dinosaur behavior - the Scientia Review

DINOSAUR BEHAVIOR
Leighton Moylan and Olivia Silva
1
Table of Contents
Introduction
Classification
Herbivores
Omnivores
Carnivores
Extinction
Birds
Glossary
Image Credits
About the Authors
2
4
5
7
9
11
12
13
17
18
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Introduction
The term dinosaur refers to a group of extinct animals that
lived 230 million years ago that belonged to the reptilian kingdom.
Dinosaurs thrived during the Triassic, Jurassic, and Cretaceous
periods, which spanned 164 million years. Dinosaurs were the
dominant terrestrial animals during the prehistoric era. These
animals are separated into three
main
groups:
herbivores,
carnivores, and omnivores,
which
are
based
dinosaurs’ diets.
on
the
Herbivores
only ate plants, carnivores only
ate meat, and omnivores ate
both plants and meat.
Scientists
who
study
prehistoric animals, such as
Small dinosaur fossils
dinosaurs, are known as paleontologists.
The only information paleontologists can find about dinosaurs come
from their fossils, which are preserved
Did you know?
The
Chinese
dinosaur
dinosaur skeletons and traces (such as
thought
fossils
were
dragon bones and used
them to make medicine.
The
first
dinosaur
recognized
fossils
found in England.
were
footprints and feces).
3
Introduction
Scientists can hypothesize about dinosaur behaviors just by
observing the fossils.
There are
certain physical traits that reflect
certain behaviors.
For example,
carnivores need sharp teeth to be
able to tear meat.
By analyzing
fossils, scientists are also able to
estimate the time that the dinosaurs
existed.
Paleontologists
discovered
over
1,000
have
different
species of dinosaurs. Fossils must be
The basic tools used by paleontologists
carefully cleaned and dug up using special tools such as
paintbrushes and dental picks. This process is very tedious because
the fossil itself must remain unharmed while the soil must be
completely removed.
Dinosaur footprints
4
Classification
Dinosaurs belong to the kingdom Animalia, phylum Chordata,
and class Reptilia.
As with other reptiles, all dinosaurs lay
amniotic eggs, which means they do not require water to survive.
Most species made elaborate nests for their eggs.
One species,
Maiasaura, lived in packs and nested in colonies. There were only
seven meters between each nest, and each nest contained 30 to 40
eggs. The mother did not sit on her young to keep them warm;
instead, she inserted rotting plants in the nest, which would emit
heat.
Although paleontologists do not have evidence, they speculate
that dinosaurs had similar
skin to modern reptiles,
which have impermeable
scales.
Dinosaurs share
multiple
traits
common
reptiles,
allows
scientists
with
which
to
hypothesize that dinosaurs
A reconstructed Maiasaura nest with eggs
had
an
epidermis
that
resembled that of reptiles.
Scientists do not know much about the physiology of soft
tissues in dinosaurs because there are not many fossils containing or
depicting organs.
5
Herbivores
Paleontologists have discovered numerous herbivore dinosaur
fossils.
because
They are easily identifiable
of
their
distinguishing
physiological features. Herbivorous
dinosaurs had teeth for consuming
plants, which were much different
from those of carnivorous dinosaurs.
The
most
herbivorous
well
dinosaurs
known
are
the
The Brachiosaurus, a type of Sauropod
Sauropods. They are noted for their elongated necks, small heads,
and long front legs. These
animals also had long tails,
which scientists speculate
were for rearing up on their
hind legs. The tail balanced
the dinosaur and acted like
a tripod.
t
e
Sauropods had
Examples of gastroliths
eth that were blunt, narrow, and well spaced. They were used to
rake leaves off trees and vegetation off the ground.
These dinosaurs could not chew their food; they swallowed
rocks known as gastroliths to churn the vegetation and aid in
digestion. Paleontologists often found gastroliths in the abdomens
of fossilized dinosaurs and considered this digestive behavior
specific to herbivorous dinosaurs.
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Herbivores
The other main category of herbivores was the Ornithopods.
Unlike Sauropods, these dinosaurs were able to chew their food;
therefore, swallowing gastroliths was unnecessary.
Their jaws
resembled a beak of a bird and had hind teeth that were for chewing
vegetation.
Their teeth were grouped into sections and were
serrated, similar to a cheese grater. As old teeth wore out, new teeth
replaced them.
