where is the distinction between them made? If it had feathers was it a dinosaur or bird? Did it have to fly for a certain length of time to be considered a bird? What if the dinosaur had feathers and glided?
I doubt it has anything to do with the ability to fly. Look at an ostrich; that can't fly, yet it is a bird.
Well, dinosaurs were classified as such because the skeletons that were initially found were nothing like any living creature that exists now. As more and more fossilized remains are found, we begin to see more and more similarities between organisms that lived then and those we can see alive today. Calling them "dinosaurs" is an arbitrary name that we as humans gave them. But, the distinction is made on more than just outward appearance or the ability to fly. Pterosaurs could fly, but would you consider those to be birds? There are other physiological traits that need to be considered as well -- bone structure, reproduction, etc. I'm not big into taxonomy, personally, so I may not be able to answer as clearly as some of the others (wait for Fraggle...), but it's a very complex process.
Since birds are considered flying critters, I would imagine that we'll say that it was still a dinosaur if it could not fly [either glide or self-powered]. Thus, there is a series of dinosaurs that had feathers, but were not technically birds. I believe that Archaeopteryx is still considered the oldest bird, though there might be more primitive birds that will be discovered.
what made it a bird and not a flying dinosaur? Was it because ti had feathers? If it flew and had feathers it was no longer a dinosaur, but a bird?
Orly, sometimes you ask questions that are far beyond the scope of an answer we can reasonably compose on SciForums. I suggest you read the Wikipedia articles on the origin of birds and the evolution of birds, and, for good measure, plain old birds. This subject is far more complicated than you give it credit for, and there's also a bit of controversy involved. Your questions are so oversimplified that they condense out some of the key issues in the relationship between birds and dinosaurs. There's no easy way to answer them because they're not the right questions. I've heard scientists answer, in exasperation, "Birds are dinosaurs." That statement is not false, it's just not complete. Ostriches are surely birds. They're members of an order called the ratites. The ratites have no "keel" on their sternum (breastbone) so there's nothing to anchor powerful wing muscles to. Even if they had appropriate-sized wings, they couldn't fly. Besides, if a 350-pound ostrich could fly, how large do you suppose its wings would have to be, considering that the condor, weighing a mere 25 pounds, has a ten-foot wingspan? The other eight species of ratites are, in order of size, the emu, the cassowary, the rhea, and the five kiwis. At 45mph, the ostrich is the fastest animal that runs on two legs. Oh BTW, penguins don't fly either.Please Register or Log in to view the hidden image!
I wouldn't be so sure about that.... Please Register or Log in to view the hidden image! Flying penguins found by BBC programme
I think Fraggle's statement that penguins do not fly (in air anyway, under water, perhaps. It depends on the definition of flying.) is safe. I note your BBC counter example came out on 1 April. I recall a wonderful BBC 1April news release on the Italian spaghetti harvest. It was a TV "documentary" with ladies in Italian looking clothes up on ladders, cutting the ripe spaghetti from the trees. BBC has a sense of humor, occasionally.
Maybe smaller cat-sized dinosaurs took to the trees for protection from the bigger meat-eaters on the ground and as a result, they slowly over millions of years, evolved into birds-like dinosaurs with feathers and all.
The puffin, I believe, actually uses its wings for propulsion and can be seen going through the motion of "flying" under water. The wing motions are very slow, of course, because the viscosity of water is much greater than air. It's like a slow-motion video of flight. Other birds use their wings as well. I saw a video of a parrot who had fallen in the water and he instinctively "flew" to safety. But penguin wings have shrunk and are not useful for propulsion. They're steering fins. They propel themselves with their gigantic feet.
The taste! One tastes just like chicken and the other really sticks to your ribs and is very meaty tasting.Please Register or Log in to view the hidden image!
