I want to have a science discussion or two...or many!

[Static_Martyr]

Archaeopteryx may be used as a model for a transition species, but it itself is not the transitional species, as true birds had already evolved by the time archaeopteryx was around. Therefore, it could not have been a transitional species.

Which birds are you saying evolved before Archaeopteryx? Do you have any species examples? There are a couple fossils commonly used as counterexamples to Archy, but they're misleading at best and are actually not classified as birds. From the TalkOrigins article I posted earlier:

Two species of dinosaur have recently been found in northeast China which possess feathers (Qiang et al. 1998). Protoarchaeopteryx robusta and Caudipteryx zoui show regiges, rectrices and plumulaceous feather inpressions. Further, they are not birds, lacking a reverted (backwards facing) big toe (see number 2 below) and a quadrratojugal squamosal contact, having a quadrojugal joined to the quatrate by a ligament and a reduced or absent process of the ishium. These and other characters group Protoarchaeopteryx and Caudipteryx with maniraptoran coelurosaurs rather than birds.

Systematics Note (from Padian 1998): Systematists define the names of organisms by their ancestry, in this case birds (Aves) consist of Archaeopteryx plus living birds and all the descendants of their most recent common ancester. Birds are diagnosed by unique features that only they possess and which are inherited from that common ancestor. Even if feathers are shared by a wider group than just birds, birds are still defined as Archaeopteryx and later relatives. Protoarchaeopteryx and Caudipteryx are not birds even though they have feathers because the suite of morphological characters they possess mark them as belong to the maniraptoran coelurosaur dinosarus.

In any case, the existence of similar traits in other populations doesn't necessitate that one evolved from the other (feathered theropods =/= birds, necessarily; they could be related, but phylogenetic similarity alone is an insufficient basis on which to determine which species evolved first, or whether they both evolved from a more distant common ancestor; you need more evidence to say for certain). It could easily be a case of convergent evolutions rather than divergent.

["Melyssa K" Kennedy]

No, I don't have a species name right now because no one ever wants to discuss these things with me, so I have not researched them in a long time. And I don't remember what it is because I was researching it for a school project years ago. I think it's likely that we will never know for sure because the fossil records are so incomplete. I'm sure someday in China we will unearth the true first bird and not even know it.

[Static_Martyr]

I think it's likely that we will never know for sure because the fossil records are so incomplete. I'm sure someday in China we will unearth the true first bird and not even know it.

Well, currently, "birds" are pretty much defined as "Archaeopteryx and its descendants," because it's the only fossil of its "type" to have the characteristics of birds that are necessary to indicate common descent to all modern birds. Other theropods had similar features (such as feathers), but they lacked the other features necessary to indicate a relation to modern birds (the toe being the best example).

And of course by nature the fossil record is incomplete, but then our picture of the different branches of descent comes (in part) from what we actually have of the fossil record. It's always possible that new discoveries will revolutionize the field or disprove currently-understood models, but that's nothing to worry about, as it happens all the time and is an expected part of the process. We don't make radical changes to our arrangements based on what could happen, but rather what does happen; and so if we do make such a discovery, then we will have to change the model accordingly, but until then we have a model that's also soundly based on current evidence.

["Melyssa K" Kennedy]

But Archaeopteryx is not a bird. It could not fly. It's sternum was far too small to be able to anchor the huge muscles necessary for flight. All birds either fly or have lost the ability to fly. Archaeopteryx and its ancestors could never fly. Though, they may have been able to glide, they lacked the musculature for active flight.

[Static_Martyr]

But Archaeopteryx is not a bird. It could not fly. It's sternum was far too small to be able to anchor the huge muscles necessary for flight. All birds either fly or have lost the ability to fly. Archaeopteryx and its ancestors could never fly. Though, they may have been able to glide, they lacked the musculature for active flight.