These dinosaurs thrived on plants low to the ground, as
evidenced by their small necks and short height. These dinosaurs
were
originally
bipedal
organisms, but
they
eventually
into
larger
animals.
small
evolved
quadrupedal
The
earliest
Ornithopods were only one
A bipedal Ornithopod
meter long, where the later
dinosaurs were 15 meters long. Ornithopods were able to run,
despite
their
large
bodies.
Running was one of their few
defense mechanisms; they did
not have sharp teeth or claws.
The smaller Ornithopods were
the fastest dinosaurs.
A drawing of a quadrupedal Ornithopod
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Omnivores
There were also omnivorous dinosaurs, or those that ate both
plants and meat. Some carnivorous dinosaurs were found with
plants in their intestines, but most of these instances appear to be
coincidental. However, paleontologists have evidence that there
were dinosaurs that consumed both plants and animals on a regular
basis. Omnivores often had physiological survival advantages that
allowed
them
to
rely
on
numerous food sources. Most
of
these
medium
dinosaurs
sized
were
because
accessing all both plants and
animals was necessary for
their survival.
Omnivorous
dinosaurs
were physiologically capable
An illustration of Heterodontasaurus
of consuming a variety of
foods. One specific dinosaur,
Heterodontasaurus, had teeth that were specifically for eating both
plants and animals. It had pointed canine teeth similar to those of
carnivores such as T. rex and more robust back teeth that were for
grinding vegetation.
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Omnivores
Ornithomimus was a large dinosaur at four meters long and
could run at high speeds similar to a modern ostrich. It also had a
large beak-like mouth that lacked teeth. This mouth structure would
not be suitable for eating meat. Instead, scientists speculate that this
dinosaur survived on a diet that was mostly plants with some small
animals. Ornithomimus could reach high speeds and had a beak,
which are characteristics of carnivores and herbivores, respectively.
Scientists originally thought that omnivores, such as Oviraptor,
preyed upon other dinosaurs’ eggs. This came from a discovery of
an Oviraptor fossil in a presumably predatory position over a nest
of eggs. However, scientists
later found that the eggs
were Oviraptor offspring
and
realized
that
the
dinosaur was protecting its
eggs. Its mouth structure
reinforced the notion that
Oviraptor did not eat eggs.
The jaw had no teeth, but it
did have strong muscles.
This structure would not
be efficient for cracking
The Oviraptor, which was not an egg hunter, contrary to
early hypotheses
eggshells,
but
was
effective for consuming
plants and crushing shells of animals, such as clams.
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Carnivores
Many dinosaurs in the prehistoric era were carnivorous,
meaning they hunted and ate meat as their food. These predators’
physiology
allowed
them
to
be
efficient and effective when hunting.
The
ability
to
hunt
the
large
herbivores was necessary for survival.
Because they relied on their ability to
hunt, chase, and kill other animals,
their physiology became adapted to
such
requirements.
As
these
dinosaurs developed, they evolved to
become
the
most
dangerous
creatures on land.
Spinosaurus, the largest known carnivorous
dinosaur at 17 meters long
Dinosaurs hunted in some ways
similar to those of modern
reptiles.
Carnivores
needed sharp and deadly
tools to kill their prey,
which is why most had
large, sharp teeth and
claws. Some, specifically
Velociraptors, developed
one large
An example of a Velociraptor claw with its
measurements
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Carnivores
sickle-shaped claw on each of its hind feet. This claw, which could
be over six centimeters long, was raised while running to provide
little resistance to the dinosaurs’ speed
and could be utilized for killing prey.
Did you know?
Carnivorous dinosaurs were often much
The smallest dinosaur,
larger
Anchiornis huxleyi, was
than
most
herbivores
and
omnivores. The smaller dinosaurs were
as deadly as the larger, especially when
the about size of a
pigeon. It was only 35
centimeters long.
they hunted in packs. Carnivores acted
very similarly to modern lions when they hunted. Solitary hunters,
such as T. rex, waited in hiding as a pack of other dinosaurs passed
by. The attacker would then sprint toward the back of the group,
where the slowest dinosaurs were.
Carnivorous dinosaurs were important to the prehistoric
ecosystem.
There
were fewer carnivores
than herbivores, but
their
hunting
prevented population
of
A fossil of a Velociraptor and Protoceratops locked in battle
herbivorous
dinosaurs from growing
rampantly.
Herbivores
required
numerous
plant
sources,
and
by
controlling the herbivore population, the carnivores kept the
ecosystem in balance. In turn, their reliance on other carnivores as
a food source kept their own population in check.