A fully-fused collarbone, perhaps? The OP seems to be misunderstanding the purpose of the taxonomic classification system, and I feel that is the fault of how it has been explained to the general populace. Taxonomy does not equate to a Truth about the natural world, it's just a collection of buckets we dump things into, usefully organizing life into named groups so that we can talk about them more easily. In the real world, there is almost certainly an unbroken family line from theropod dinosaurs to birds; at each end of that line it is easy to classify any particular specimen as either dino or bird; everything in the middle, however, is not so simple. These groups aren't hard-walled divisions that actually exist in nature, they are just labels. As such, there are many individual organisms that kinda fit in more than one groups, based on different features. A species of dinosaur found in China last year had feathers, but did not have a fused breastbone. Archeopteryx had feathers and wings structured like modern birds, but also had teeth. http://en.wikipedia.org/wiki/Feathered_dinosaurs
As for the question of how flight itself arose, I'd say that being able to run up steep inclines may have been part of the benefit. http://www.youtube.com/watch?v=e81J915TEXg http://www.youtube.com/watch?v=5Rjin-tjOxU&feature=related Also of benefit may have been the ability to fall *slightly* slower from out of a tree, and thus not break a leg upon landing. http://www.youtube.com/watch?v=FhDQvRBngkQ&feature=related
I am sure you are correct on this, but surely you do not want to limit the concept of "flying" to objects which overcome the fluid (air or water) friction by motion of their wings. I.e. it does not matter that the penguin's "propulsion" is achieved without use of the wings. If you think it does, then you must think a fighter jet with stubby wings does not "fly." An even stronger example is the Tomahawk cruise missile. It can fly 1000 miles and its four tiny wing (roughly triangle shaped and spaced every 90 degrees around the lift center of the body) are so small they are entirely folded inside the cylindrical body when launched from a submarine. I think they can be, but usually are not, launched from the torpedo tubes, and then first fly under water to the surface. Propulsion via the wings, or even the total absence of any propulsion, as in a glider or soaring hawk, is not required for "flying." While many may not want "flying" to include underwater motion, everyone believes that many objects, both natural and man-made, fly without using wings for propulsion.
...The earliest known species of class Aves is Archaeopteryx lithographica, from the Late Jurassic period, though Archaepteryx is not commonly considered to have been a true bird.... What is a true bird?
They would most likely be considered bird ancestors and not true, modern birds, yes. I would not expect them to be called pre-birds however, because that term suggests that they are lacking something, or not yet fully formed organisms in their own right. They were individual living things with features that helped them survive. They were perfectly suited to their environment at the time - they were what they were; we call them dinos with feathers. They have a number of dinosaur features we don't think of when considering birds: teeth, clawed digits on the upper limbs, long bony tails. Some specimens also have a number of features that are very modern bird-like: feathers, beaks, bird-like foot/ankle bones, keeled sternums. They also have some noticeable proto-bird features: the feathers are symmetrical, which is not seen in flying birds today; the asymmetrical vanes and curve seen in modern bird flight feathers appear to be a critical aspect of bird flight; shallowly keeled sternums for attaching larger breast muscles. I just found an open copy of the textbook "Vertebrate Paleontology" on googlebooks; check out this chapter on the origin of bird flight: http://books.google.com/books?id=P1...X&oi=book_result&resnum=6&ct=result#PPA261,M1 I recommend everyone interested in evolution read that book.
The largest bird that can fly at all is a species of bustard weighing only around forty pounds (17kg). The largest bird that can actually maintain a maneuvable flight and fly the way we expect birds to fly is the condor. It weighs only 25 lb (12kg) and requires a ten-foot (3m) wingspan to accomplish that. Remember that mass increases as the cube of linear dimension, whereas the surface area of a wing (or any other body part) increases only as the square. If you increase a bird's length by a factor of two, you increase its mass by a factor of eight. If its wings were proportional, their surface area would only increase by a factor of four and they would not be able to support the weight. So the wings have to be disproportionately larger in comparison to the body. This is why tiny birds like hummingbirds and chickadees have wings that are a little smaller than their bodies, whereas big birds like macaws and eagles have wings that comprise the majority of their silhouette when flying. In order for a 300 lb (135kg) ostrich to fly, it would need a wingspan of about eighty feet (25m). I'll let you do the math on a one-ton dinosaur. Please Register or Log in to view the hidden image!
