All about Dinosaurs

[dream girl]

All about Dinosaurs
​

What is a Dinosaur?
Millions of years ago, long before there were any people, there were dinosaurs. Dinosaurs were one of several kinds of prehistoric reptiles that lived during the Mesozoic Era, the "Age of Reptiles."

Dinosaurs were reptiles and most hatched from eggs. No dinosaurs could fly and none lived in the water.

Plant-eating sauropods were the largest animals to ever walk on Earth - but blue whales are more massive than any of the dinosaurs were! The largest dinosaurs were over 100 feet (30 m) long and up to 50 feet (15 m) tall (like Argentinosaurus, Seismosaurus, Ultrasauros, Brachiosaurus, and Supersaurus). The smallest dinosaurs, like Compsognathus, were about the size of a chicken. Most dinosaurs were in-between. It is very difficult to figure out how the dinosaurs sounded, how they behaved, how they mated, what color they were, or even how to tell whether a fossil was male or female.

No one knows what color or patterns the dinosaurs were.
Most dinosaurs were plant-eaters (also called herbivores). For example, Triceratops was a plant-eating dinosaur.


Some dinosaurs were meat-eaters (also called carnivores). For example, T. rex was a meat-eating dinosaur. There were lots of different kinds of dinosaurs that lived at different times.

• Some walked on two legs (they were bipedal), some walked on four (they were quadrupedal). Some could do both.
• Some were speedy (like Velociraptor), and some were slow and lumbering (like Ankylosaurus).
• Some were armor-plated, some had horns, crests, spikes, or frills.
• Some had thick, bumpy skin, and some even had primitive feathers.

The dinosaurs dominated the Earth for over 165 million years during the Mesozoic Era, but mysteriously went extinct 65 million years ago. Paleontologists study their fossil remains to learn about the amazing prehistoric world of dinosaurs.

When the dinosaurs lived, the Earth's continents were jammed together into a supercontinent called Pangaea and the Earth was warmer than it is now.

The dinosaurs went extinct 65 million years ago, probably because of the environmental changes brought about by an asteroid hitting the Earth.

The dinosaurs went extinct about 65 million years ago, at the end of the Cretaceous period, which was a time of high volcanic and tectonic activity. There are a lot of theories why the extinction occurred. The most widely accepted theory is that an asteroid impact caused major climactic changes to which the dinosaurs couldn't adapt.

Dinosaurs probably live on today as the birds. All that's left of the dinosaurs are fossils and, perhaps,the birds. Dinosaur fossils have been found all over the world, maybe even near where you live!

Some dinosaurs were very bird-like and may be the ancestors of today's birds.

There are almost 500 described dinosaur genera and many more species. Every few months (sometimes weeks), new finds are unearthed.

Although dinosaurs' fossils have been known since at least 1818, the term dinosaur (deinos means terrifying; sauros means lizard) was coined by the English anatomist Sir Richard Owen in 1842. The only three dinosaurs known at the time were Megalosaurus, Iguanodon, and Hylaeosaurus, very large dinosaurs.

The oldest known dinosaur is Eoraptor, a meat-eater from about 228 million years ago.

 

[dream girl]

Name That Dino:
What Does the Word Dinosaur Mean and How are Dinosaurs Named? Greek, Latin, and other roots used in dinosaur names

Sir Richard Owen coined the word dinosaur, meaning "fearfully great lizard," in 1842. In Greek, "deinos" means "fearfully great" and "sauros" means "lizard."

Newly discovered dinosaurs are named by the discoverer or by the paleontologist who determines that it represents a new genus. There are many different ways to choose a dinosaur name. Sometimes the dinosaur is given a name that describes something unusual about its body, head, or feet. Some are named after the location where they are found, others are named for their behavior or size, and some are named to honor a person. The name has to be approved by the International Commission on Zoological Nomenclature.

Dinosaur Evolution

Dinosaurs evolved from other reptiles (socket-toothed archosaurs) during the Triassic period, over 230 million years ago. Dinosaurs evolved soon after the Permian extinction, which was the biggest mass extinction that ever occured on Earth. During this time (the Triassic period), the mammals also evolved.