(1) Um, yes, studies indicate that Archaeopteryx was in fact almost certainly capable of some form of flight (either low flying or gliding, most likely). Its feathers are aligned to promote lift and are more consistent with flight feather patterns than contour patterns:

This study examines the morphology and function of hindlimb plumage in Archaeopteryx lithographica. Feathers cover the legs of the Berlin specimen, extending from the cranial surface of the tibia and the caudal margins of both tibia and femur. These feathers exhibit features of flight feathers rather than contour feathers, including vane asymmetry, curved shafts, and a self-stabilizing overlap pattern. Many of these features facilitate lift generation in the wings and tail of birds, suggesting that the hindlimbs acted as airfoils. A new reconstruction of Archaeopteryx is presented, in which the hindlimbs form approximately 12% of total airfoil area. Depending upon their orientation, the hindlimbs could have reduced stall speed by up to 6% and turning radius by up to 12%. Presence of the “four-winged” planform in both Archaeopteryx and basal Dromaeosauridae indicates that their common ancestor used fore- and hindlimbs to generate lift. This finding suggests that arboreal parachuting and gliding preceded the evolution of avian flight.

(2) ...you DO know what a "transitional form" is, right?

Look at it this way: wherever birds evolved from, if you go far back enough, you will find an ancestor that does not have wings. And I doubt that the first ancestor of birds to develop winglike appendages could fly. In fact, as in the above paragraph, it's commonly speculated that early birds could only glide, not fly. So it's actually sort of misleading to say that Archy isn't a bird because "all birds either fly or have lost the ability to fly," since they didn't really become "birds" as we understand them until after they had evolved the ability to glide and fly, and yet there had to be a species which did not have wings and later developed them. And Archy is supposed to demonstrate the transition between those states (it could fly/glide and had many features which link it to modern birds, but also could be tied to theropods and dinosaurs; hence, we say it's a "transitional form"). So your claim is semantically true, as *any* such classification is technically a tautology, but it's also cladistically irrelevant; we have to pick some reasonable boundary along the line in order to indicate where birds "begin" in the timeline, but we could just make other criticisms were we to draw the line somewhere else.

That said, taxonomical boundaries are somewhat arbitrary by nature and don't reflect the true flow of evolution (every member of a species is the same as its parent species, and so if we wanted to be technical, then we would have no basis on which to draw the species line definitively, because it would mean that one organism is one species while its offspring represents the "official" first member of the new species, meaning they are different species, which violates one of the primary rules of taxonomy). And so cladistically speaking, the tautology of saying "Archy is a bird because birds are defined as Archy and his descendents" is actually also the most reasonable way to establish the base of the family. That's just the issue with classifying transitional forms.

["Melyssa K" Kennedy]

Sir, before I read your reply, I am quite offended at your implication that I do not know what a transitional species/form is. So, I must inform you that, along with researching evolution for years throughout my childhood, I am a biology major aiming for a career as a paleontological reconstruction artist, have taken a general biology course, field biology, conservation ecology, biological principles I and II, wrote a research paper on convergent evolution and another on how cetaceans evolved to become marine mammals, as well as preparing a powerpoint on theropod evolution to birds to present at a student research conference and a literary review of the same subject. So, YES, I most certainly DO know what a transitional species/form is.

Gliding is not flying. Active flight require very powerful chest muscles, which in turn require a massive breastbone, as well as an efficient respiratory system and an impeccable sense of balance. The Archaeopteryx simply did not have the breastbone and muscles.

[Static_Martyr]

Sir, before I read your reply, I am quite offended at your implication that I do not know what a transitional species/form is. So, I must inform you that, along with researching evolution for years throughout my childhood, I am a biology major aiming for a career as a paleontological reconstruction artist, have taken a general biology course, field biology, conservation ecology, biological principles I and II, wrote a research paper on convergent evolution and another on how cetaceans evolved to become marine mammals, as well as preparing a powerpoint on theropod evolution to birds to present at a student research conference and a literary review of the same subject. So, YES, I most certainly DO know what a transitional species/form is.

With all due respect, I don't care what your credentials are, or that you're offended by my correction. I'm discussing facts, not credentials; you can have all the credentials in the world, and still make mistakes. Second:

Gliding is not flying. Active flight require very powerful chest muscles, which in turn require a massive breastbone. The Archaeopteryx just did not have those.

