Page 76 - Ultimate Visual Dictionary (DK)

PREHISTORIC EAR TH

Tertiary period TERTIARY POSITIONS OF
PRESENT-DAY LANDMASSES

FOLLOWING THE DEMISE OF THE DINOSAURS at the end of the Cretaceous North Europe Asia
period, the Tertiary period (65–1.6 million years ago), which formed the first America
part of the Cenozoic era (65 million years ago–present), was characterized
by a huge expansion of mammal life. Placental mammals nourish and
maintain the young in the mother’s uterus; only a few groups of
placental mammals existed during Cretaceous times, compared
with a few dozen during the Tertiary period. One
of these included the first hominid (see pp.108–109),
Ardipithecus, which appeared in Africa. By the beginning of
the Tertiary period, the continents had almost reached their
present position. The Tethys Sea, which had separated the
northern continents from Africa and India, began to close up,
forming the Mediterranean Sea and allowing the migration of
terrestrial animals between Africa and western Europe. India’s South Australia
collision with Asia led to the formation of the Himalayas. America Africa
Antarctica
During the middle part of the Tertiary period, the forest-dwelling
and browsing mammals were replaced by mammals such as the horses,
better suited to grazing the open savannahs that began to dominate.
Repeated cool periods throughout the Tertiary period established the
Antarctic as an icy island continent.

EXAMPLES OF TERTIARY PLANT GROUPS

A PRESENT-DAY OAK A PRESENT-DAY BIRCH FOSSIL LEAF OF AN FOSSILIZED STEM OF
(Quercus palustris) (Betula grossa) EXTINCT BIRCH AN EXTINCT PALM
(Betulites sp.) (Palmoxylon sp.)

EXAMPLES OF TERTIARY
ANIMAL GROUPS

HYAENODON TITANOHYRAX PHORUSRHACOS SAMOTHERIUM
Group: Hyaenodontidae Group: Pliohyracidae Group: Phorusrhacidae Group: Giraffidae
Length: 6 ft 6 in (2 m) Length: 6 ft 6 in (2 m) Length: 5 ft (1.5 m) Length: 10 ft (3 m)

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