that ever existed. The name Eoraptor
means “dawn thief,” “early
plunderer,” or “dawn raptor.”
When and Where Eoraptor
Lived
Eoraptor lived about 231 to 223 million
years ago during the period of Earth’s
history called the Triassic. Eoraptor fossils,
or remains, have been discovered in
Argentina in South America. The dinosaur
lived on a lowland coastal plain
with many rivers and lakes.
Physical Features
Eoraptor was considerably smaller than
most of the later dinosaurs. It grew to an
average of about 3 feet (1 meter) in
length and weighed about 22 pounds
(10 kilograms). Eoraptor stood and
walked on its two back legs and had
short arms. It had hands with three long
clawed fingers at the end of each arm.
Eoraptor had different types of razorsharp
teeth. Its top teeth were jagged
like a saw and curved like those of other
meat-eating dinosaurs. The bottom
teeth were similar to those of the planteating
dinosaurs.
Eoraptor was not much larger than a modern-day chicken.
BRITANNICA STUDENT ENCYCLOPEDIA Eoraptor 145
Behavior
Eoraptor was a meat eater. It preyed on
small plant-eating dinosaurs. It also ate
mammal-like reptiles that were plentiful
at the time. Scientists believe that Eoraptor,
like other meat-eating dinosaurs,
also may have been a scavenger. This
means that it would have fed on dead
animals.
Epidemic
An epidemic is an outbreak of a disease
that quickly infects a large number of
people. When an epidemic spreads over
a wide area, it is called a pandemic. The
disease that causes an epidemic may be
passed from person to person. Or it may
be carried to people by something
nonhuman—for example, insects or
infected water.
There have been many deadly epidemics
throughout human history. In Europe
during the 1300s a disease called the
plague killed about 25 million people. It
became known as the Black Death.
Smaller outbreaks of plague struck European
cities for the next 300 years or so.
In 1918–19 there was a deadly influenza
(flu) pandemic. More than 20 million
people died throughout the world.
Epidemics are not as common as they
once were. Cleaner living conditions and
improved medicine have helped to slow
the spread of diseases. But epidemics of
diseases such as malaria and cholera still
happen in some parts of the world. The
disease called AIDS appeared in the
1980s and spread rapidly, especially in
Africa. In 2003 a flu-like illness called
SARS became an epidemic. SARS began
in Asia and spread throughout the world
within a few months.
#More to explore
AIDS • Disease, Human • Influenza
• Plague
Epilepsy
Epilepsy is a medical condition that
affects the brain. The brain’s cells communicate
with other cells by firing tiny
Women in Taiwan wear face masks to protect
themselves from getting an illness called
SARS. A SARS epidemic began in Asia in
2003.
A machine can check the electrical activity
of the brain to help determine if a person
has epilepsy.
146 Epidemic BRITANNICA STUDENT ENCYCLOPEDIA
electrical signals. An attack called a seizure
happens when brain cells signal
much faster than normal. People with
epilepsy suffer from such seizures.
Seizures range from mild to harsh.
Someone having a seizure may fall
down. Muscles may jerk, stiffen, or
become limp. The person may lose consciousness.
Breathing can stop temporarily.
The person may stare, blink, or
have sudden emotions.
Epilepsy may result from a brain injury
or a brain tumor. A stroke or a disease
that affects the brain can also cause epilepsy.
Sometimes epilepsy is passed
down from parent to child.
Epilepsy is hard to prevent. In about half
the cases the actual cause is not known.
People can lessen their chance of brain
injury by wearing seat belts in cars and
helmets on bikes.
There is no cure for epilepsy. Medicine
and a special diet can help control seizures.
Sometimes doctors perform brain
surgery. They may also place a small
machine under the person’s skin. The
machine sends electricity to the brain to
reduce the number of seizures.
#More to explore
Brain • Medicine
Equator
The equator is an imaginary circle
around Earth. It divides Earth into two
equal parts: the Northern Hemisphere
and the Southern Hemisphere. It runs
east and west halfway between the
North and South poles. The distance
around the equator is about 24,900
miles (40,000 kilometers).
The equator appears on maps and
globes. It is the starting point for the
measuring system called latitude. Latitude
is a system of imaginary east-west
lines, called parallels, that circle Earth
parallel to the equator. Parallels are used
to measure distances in degrees north or
south of the equator. The latitude of the
equator is zero degrees.
The equator passes through northern
South America, central Africa, the
Southeast Asian country of Indonesia,
and the islands of Oceania. These places
generally have warm climates. This is
because the equator receives more direct
sunlight throughout the year than any
other area of Earth.
#More to explore
Earth • Latitude and Longitude • Map
and Globe
An imaginary line called the equator runs
east and west around the middle of Earth. It
divides the globe into two parts, called hemispheres.