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Extinction
Scientists are still unsure what caused dinosaurs to become
extinct; however, there are some valid hypotheses. Some scientists
support the idea that an asteroid collided with the earth and caused
a long nuclear winter. There is a 180-kilometer wide crater located
in the Gulf of Mexico that scientists think was caused by the impact
of the asteroid. Despite this evidence, some scientists theorize that
the extinction was caused by volcanic eruptions, sea level changes,
and climate changes.
An estimated 75% of all species on earth became extinct during
this event, including all non-avian dinosaurs, which were the
dinosaurs that could not fly. Scientists speculate that these animals
ran out of food and starved. However, they do not know if the
extinction occurred gradually or suddenly.
supporting both gradual and sudden extinctions.
There is evidence
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Birds
The bird-like dinosaurs survived the mass extinction, which
allowed for further evolution. Scientists theorize that some birds
today, such as chickens, evolved from avian dinosaurs.
Some
dinosaurs, such as Anchiornis huxleyi, had feathers, which supports
this theory.
Scientists also classify dinosaurs according to their
skeleton type: bird-like or lizard-like. Some herbivorous dinosaurs
had a mouth structure that was similar to the common bird today.
In addition, the skeletons of some dinosaurs resembled those of
modern birds.
There is behavioral evidence that birds are descendants of
dinosaurs. Fossils of Sinornithiodes indicate that dinosaurs slept
with their heads tucked under their arms, as modern ostriches do.
In addition, there are fossils that show evidence of soft-tissue
structures, such as lungs, that are similar to modern birds’ organs.
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Glossary
amniotic eggs- eggs that do not require water and have a hard shell
bipedal- uses two legs to walk
Canine teeth- sharp, pointed teeth used for tearing meat
carnivores- animals that only eat meat
Dinosaur- group of reptilian animals from the prehistoric era that
became extinct
Ecosystem- a community of organisms and their environment
gastroliths- stones that dinosaurs would swallow to churn food in
their stomach
non-avian- dinosaurs that do not fly
herbivores- animals that only eat vegetation
omnivores- animals that eat both meat and vegetation
paleontologists- scientists that study prehistoric animals
Physiological- pertaining to the functions of organisms and their
parts
Sickle-Shaped- crescent shaped
terrestrial animals- animals that live on land
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Image Credits
Cover- http://www.blirk.net/dinosaurs-wallpaper/4/1680x1050/
Page 2- http://www.freeimageslive.co.uk/files/images006/
Page 3- http://upload.wikimedia.org/wikipedia/commons/3/39/
http://geochristian.files.wordpress.com/2008/10/dinoridge-tracks.jpg
Page 4- http://1.bp.blogspot.com/bs6Y4q1Gi4I/UPBboCV3nsI/AAA AAAAAP6Y/BkCqA_KBTRs/s1600/800pxMaiasaura_Nest _Model.001_Page 5- http://www.kidsdinos.com/images/dinosaurs/Brachiosaur us1140906630.jpg
http://1.bp.blogspot.com/_1f8qaegCiyU/S5egU7z0dAI/AAAAAAAABgY/gmHG01D8pnk/s400/gastrolit
hs.jpg
Page 6- http://3.bp.blogspot.com/-h0ZMvi6W0Vo/TjWtvOTPcgI/A AAAAAAAASc/hHpbiFEs3H4/s
http://img.geocaching.com/cache/91c965da-5761-4aac-a32e-14b1f873fb1c.jp
Page 7- http://animal.discovery.com/dinosaurs/heterodontosaurus .htm
Page 8- http://jarek-boxjellyfish.blogspot.com/2011/10/oviraptor .html
Page 9- http://www.kidsdinos.com/dinosaurs-for-children.php?din osaur=Spinosaurus
http://australianmuseum.net.au/image/Velociraptor-claw
Page 10- http://www.baystatereplicas2.com/wp-content/uploads/2013/03/DINO_veloprotofighting_GASTON.jpg
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About the Authors
Leighton Moylan is a senior at Mass Academy of Math
and Science. He enjoys writing both books and music.
In his spare time he likes to play football and the
guitar. Leighton is an avid dinosaur enthusiast and is
ecstatic to have worked on this project.
Olivia Silva is senior at the Mass
Academy of Math and Science.
She loves writing, sailing, and
skiing. In her free time, she
enjoys drawing and reading. She
had a wonderful time writing this
book.