the group of dinosaurs known as theropods.
The theropods were meat-eating
dinosaurs that walked on their two back
legs.
When and Where Allosaurus
Lived
Allosaurus lived about 163 to 144 million
years ago. Most Allosaurus fossils, or
remains, have been found in North
America, in Colorado, Utah, New
Mexico, Montana, South Dakota, and
Wyoming.
Physical Features
Allosaurus reached up to 39 feet (12
meters) in length, stood about 15 feet
(4.5 meters) tall, and weighed up to 2
tons. The massive head of Allosaurus
measured about 3 feet (1 meter) long
and was supported by a short, thick
neck. The sharp teeth of Allosaurus were
curved and had sawlike edges. Allosaurus
had sharp claws on the three toes of each
hind foot. It also had long, grasping
claws on the three toes of each front foot.
The long, heavy tail of Allosaurus may
have helped the animal balance itself.
Behavior
Allosaurus was a meat-eating dinosaur
that preyed on plant-eating dinosaurs.
When it hunted alone, Allosaurus would
hide among thick plants and then jump
out on its prey. Some scientists believe
that Allosaurus also hunted in packs.
Together, a pack of Allosaurus could
bring down very large dinosaurs, such as
Apatosaurus and Diplodocus. Scientists
believe that Allosaurus reproduced by
laying eggs.
#More to explore
Dinosaur Tyrannosaurus rex
Allosaurus
86 Allosaurus BRITANNICA STUDENT ENCYCLOPEDIA
Alloy
An alloy is a substance made of two or
more metals or of a metal and nonmetallic
materials. To make an alloy, the
ingredients are melted and mixed
together. When the mixture cools, it
hardens.
Alloys are generally more useful than
pure metals. Pure metals may rust or
wear away easily. They may also be too
soft to hold a shape. But mixing other
substances with a pure metal often
results in a hard and strong substance.
People first learned to make alloys more
than 5,000 years ago. Ancient peoples
used a combination of copper and tin,
called bronze, to make tools and weapons.
Today such things as church bells
and statues are made of bronze. Brass, a
combination of copper and zinc, is
another ancient alloy. People today use
brass to make such things as doorknobs
and musical instruments.
Steel is one of the most important modern
alloys. Steel is a mixture of iron,
carbon, and other substances. Steel is
useful in building construction and
many other industries. Another important
modern alloy contains aluminum
and small amounts of copper or other
substances. Aircraft and other vehicles
are often made of aluminum alloys.
#More to explore
Brass Bronze Metals Steel
Almond
Almonds are commonly called nuts, but
they are actually seeds. They come from
a tree that is closely related to the peach
tree. People eat almonds as a snack and
also use them in cooking and baking.
Almonds can also be pressed to obtain a
fragrant oil.
The United States, Spain, Greece, Iran,
and Turkey are major almond producers.
Most almonds produced in the United
States come from California.
There are two types of almonds: sweet
and bitter. Sweet almonds are the kind
people eat. Bitter almonds contain a
poison, but their oil can be used for
food after the poison is removed.
Almond trees do not grow much taller
than 30 feet (9 meters). They bloom in
early spring. Bitter almond blossoms are
white, and sweet almond blossoms are
pink. The fruits look like peaches, but
they are smaller and flatter. Inside each
fruit is a pit, or nut. The nut has a hard
A South American mask is made of a gold
and silver alloy. Its ears and eyes are made
of copper.
Stainless steel
is an alloy that
contains iron,
chromium,
and other metals.
Stainless
steel is useful
because it
does not rust
easily.
BRITANNICA STUDENT ENCYCLOPEDIA Almond 87
shell surrounding a seed. The seed is the
part that people eat.
As the fruit ripens, it splits open to
reveal the nut.Workers use machines to
shake the trees and make the nuts fall to
the ground. The nuts may be left to dry
on the ground, or they may be dried in
an oven.Workers then use machines to
shell, sort, and pack the nuts for shipment.
#More to explore
Nuts Peach
Alphabet
An alphabet is a system used to represent
language in written form. Each letter
stands for a single spoken sound. Many
languages use alphabets. But some languages
use other systems to represent
words in writing. For instance, in Japanese
and Cherokee each symbol represents
a group of sounds rather than a
single sound. The Chinese writing system
uses symbols to represent the meaning
of words, not their sounds.
The Latin alphabet is the alphabet of
English and most European languages.
It has 26 letters. Other alphabets might
have fewer or more letters. Like other
alphabets, the Latin alphabet developed
from earlier forms.
EarlyWriting Systems
People in early societies drew pictures to
communicate ideas. In ancient times
people in the Middle East developed the
worlds first writing system. It used symbols
to stand for the meanings of words.
Later it also used some symbols to represent
the sounds of words.
More than 3,000 years ago people in
what is now Syria used a simpler writing
system. This system is called North
Semitic. Most modern alphabets trace
their history back to that system. North
Semitic used only 22 symbols. It did not
have any signs representing whole
words. Instead each letter represented a
consonant. There were no symbols for
vowels. People known as the Phoenicians
later slightly changed this system.
The fruits of the almond tree open to reveal
the nuts. The almond seeds are inside the
hard shells.
A computer keyboard has Latin and
Japanese letters. It sits on top of a document
written in Chinese characters.
88 Alphabet BRITANNICA STUDENT ENCYCLOPEDIA
Greek and Latin Alphabets
The ancient Greeks changed the Phoenician
writing system to create their own
alphabet. Some people consider the
Greek alphabet to be the first true alphabet.
This is because it has symbols for
vowels and consonants. The Greek
alphabet is the ancestor of all modern
European alphabets, including Latin.
The ancient Romans, who spoke Latin,
developed the Latin alphabet. As the
Roman Empire grew, the Latin alphabet
spread throughout the empires vast
lands. It became the alphabet of many
other languages in addition to Latin.
The alphabet changed over time. New
letters were needed to pronounce words
in other languages. Other letters were
combined.
Other Alphabets
The North Semitic writing system also
gave rise to other ancient alphabets,
including Aramaic. The modern Hebrew
and Arabic alphabets developed from the
Aramaic alphabet. Today people in Israel
and Jews around the world use the
Hebrew alphabet. People in large parts of
theMiddle East and North Africa use
the Arabic alphabet. In Hebrew and
Arabic a small group of consonants gives
the basic meaning of a word. Vowels
slightly change the meaning.
The ancient Aramaic alphabet probably
also influenced the earliest-known writing
system of India. This system, called