Leighton Moylan and Olivia Silva

Transcription

1 DINOSAUR BEHAVIOR Leighton Moylan and Olivia Silva

2 Table of Contents 1 Introduction Classification Herbivores Omnivores Carnivores Extinction Birds Glossary Image Credits About the Authors

3 Introduction 2 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 on the dinosaurs diets. Herbivores only ate plants, carnivores only ate meat, and omnivores ate both plants and meat. Scientists who study prehistoric animals, such as 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 thought dinosaur fossils were dragon bones and used them to make medicine. The first recognized dinosaur fossils were found in England. Small dinosaur fossils dinosaur skeletons and traces (such as footprints and feces).

4 Introduction 3 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 have discovered over 1,000 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

5 Classification 4 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 with common reptiles, which allows scientists 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.

6 Herbivores 5 Paleontologists have discovered numerous herbivore dinosaur fossils. They are easily identifiable because of their distinguishing physiological features. Herbivorous dinosaurs had teeth for consuming plants, which were much different from those of carnivorous dinosaurs. The most well known herbivorous dinosaurs are the 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. Sauropods had t e Examples of gastroliths The Brachiosaurus, a type of Sauropod 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.

7 Herbivores 6 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 small bipedal organisms, but they eventually evolved into larger quadrupedal animals. 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

8 Omnivores 7 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 dinosaurs were medium sized 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.

9 Omnivores 8 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 The Oviraptor, which was not an egg hunter, contrary to early hypotheses plants and crushing shells of animals, such as clams. 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 eggshells, but was effective for consuming

10 Carnivores 9 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. Dinosaurs hunted in some ways Spinosaurus, the largest known carnivorous dinosaur at 17 meters long 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

11 Carnivores 10 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. Carnivorous dinosaurs were often much larger than most herbivores and omnivores. The smaller dinosaurs were as deadly as the larger, especially when they hunted in packs. Carnivores acted Did you know? The smallest dinosaur, Anchiornis huxleyi, was the about size of a pigeon. It was only 35 centimeters long. 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 herbivorous A fossil of a Velociraptor and Protoceratops locked in battle 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.

12 Extinction 11 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. There is evidence supporting both gradual and sudden extinctions.

13 Birds 12 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.

14 Glossary 13 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

15 Image Credits 14 Cover- Page 2- Page Page 4- AAAAAP6Y/BkCqA_KBTRs/s1600/800px- Maiasaura_Nest _Model.001_- Page 5- us jpg hs.jpg Page 6- AAAAAAAASc/hHpbiFEs3H4/s Page 7- Page 8- Page 9- osaur=spinosaurus Page 10-

16 About the Authors 15 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.