Advertisement.

EnchantedLearning.com is a user-supported site.
As a bonus, site members have access to a banner-ad-free version of the site, with print-friendly pages.
Click here to learn more.

ad
(Already a member? Click here.)

ZoomDinosaurs.com
ALL ABOUT DINOSAURS!
What is a Dinosaur? Dino Info Pages Dinosaur Coloring Print-outs Name That Dino Biggest, Smallest, Oldest,... Evolution of Dinosaurs Dinos and Birds Dino Myths


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, in some instances, 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):




Enchanted Learning®
Over 35,000 Web Pages
Sample Pages for Prospective Subscribers, or click below

Overview of Site
What's New
Enchanted Learning Home
Monthly Activity Calendar
Books to Print
Site Index

K-3
Crafts
K-3 Themes
Little Explorers
Picture dictionary
PreK/K Activities
Rebus Rhymes
Stories
Writing
Cloze Activities
Essay Topics
Newspaper
Writing Activities
Parts of Speech

Fiction
The Test of Time
iPhone app
TapQuiz Maps - free iPhone Geography Game

Biology
Animal Printouts
Biology Label Printouts
Biomes
Birds
Butterflies
Dinosaurs
Food Chain
Human Anatomy
Mammals
Plants
Rainforests
Sharks
Whales
Physical Sciences: K-12
Astronomy
The Earth
Geology
Hurricanes
Landforms
Oceans
Tsunami
Volcano
Languages
Dutch
French
German
Italian
Japanese (Romaji)
Portuguese
Spanish
Swedish
Geography/History
Explorers
Flags
Geography
Inventors
US History

Other Topics
Art and Artists
Calendars
College Finder
Crafts
Graphic Organizers
Label Me! Printouts
Math
Music
Word Wheels

Click to read our Privacy Policy

E-mail


Enchanted Learning Search

Search the Enchanted Learning website for:



Advertisement.



Advertisement.



Advertisement.



Copyright ©1997 EnchantedLearning.com ------ How to cite a web page