The success of the dinosaurs is exemplified by their extensive range.They
occupied a wide variety of habitats and dominated all other forms of land-
dwelling animals. Indeed, had the dinosaurs not become extinct, mammals
would never have achieved dominance over Earth and humans would not have
come into existence.This is because the dinosaurs would have continued to sup-
press further advancement of the mammals, which would have remained small,
nocturnal creatures,keeping out from underfoot of the dinosaurs.
Dinosaurs are classified as either sauropods or carnosaurs. Sauropods
were long-necked herbivores. Carnosaurs were bipedal carnivores that possi-
bly hunted sauropods in packs. Camptosaur (Fig. 135), ancestor of many later
dinosaur species, was a herbivore up to 25 feet long. Not all dinosaurs were
gigantic, however. Many were about the size of most modern mammals.Pro-
toceratops and ankylosaurs were no larger than the biggest terrestrial mammals
TRIASSIC DINOSAURSTABLE 8 Continental DriftGeologic Division
(millions of years) Gondwana Laurasia
Quaternary 3 Opening of the Gulf of California
Begin spreading near
Pliocene 11 Galapagos Islands Change spreading directions in eastern
Opening of the Gulf of Aden PacificMiocene (^26) Opening of the Red Sea Birth of Iceland
Oligocene 37 Collision of India with Eurasia Begin spreading in the Arctic Basin
Eocene (^54) Separation of Australia Separation of Greenland from Norway
Paleocene 65 from Antarctica
Separation of New Zealand Opening of the Labrador Sea
from Antarctica Opening of the Bay of Biscay
Separation of Africa
from Madagascar and Major rifting of North America
South America from Eurasia
Cretaceous 135 Separation of Africa from India,
Australia,New Zealand,
and Antarctica
Jurassic 180
Begin separation of North America
from Africa
Triassic 250