Page 27 - Reptiles & Dinosaurs (Britannica Illustrated Science Library)

22 DINOSAURS REPTILES AND DINOSAURS 23

The Cretaceous Period CRETACEOUS 140 TO 65

The name is based on the Latin word An Evolving Planet
creta, which means stone. The name During this period of 80 million years, levels rose, currents increased ocean MILLION YEARS AGO
as an age of expansion. The dinosaurs continued to diversify, comes from the layer of limestone the Earth's climate changed. Its temperatures, and marine fauna multiplied. The Earth began to adopt an appearance
and the first snakes appeared. The Earth began to look like the found in the rock formations that temperate climate, accompanied by snow in On land, the first flowering plants similar to that of today. Africa and South
define this geological system.
(gymnosperms) appeared, and forests of
the polar regions during the winter, was
America separated from one another, as did
W planet we know today. The movement of tectonic plates transformed into a warm, mild climate with willow, maple, and oak harbored the last North America and Europe. The North and
created folds that came to form some of the mountain ranges of noticeably different seasons. The ocean large dinosaurs. South American plates drifted westward
and collided with the Pacific plate, raising
today, such as the Appalachians in North America and the both the Rocky Mountains in North
Alps in Europe. At the end of this period, another mass ALPINE MOUNTAIN-BUILDING America and the Andes in South America.
During this period, Africa and
extinction event occurred, Eurasia drifted closer together.
probably caused by the The Tethys Sea narrowed, and
the collision of plates formed the
impact of a meteorite. Alpine mountain range.
NORTH EURASIA
AMERICA
INDIA
ÁFRICA
SOUTH
AMERICA

FORESTS ANTARCTICA
Oaks and maples
predominated in the
most humid regions.

FLYING REPTILES
developed very large wingspans
toward the end of this period.

Flora

During the early Cretaceous
Period, ferns and conifers MARINE REPTILES
predominated. Important groups became The expanding seas
extinct at the boundary between the Early and caused an abundance of
Late Cretaceous. These species were replaced marine reptiles and
in tropical forest environments by flowering other aquatic species,
plants, which spread to colder and drier areas.
such as mollusks.

FLOWERS Fauna
During this period, the
main advancement in the
evolution of plants was The Cretaceous Period held the greatest
the appearance of diversity of dinosaurs. This epoch is also
angiosperms, or plants known for small mammals, insects, and the
with flowers and fruit. largest flying reptiles.