That was in response to your claim that it's "not a bird because it doesn't fly," based on the definition of "bird" as "animal which flies or has lost the ability to fly." That's an incorrect definition for many reasons, partly because "bird" is basically referring to "Archeopteryx and its descendants" and partly because "birds" are defined by their descent, which includes Archy, and also partly because flight had to start somewhere (with gliding)....but also because of the nature of Archy as a transitional form --- it has some traits of birds, but also some traits of theropods, and so is considered to be a candidate for transitional form between dinosaur and bird. It's not entirely a bird, obviously, because it's showing a transition between bird and dinosaur, so it has traits of both. Saying it's not a bird is like saying that an Australopithecus is "not a human;" it's not supposed to definitively represent what a bird is, but it has traits that link it to birds, and it's one of the earliest species to do so, and so it's suspected to be a sort of "missing link" between birds and dinosaurs. You're sort of missing the point if you think you're making one by saying Archy "isn't a bird," just because it glides. Birds evolved from creatures that flew; creatures that flew evolved from Archy; Archy evolved from early theropods; ergo, Archy is an early ancestor of birds, a "transitional form" between birds and dinosaurs.

["Melyssa K" Kennedy]

Okay, I think we need to end this. We clearly have gotten our information from different sources and can never come to an agreement. I'm done arguing this point with you. I don't have time to sift through every fact in every scientific journal article that I have read to show you that Archaeopteryx is not a true bird and that powered flight is one of the characteristics that defines what a bird is. My project stands for itself and contains all the sources I used to make it.

Yes, credentials do matter. They don't make someone right or wrong, but they do lend merit to the ability of the person to find the appropriate research materials to prove or support their point. I know I have that ability and have produced many projects over the years with sources that prove the point I'm making. I can't help it if your sources don't present the same information as mine.

[Static_Martyr]

Okay, I think we need to end this. We clearly have gotten our information from different sources and can never come to an agreement.

I'm not sure what you mean, I haven't seen you cite any sources. I just took your word for it.

I don't have time to sift through every fact in every scientific journal article that I have read to show you that Archaeopteryx is not a true bird and that powered flight is one of the characteristics that defines what a bird is.

Well, I DO have time to explain to you that Archy doesn't have to be a "true" bird in order to be a transitional form between birds and dinosaurs. Australopithecus isn't a human, but it's a transition between humans. And if powered flight makes something a bird, then penguins aren't birds, either.

I guess I just don't understand what point you're trying to make. You're saying, "Archy wasn't a bird because it hadn't yet evolved the traits that make birds, birds," and I'm saying, "it's a common ancestor of birds, because it has some traits that are unique to birds (traits which I've listed multiple times, specifically, and cited sources to back up what I said). It's as if I had said that Australopithecus was a common ancestor between humans and apes, and you said, "But Australopithecus isn't a human, because it doesn't have all of the traits that define humans as humans." I didn't say it did.

Yes, credentials do matter. They don't make someone right or wrong, but they do lend merit to the ability of the person to find the appropriate research materials to prove or support their point

Unfortunately for you, though, they don't make an adequate substitute for factual argument and proper sourcing.

I know I have that ability and have produced many projects over the years with sources that prove the point I'm making. I can't help it if your sources don't present the same information as mine.

It's not just one source. It's many sources. Peer-reviewed scientific journals, chronicled by sites like TalkOrigins (which is basically a library of biological journals, studies and essays; it's a good first resort if you're looking for anything biological).

If you're going to criticize my source, that's fair enough, but at least be specific about what you think it got wrong. Otherwise, you're just using it as an excuse to avoid being precise. Anyway, I'm not aware of anything I said which actually contradicts anything in your powerpoint project, so I'm not even really sure where you're claiming that "our sources differ." On what?

["Melyssa K" Kennedy]

My sources are contained in here. I'm pretty sure I posted the link to it and mentioned what it was earlier in the thread. http://melyssathepunkrocker.devianta...91590#/d4jour3

Penguins evolved from an ancestor that was capable of powered flight.