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Natural Science Forum / Biology / Paleontology / October 2005Alright. This is embarrassing but I need help big time. More bird evolution trouble.
I am in trouble with my paper, I kind of don't know where to go from here. Can anybody point me in the right direction? This is an eMail I wrote to my Bio professor this morning, it has alot of questions in it that need answering somehow: Mr. Irwin, I have been trudging along on this thing, it has come along pretty well, alot of good arguments and analysis of counterarguments. I have however come to a point where honestly my knowledge of the subject is exhausted: Basically it is an issue of classification at this point. The recent findings in China are my main points of evidence for the Theropodan ancestry of modern aves. The only thing is that I am not sure what the heck the things are at this point. I know one of the specimens, Microraptor I believe, is a Dromaeosaur. But the others I am not sure about. I guess I just assumed that they were all Dromaeosaurs and built alot of my arguments around that assumption. However as it turns out the dang things might be something completely different, therefore really messing things up. This is turning into more of a this this this this this this and this guy, all maniraptors but of different families can be the most recent ancestors of modern aves. Tah dah. You pick which one looks cooler and that's the one that was the alpha #1 branch off to aves. There is obviously a huge amount of convergent evolution involved, and the time-frames involved are just baffling. It is as if flight, or at least feathers, appeared, then dissapeared for MILLIONS of years, and then re-appeared again, then GOT LOST AGAIN, and then re-appeared in these small maniraptors. IS it possible that these little raptors, all of different families, can ALL be the first ancestors of modern aves? Wouldnt that mean that there would be a ton of different genera of birds, most of which could only be related to eachother because of the shared character of feathers? And then there is the issue of the ratites, what the HECK were those? Were they closer related to Therizinosaurs as opposed to the little arboreal birds, do they represent the medium between large down-insulated theropods and small arboreal feather-flappers? How can they, with the temporal issue still causing problems. It is a MESS. Therizinosaurs occured mostly in the late Triassic and early mid Jurassic, and as far as I know they have only been found with small tube-projections, and not really anything significant enough to even call insulation. Arboreal micro-maniraptors lived in the same time frame as well. And then Deinonychus, basically proving that dromaeosaurids are secondarily flightless...How can something as complex as a feather EVOLVE INTO BEING MORE THAN ONCE? Especially among not so related things over HUGE expanses of time, and also among EXTREMELY related things in the same FAMILY over a very short period of time? Has that ever been seen before, where something like an EYE was lost and then re-evolved and then lost, in DIFFERENT genera of related animals???? Sorry this is turning into a really long eMail. I guess I havnt kept on top of the research like I should have, and now I am scrambling for answers that I cannot find in discertations or books. Too bad Ostrom had to croak, I would very much like to talk to him about this. I think it is going to take more time to figure this stuff out, and to get a better understanding of both the classification systems and the time-frames involved. Much more time. It has come to the point where I feel that I am coming to the point where the professional research being done is kinda not that far ahead of me, and that even they do not have the answers to some of these questions, or perhaps I just don't know where to look? I am cutting an entire section that has flawed classification data and is completely biased in the direction of the Dromaeosaurid hypothesis of flight synthesis, which I am now thinking of scrapping completely and stepping back to a general maniraptoran synthesis of flight. I am also just scrapping some tables and cladograms that make no sense to me at this point. Basically it is not worth much scientifically but an interesting read at this point. Haha. Thanks alot And there is the eMail. I was actually asking my teacher for a one month extension on the due date, we have had a year and a half to work on this paper but I have not been as on top of it as I should have. Tee-hee. I am a dumb busy kid, what can I say. Any help at all would be great. Thanks > I am in trouble with my paper, I kind of don't know where to go from > here. Can anybody point me in the right direction? This is an eMail I [quoted text clipped - 71 lines] > > Any help at all would be great. You are making this way more complicated than it needs to be. Feathers evolved fairly close to the base of Maniraptora, or maybe a bit before. Flight probably evolved once, but it's unclear exactly where, or which theropods exactly are secondarily flightless. But let's not confuse flight with the clade that composes living birds. They could be the only surviving group of many flying and secondarily flithtless theropods. All modern birds have a single common, flying ancestor. There is some ambiguity about exact relationships among Maniraptora, but it's not nearly as great as you think. Modern birds are not descended from therizinosaurs, but from something in the neighborhood of dromaeosaurs or deinonychosaurs. The major ambiguity is just where troodonts fit. Read some of these: Prum, R. O. 2003. Dinosaurs take to the air. Nature 421:323-324. Pisani, D., A. M. Yates, M. C. Langer, and M. J. Benton. 