Dinosaur timeline

Thecodonts: Crocodile-like Archosaurs:
Chasmatosaurus
Chasmatosaurus, a crocodile-like, meat-eater (a thecodont) from the Triassic period.
Thecodonts may have been ancestors of the dinosaurs. Thecodonts (like Chasmatosaurus) were socket-toothed reptiles that were the ancestors of dinosaurs, birds, pterosaurs, and crocodilians. These archosauriforms were low-slung, meat-eating quadrupeds had long jaws and a long tail (they looked a lot like crocodiles).

Reptilia cladogram

This is a cladogram of the clade Reptilia (reptiles), tracing the ancestry of these groups.


The Earliest Dinosaurs:
The first dinosaurs were small and lightly built, mostly about 10-15 feet long (3 to 4.5 m). They were bipedal carnivores or omnivores, and probably very agile and fast.

The world's oldest-known dinosaurs have been found on Madagascar, an island off the coast of SE Africa. These dinosaur fossils date from about 230 million years ago during the Triassic period.

EoraptorUntil recently, the earliest-known dinosaur was Eoraptor lunensis (meaning"dawn raptor") which lived about 228 million years ago. It was a small, primitive theropod (a bipedal meat-eater) about 3 feet (1 m) long. It lived in what is now Argentina, South America (fossils were found at the Ischigualasto Formation).

 

[dream girl]

Debunking Dinosaur Myths
Do you know the answers to these dinosaur questions? Don't rely on popular images from dinosaur movies or cartoons! They're frequently wrong.

1. 
   
   [*]Were all huge, prehistoric animals dinosaurs?
   [*]Did any dinosaurs swim or fly?
   [*]Were all the dinosaurs huge?
   [*]Did cavemen live alongside the dinosaurs?
   [*]Did all the dinosaurs live at the same time?
   [*]Did all the dinosaurs die out?
   [*]Why were the dinosaurs a failure?

1. Not all huge prehistoric animals were dinosaurs.

A lot of animals existed during the Mesozoic along with the dinosaurs. Some animals were closely related to the dinosaurs, like the pterosaurs (which belong to the Order Archosauria as do the dinosaurs). Birds, however, are dinosaurs! Other animals, like the Dimetrodon, which lived in the Paleozoic era before the dinosaurs existed, are more closely related to us than to the dinosaurs.

2. There were no flying dinosaurs or swimming dinosaurs.

All dinosaurs lived on the land; none of them lived in the seas or flew (until the birds)! Neither the flying pterosaurs, nor the swimming ichthyosaurs were dinosaurs, although all were closely related. Some advanced meat-eating dinosaurs did develop feathers, and evolved into birds.


3. Not all dinosaurs were huge.

There were plenty of small and medium-sized dinosaurs. The smallest dinosaur yet discovered is Compsognathus, which was the size of a chicken!

4. People did not coexist with the dinosaurs (except for the birds).

Although the image of human cave dwellers hunting dinosaurs is well established in fiction, it is far from accurate. People didn't evolve until about 65 million years after the dinosaurs' extinction. Except for the birds, who are the sole surviving descendants of the dinosaurs, the dinosaurs and people are well separated in terms of geologic time.

5. The dinosaurs didn't all live at the same time.

The dinosaurs roamed the Earth for about 165 million years. Different types of dinosaurs existed at different times. Dinosaur species evolved and went extinct throughout the Mesozoic (this is called background extinction).

In the Triassic period, the early dinosaurs were small, and most species died out in an extinction at the end of the Triassic period. In the Jurassic, many new dinosaur species evolved from the Triassic survivors, including the gigantic sauropods (like Apatosaurus

and Seismosaurus), Allosaurus

, and Stegosaurus

, to list but a few. Dinosaurs reached the height of their diversity during the Cretaceous; monstrous giant theropods (like T. rex and Giganotosaurus), Ankylosaurus

, Maiasaura

and many other dinosaurs lived during that period. Despite popular images to the contrary, Stegosaurus never encountered T. rex.

6. Not all the dinosaurs died out 65 million years ago.

Most of the dinosaur groups went extinct long before the K-T mass extinction of 65 million years ago. The remaining dinosaurs died out at that time, but many bird species (which are technically dinosaurs) survived it.

