were quick
runners and moved on two feet. Their front feet were small, a bit like
these of kangaroos. Theropods developed futher to Herrerasaurs,
Coelophysosaurs, neocreatosaurs (which later developed to abelisaurs),
and Tetanurae - a group that further developed to coelurosaurs,
carnosaurs, spinosaurs, allosaurs, Compsognathidae, Therizinosaurs,
Troodontidae, Ornithomimosaurs, oviraptorosaurs, alvarezsaurs,
deinonychosaurs, and Tyrannosaurs. They were all meat eaters except
Therizinosaurs, which returned to eating plants.
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Sauropodomorpha were long-necked plant
eaters with
lizard-like
feet. They further evolved into two different groups: Prosauropods
(massospondylidae, plateosauridae, melanorosauridae and ancisauridae);
and sauropods
- the largest animals that have ever excisted. They were massive
long-necked elephantine plant-eaters which, due to their weight, walked
on four legs. They included cetiosaurs, dicraeosaurs, Euheloptidae,
Diplodocidae, Vulcanodontidae, and Macronaria (which later developed
into titanosaurs).
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Ornithischia, the second large group that
dinosaurs evolved to, were bird-hipped plant eaters. They evolved into
five groups: Ornithopoda, Fabrosauridae, Heterodontosauridae,
Thyreophora and Marginocephalia. Ornithopoda
were bird-footed plant eaters that evolved to Hypsilophontidae, and
Iguanodontidae which further evolved to hadrosaurs, lambeosaurs, and
hadrosaurs (Edmontosaurini, Maiasaurini, Saurolophini, and
hadrosaurini). Thyreophora
were armoured dinosaurs, which evolved to spectacular stegosaurs (with
plated back), and Ankylosauria, which further evolved into Nodosauridae
and Ankylosauridae (Polaxanthidae and Ankylosaurinae). Marginocephalia
were also armoured, but with horns on their heads instead of spikes or
plated on their backs. They evolved into two groups: Patchycephalosaurs
(boneheads) and Ceratopsia (hornheads), which further evolved into
neoceratopsia, ceratopsidae, centrosaurinae, ceratopsinae and
chasmosaurini. That's the main lines in dinosaur history.
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