T

his chapter examines the creatures that took flight and covers the largest
animals ever to inhabit Earth during the Jurassic period. The Jurassic,
from 210 to 135 million years ago, was named for the limestones and
chalks of the Jura Mountains in northwest Switzerland. Early in the period,
Pangaea began rifting apart into the present-day continents, forming the
Atlantic, Indian, and Arctic Oceans. Mountains created by crustal upheavals dur-
ing previous periods were leveled by erosion. Inland seas invaded the conti-
nents,providing additional offshore habitats for a bewildering assortment of
marine species (Fig. 144). By this time, terrestrial faunas had attained the basic
composition they would keep until the dinosaurs became extinct.
The dinosaurs were highly diversified during the Jurassic and reached
their maximum size, becoming the largest terrestrial animals ever to live.
Widespread plant growth and coal formation suggest a warm, moist climate.
The beneficial climate and magnificent growing conditions contributed to
the giant size of some dinosaur species, many of which became extinct at the
end of the period. Reptiles were extremely successful and occupied land, sea,
and air. Mammals were small, rodentlike creatures, sparsely populated and

11

JURASSIC BIRDS

THE AGE OF FLYING CREATURES