7. The dinosaurs were not a failure.

Various dinosaurs lived all around the Earth for about 165 million years. In comparison, people have only been around for about a million years. In terms of survival through geological time, the dinosaurs were long-lasting animals, probably leaving birds as their descendants.

 

[dream girl]

DINOSAURS and BIRDS

Birds probably evolved from the maniraptors, a branch of bird-like dinosaurs . This idea has been hotly debated for over a hundred years. New fossil evidence is reinforcing this theory, which is now accepted by most scientists.

In order to determine what animals birds evolved from, scientists use fossil evidence to trace the emergence of bird-like traits. Many Mesozoic Era bird-like creatures have been found, some which are clearly dinosaurs. There are many similarities between birds and theropod dinosaurs, including the number of openings in the skull (they're diapsids), secondary palate structure, leg and foot structure and proportions, upright stance, oviparous birth (laying eggs), bone structure (bones interlaced with vessels), and scales (modified in birds and some dinosaurs to be feathers).

Recently, scientists have reorganized the groups in which many animals have been classified using a system called cladistics. Since birds are descended from dinosaurs, they are in the same group, dinosauria. So the national symbol of the United States is actually a dinosaur (the bald eagle).

FEATHERED, BIRD-LIKE DINOSAURS
In the last few years, many fossils of feathered dinosaurs have been found near Yianxin, in Liaoning Province, China. Two new Chinese feathered dinosaurs dating from between 145 and 125 million years ago (during the late Jurassic and early Cretaceous periods) have been found, Protarchaeopteryx robusta and Caudipteryx zoui. Their features are more dinosaur-like than bird-like, and they are considered to be theropod dinosaurs. Their feathers were symmetrical, which indicate that they could not fly (flightless birds have symmetrical feathers while those that fly have asymmetrical ones).

These finds, along with the feathered dinosaur Sinosauropteryx, found a few years ago, also in the same region of China, and the bird-like Unenlagia in Argentina, reinforce the theory that birds are descended from dinosaurs.

THE OLDEST-KNOWN BIRDS

The Archaeopteryx is one of the most famous and oldest-known fossil birds, and dates from the late Jurassic period (about 150 million years ago). It is now extinct. Although it had feathers and could fly, it had similarities to dinosaurs, including its teeth, skull, and certain bone structures. Some paleontologists think that Archaeopteryx was a dead-end in evolution and that the maniraptors led to the birds.

The first Archaeopteryx fossilized feather

impression was found in 1860 in a limestone quarry in Germany. A year later, a much more complete fossilized Archaeopteryx was found at the same quarry. Impressions of its feathers and bone structure were quite clear. Many more have been found since, for a total of seven.

In 1868, Thomas Henry Huxley interpreted the Archaeopteryx fossil to be a transitional bird having many reptilian features. Using the fossils of Archaeopteryx and Compsognathus, a bird-sized and bird-like dinosaur, Huxley argued that birds and reptiles were descended from common ancestors. Decades later, Huxley's ideas fell out of favor, only to be reconsidered over a century later (after much research and ado) in the 1970's. In 1986, J. A. Gauthier looked at over 100 characteristics of birds and dinosaurs and showed that birds belonged to the clade of coelurosaurian dinosaurs. [Gauthier, J.A., 1986. Saurischian monophyly and the origin of birds, in The Origin of Birds and the Evolution of Flight, California Academ of Sciences Memoir No. 8]

Bird fossils are rare because bird bones are hollow and fragile, but Jurassic, Cretaceous, Eocene and Miocene-Pliocene bird fossils have been found.

BIRD-LIKE ANIMALS
In the chain of creatures leading from dromaeosaurid dinosaurs (advanced theropods) to birds, Sinosauropteryx is the earliest bird-like dinosaur. For now, the bird-like animals include (in chronological order):

