by Kessie Carroll

Created on: April 07, 2009   Last Updated: April 08, 2009

There are many similarities between dinosaurs and birds. There are also just as many differences.

Some large theropods, like the allosaurus, have been recently discovered to have air sacs around their lungs. Since allosaurs are far too big to be otherwise related to birds, and show no signs of having feathers, scientists think that the allosaur's air sacs were not only to help it breathe better, but to help it cool off.

Extremely weird "dinosaurs" with feathers are being discovered all the time. For instance, Epidexipteryx hui, discovered in Inner Mongolia, China, has four long tail feathers that don't appear to have a feather shaft. Scientists are puzzled by this and don't know where to put this in the evolutionary tree.

Another recent discovery is Gigantoraptor erlianensis, a huge beaked "dinosaur" that walked on two legs, stood more than 16 feet tall, and weighed more than 3000 pounds. It had feathers on its arms, but there wasn't enough of the fossil to know if the creature's body was covered, as well. Many of its smaller relatives had feather-covered bodies, much like the hair-like feathers that emus have today.

In 1990, a dinosaur nest was discovered in Montana. It belonged to a caenagnathid, a member of emu-like dinosaurs. The nest was a mound in moist sand, which the mother dug out while shaping the nest. The eggs were laid on the sides of the mound like the spokes of a wheel, and apparently the mother remained at the top of the mound to brood her eggs.

Discovery of Buitreraptor gonzalezorum, a member of the same family as Velociraptor, threw the dinosaur-bird evolution time line into a corkscrew. It was discovered in South America, and in a deeper layer of rock strata. It means that these "bird-dinosaurs" were around much earlier than scientists had thought.

Yet another bizarre creature was Microraptor. It had fully-developed wings, but it also had long feathers on its hind legs, leading scientists to believe that it flew or glided like a biplane.

They estimate that it lived in the treetops, and dove off branches, opening its wings, and gliding to the next branch, its legs hanging down, helping provide lift. This caused discussion among scientists as to whether flying dinosaurs started on the ground and moved to the trees, or started in the trees and moved to the ground.

There are so many "feathered dinosaurs" that scientists no longer question that birds evolved from dinosaurs. However, each new discovery confuses this theory more and more, because there is no clear evolutionary path between modern birds and ancient bird-like creatures.

All we have are the facts: there were creatures in the past with feathers that looked sort of like birds and sort of like lizards. Some had beaks and some had jaws with teeth. Perhaps the facts have been misinterpreted ... perhaps instead of calling all these animals "bird-like dinosaurs", perhaps we should call them "birds".

There have never been any fossils found of feathers halfway through evolution; scales shredding at the end and breaking into filaments, for example. Feathers appear in the fossil record completely formed. The bird-like creatures in the fossil record were not half-evolved. Whether ground-bound or able to fly, each new creature discovered was perfectly designed for its unique environment.

Perhaps scientists need to rethink their own confusing theory through which they interpret these facts.

References:
http://www.livescience.com/animals/ 081022-feathered-dinosaur.html
http://www.livescience .com/animals/070613_dino_bird.html
http://dsc.discove ry.com/news/2008/11/13/dinosaur-egg-nest.html
http:// news.bbc.co.uk/2/hi/asia-pacific/4337888.stm
http://w ww.livescience.com/animals/051014_flying_dino.html

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