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Bird Evolution
Melanie Lewis
Historical Geology
Spring 2006

                                 The Birds and The Beasts


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Where do birds really come from?  Who are there ancestors?  What did they look like in

the past?  Could it really be possible for a Hummingbird and a T-Rex to have been related?  These answers may astound you for this connection might not be so far off.



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The idea of a common link between the extinct dinosaurs and the modern day avian species was far from anyone's mind in the scientific community until about one century ago.  Due to the large gap in fossil records between the Cretaceous and the late Oligocene periods this theory was unimaginable.  The first hints that birds may be descendants of dinosaurs came in 1861.  After the discovery of an unusual looking fossil in a Limestone formation, called the Solnhofen Formation in Germany, it became clear that a species once existed which had been a transitional form between two vertebrate groups.  This fossil, also known as the Archaeopteryx lithographica was a creature in between a traditional reptile and a bird.


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Archaeopteryx was a crow sized animal that shared traits with both reptiles and birds.  In addition it had a snout similar to that of a reptile, teeth, and asymmetrical feathers similar to today's common birds.  There are six skeletal specimens of Archaeopteryx known to us today.  Some where located in the years 1861, 1956, and 1987.  A seventh specimen was found, however, it consisted only of a stray feather imprint. 




Unlike the modern bird, Archaeopteryx shared some primitive traits with dinosaurs and other reptiles. Some similarities between these creatures were the teeth in the jaw, a snout rather than a beak, and abdominal ribs.  They also shared long forelimbs, claws, and a long balancing tail, although the tail was decreasing in the Archaeopteryx and therefore shorter than that of the dinosaurs and reptiles.





In addition to the apparent physical similarities, the Archaeopteryx also shared developmental traits with the dinosaurs and reptiles.  After hatching and reaching their mature state, birds no longer grow or develop further.  On the contrary, dinosaurs and reptiles continually mature over a large period of time.  From the specimens of Archaeopteryx that were found many were of different sizes and maturity, which led scientist to speculate over anything from possible breaks in species to simple age differences. 


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Although some fossils of early birds have been found to have left no feather impressions behind, most of the early birds had feathers.  Not all animals with feathers, however, are related to or the predecessors of birds.  There were many dinosaurs that had what are called vane feathers, which are feathers with a shaft, vane, and barbs.  These feathers, which might have later led to the larger feathers used for flying, were used for giving balance, keeping warm, and impressive courting displays. 


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The discovery of the feathered Archaeopteryx fossil brought about the theory of birds evolving from dinosaurs.  However, the true leading force behind the dino-bird theory for today's scientists comes from the fossils and the skeletal similarities shared by the two groups and not the commonality of feathers alone.