Page 203 - The Dinosaur Book and Other Wonders of the Prehistoric World (DK-Smithsonian)

Dromaeosaurs Mammoth
A group of birdlike, two-legged, A type of elephant with long Glossary
carnivorous dinosaurs. tusks that lived during the
Dromaeosaur fossils have been Pliocene and Pleistocene.
found on every continent. During the last ice age,
some mammoths developed
Embryo long hair, which helped
A plant, animal, or other them stay warm.
organism in an early stage
of development from an Marsupials
egg or a seed. A group of mammals in
Sinornithosaurus was a which offspring are born
Era birdlike dromaeosaur in an undeveloped state and
A very long span of time. Eras with feathers on its typically continue to grow
are divided into shorter spans arms and legs. inside a pouch on the mother.
called Periods. The Mesozoic
Era, for example, is divided Gravity Keratin Mesozoic
into the Triassic, Jurassic, The force of attraction that A tough structural protein The era of time that includes
and Cretaceous Periods. pulls objects to the ground. in hair, feathers, scales, the age of dinosaurs. It began
claws, and horns. 251 million years ago and
Evolution Hadrosaurs ended 66 million years ago.
The gradual change of species Also known as duck-billed Leaflet
over many generations as they dinosaurs. Large, bipedal A small, leaflike part of a Microbe
adapt to their changing and quadrupedal plant-eaters divided leaf. Short word for “microorganism.”
environment. from the Cretaceous Period.
They had a ducklike beak Lobed-finned fish Microorganism
Exoskeleton that was used for browsing A type of fish that has fleshy, Any living creature that is
An external skeleton. on vegetation. muscular fins. Lobe-finned too small to see without
Animals such as crabs fish were the ancestors of a microscope.
have an exoskeleton. In Herbivore all four-limbed vertebrates,
contrast, humans have An animal that eats plants. including humans. Monotremes
an internal skeleton. Egg-laying mammals, including
Ice age Mammal the platypus and the echidnas
Extinction A period of time during An animal that is (spiny anteaters). This
The dying out of a plant or which global temperatures warm-blooded, covered egg-laying habit is thought
animal species. Extinction can fall and sheets of ice (glaciers) in hair, and suckles to be the original mode of
happen naturally as a result of cover large areas of land. its young. reproduction for mammals.
competition between species,
changes in the environment, or Ichthyosaurs
natural disaster. A group of marine reptiles
that first appeared in the
Filaments Triassic Period. Ichthyosaurs
Thin, hairlike structures. had streamlined bodies similar
to present-day dolphins. They
Fossil became extinct before the end
The remains of something of the Cretaceous Period.
that was once alive, preserved
in rock. Teeth and bones are Iguanodontians
more likely to form fossils than Large, plant-eating dinosaurs
softer body parts, such as skin. that were common in the
early Cretaceous Period.
Fossilization
The process by which dead Invertebrates Lambeosaurus was a
organisms turn into fossils. Animals without backbones. plant-eating hadrosaur
that lived in western
Fossilization often involves North America about
replacement of the original Jawless fish 76 million years ago.
organism with rock minerals. A class of primitive
vertebrates that flourished
Frond mainly in Early Paleozoic
A leaf that is divided into times. They include extinct
many parts—for example, groups and the living hagfish
the leaf of a fern or a palm. and lampreys.

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