• 
  
  [*]Protoavis (meaning "first bird") is an extinct diapsid from the late Triassic period (80 million years earlier than Archaeopteryx). Its partly toothless jaw and keel-like breast bone were like those of birds. It also had a tail, dinosaur-like rear legs, and hollow bones. There is some dispute about whether this animal was a bird or a dinosaur; the answer depends partly on whether the Protoavis fossil belongs to one or two different genera. Fossils have been found in Texas, USA.
  [*]Archaeopteryx - The oldest known bird had asymmetrical feathers - it could probably fly short distances and was the size of a crow. This bird was probably an evolutionary dead-end. (from Germany, 150 million years ago).
  [*]Sinosauropteryx - Sinosauropteryx had a coat of downy, feather-like fibers that are perhaps the forerunner of feathers. This ground-dwelling dinosaur had short arms, hollow bones, a three-fingered hand, and was about the size of a turkey. (from China, 121-135 mya).
  [*]Protarchaeopteryx - Long, symmetrical feathers on arms and tail, but it probably could not fly. It was the size of a turkey (from China, 121-135 mya).
  [*]Caudipteryx - a small, very fast runner covered with primitive (symmetrical and therefore flightless) feathers on the arms and tail, with especially long ones on the tail. It was about the size of a turkey. (from China, 121-135 mya)
  [*]Iberomesornis (meaning "Iberian=Spanish intermediate bird") was a small, early, toothed bird that lived during the early Cretaceous period. It was capable of powered flight. It had tiny, spiky teeth in its beak and was the size of a sparrow. Its hip was primitive compared to modern birds; its ilium, ischium, and pubis were all parallel and directed backward. Iberomesornis was named by paleontologists Sanz and Bonaparte in 1992. Fossils were found in Spain. The type species is I. romeralli.
  [*]Unenlagia - a much larger ground-dwelling theropod about 4 feet (1.2 m) tall and 8 feet (2.4 m) long. It had flexible arm movement (up and down movements were possible, like that which a bird uses in flying). (from Argentina, 90 mya).
  [*]Patagonykus (meaning "Patagonia claw") was a lightly-built meat-eater with a single, clawed finger on each hand. It was about 6.5 ft (2 m) long. It had long legs, a long tail, and short arms. Patagonykus lived during the late Cretaceous period, about 90 million years ago. Patagonykus was either a bird-like dinosaur (an advanced theropod, or a primitive bird; it possessed qualities of both groups of animals, and there is much scientific debate over which it is. Patagonykus was similar to Mononykus. Fossils were found in Patagonia, a region of southern Argentina. The type species is P. puertai. Patagonykus was named by paleontologist F. Novas in 1996
  [*]Velociraptor - a larger, ground-dwelling carnivore with a swiveling wrist bone (this type of joint is also found in birds and is necessary for flight). About 3 feet tall (1 m). (from Mongolia, 85 - 80 mya).
  [*]Mononykus (meaning "single claw") was a small, insect-eater from the Late Cretaceous period, about 72 million years ago. Mononykus was either a bird-like dinosaur (an advanced theropod, or a primitive bird; it possessed qualities of both groups of animals, and there is much scientific debate over which it is. Mononykus had short arms with one long, thick clawed finger on each hand (hence its name). It was lightly built, had long, thin legs, and a long tail. Mononykus was roughly 28 inches (70 cm long). A fossil was found in SW Mongolia in 1923 (and originally called Mononychus). Mononykus was named by Perle, Norell, Chiappe, and Clark in 1993. The type species is M. olecranus.
  [*]Hesperornis (meaning "western bird") was an early, flightless bird that lived during the late Cretaceous period. This diving bird was about 3 feet (1 m) long and had webbed feet, a long, toothed beak, and strong legs. Although it couldn't fly, Hesperornis was probably a strong swimmer and likely lived near coastlines and ate fish. Fossils have been found in North America .
  [*]Ichthyornis (meaning "fish bird") were 8 inch (20 cm) long, toothed, tern-like, extinct bird that date from the late Cretaceous period. It had a large head and beak. This powerful flyer is the oldest-known bird that had a keeled breastbone (sternum) similar to that of modern birds. It lived in flocks nesting on shorelines, and hunted for fish over the seas. Ichthyornis was originally found in 1872 in Kansas, USA, by a member of paleontologist Othniel C. Marsh's Yale University expedition. Fossils have been found in Kansas and Texas, USA and Alberta, Canada. (Subclass Odontornithes, Order Ichthyornithiformes)
  [*]Eoalulavis (from Spain) - the earliest bird that had good maneuverability while flying, even at low speeds (this extra flight control is obtained from a tuft of feathers on the thumb called the alula - it also helps in takeoffs and landings).

 

[nrbhayo]

nice sharing