Ask Me Everythingi

When did dinosaurs rule Earth?

Dinosaurs dominated our planet during the Mesozoic Era, 251 to 65 million years ago (mya), a time that we split into the Triassic, Jurassic, and Cretaceous periods. Great changes took place in the Mesozoic. Many new plant and animal groups appeared, but there were also mass extinctions.

How to: be Eoraptor, one of the first dinosaurs

Have long legs for running away from giant reptile predators.

Be smali (turkey-sized) for extra speediness.

DorYt have specialized teeth. Be versatile so that you can catch and eat just about anything.

! 03 ■ Walk	\ 04. Be
r upright rather than	warm-blooded.
on all-fours. You	_ You need to
t need your clawed	I be able to cope
J hands free to grab	r with both hot and
at animal prey.	1 cold ciimates.

Naming history

Mesozoic means “time of middle animals.” The creatures of this era came between those of the Paleozoic (545-251 mya) and the Cenozoic (65 mya to the present).

The Triassic Period

was named in 1834 for its three-fold rock sequence: black shales, chalk, and red sandstone.

The Jurassic Period

is named after the Jura Mountains in Switzerland, the place where the first Jurassic rocks were identified in 1795.

Creta is Latin for “chalk,” and the Cretaceous Period was when huge chalk cliffs were laid down (madę up of the fossilized remains of billions of tiny plankton).

12 animal groups that appeared in the Mesozoic

Stony corals

The corals that form coral reefs evolved in the Triassic from ancestors that resembled modern sea anemones.

Crabs

The first crabs appeared in the Jurassic. Crabs are crustaceans, closely related to lobsters but with a short, tucked-in taił.

Social insects

Wasps, bees, and ants appeared in the Jurassic or Cretaceous. The earliest were solitary, but group living evolved by 100 mya.

Teleost fishes

Most familiar bony fish are teleosts, which evolved in the Triassic. Examples include eels, herring, cod, carp, and salmon.

The earliest true frogs are from the Jurassic. Frogs are tail-less amphibians with short bodies and hind legs built for jumping.

Mammals

Warm-blooded, hairy mammals evolved during the Triassic. Mammals were successful in the Mesozoic, but mostly tiny.

(c) 2011 Dorling Kindersley. Ali Rights Reserved.