2002. A genus-level supertree of the Dinosauria. Proc. R. Soc. Lond. B 269:915-921. and various papers in Gauthier, J., and L. F. Gall (eds.). 2001. New perspectives on the origin and early evolution of birds: Proceedings of the international symposium in honor of John H. Ostrom. Yale University Press, New Haven. >I am in trouble with my paper, I kind of don't know where to go from > here. Can anybody point me in the right direction? This is an eMail I [quoted text clipped - 73 lines] > > Thanks I think some genetic analysis of aves thrown at the issue is in order. >>I am in trouble with my paper, I kind of don't know where to go from >>here. Can anybody point me in the right direction? This is an eMail I [quoted text clipped - 75 lines] > > I think some genetic analysis of aves thrown at the issue is in order. Why? It would seem to be irrelevant, unless you can get some genes out of a variety of extinct theropods. So...... Does anybody know what's goin on enough to explain some of this stuff to me, I will look up the references, but there is only so much I can understand as there is much ambiguity and apparent subtelty involved in the matter... Thanks > So...... > > Does anybody know what's goin on enough to explain some of this stuff > to me, I will look up the references, but there is only so much I can > understand as there is much ambiguity and apparent subtelty involved in > the matter... You might also want to look at the May 2005 issue of Natural History. Nice popular article, with tree. OK. let me see if i can explain this OK since I'm in a hurray. No.1: Microraptor is a dromeosaur from the early cretaceous of china. There is no doubt on that. The amazing thing is that its has downy feathers. However it is also a Juvenal. No.2: As for Therizinosaurs there still is a lot of debate. there are presently two main theory's on there classification. One is that they are a sister group to oviraptorids. However the more widely excepted idea, proposed by sereno and currie is that they are closely related to ornothimimids. meaning they were not as closely related to birds. though more closely than say allosaurus or dilophosaurus. No.3: Birds are most closely related to ceolosaurs. of which at present there are five main branches. Dromeosaurs, tyrannosaurs, Oviraptorids, ornithomimids, and Therizinosaurids. The most closely related to birds are the dromeosaurs followed by the oviraptorids and tyrannosaurs. No.4: Maniraptorids are what paleontologists call a clad. they are animals that have similar characteristics. Though may be of different families,genera, etc. The main two things that make maniraptorids or at least what they were thought to be was the fracula or wishbone and the wrist bone. for a long time just included oviraptorids and dromeosaurs and of course birds. however new evidence has come to light some of which has yet to be published. close study of tyrannosaurs shows that there wrist bone and fraculas are very closely related to that of birds than to other dinosaurs so this has upset the status quo. So maniraptors are really just a group that have things similer to birds but does in no way mean there ancestors. No.5: And last but not least there evolutionary relationships. By no means are dromeosaurs and ovirators necessarily the direct ancesters of birds. especially since most of them come after the first bird appeared. they are animals with a common ancestor. As a good example is human evolution. neanderthals and modern humans have a common ancestor though the neanderthals are in no way our ancestor. the same thing here. Birds and dromeosaurs had a common ancestor and birds evolved one way and dromeosaurs the other. though because of the wonderful finds like microraptor we know they had a common ancestory and can guess what early bird ancestors were like. I hope this helps. If you need more help on this let me know. > > So...... > > [quoted text clipped - 5 lines] > You might also want to look at the May 2005 issue of Natural History. > Nice popular article, with tree. > OK. let me see if i can explain this OK since I'm in a hurray. > No.1: Microraptor is a dromeosaur from the early cretaceous of china. > There is no doubt on that. The amazing thing is that its has downy > feathers. However it is also a Juvenal. That may be true of the first specimen, the one that was part of "Archaeraptor". However, the two specimens of Microraptor gui are adults, and the cool thing about them is that they have four wings with well developed flight feathers. > No.2: As for Therizinosaurs there still is a lot of debate. there are > presently two main theory's on there classification. One is that they [quoted text clipped - 3 lines] > though more closely than say allosaurus or dilophosaurus. > No.3: Birds are most closely related to ceolosaurs. I think we can do better than that. They are coelurosaurs, but they are also maniraptorans, which narrows the field. > of which at present > there are five main branches. Dromeosaurs, tyrannosaurs, Oviraptorids, > ornithomimids, and Therizinosaurids. The most closely related to birds > are the dromeosaurs followed by the oviraptorids and tyrannosaurs. > No.4: Maniraptorids are what paleontologists call a clad. they are > animals that have similar characteristics. That's "clade", meaning that they include a common ancestor and *all* its descendants. Clades don't actually need to have similar characteristics. Archosauria, for example, is a clade that includes species as dissimilar as alligators and albatrosses. > Though may be of different > families,genera, etc. The main two things that make maniraptorids or at > least what they were thought to be was the fracula or wishbone and the > wrist bone. That's "furcula". But that's not a character of Maniraptora. It's found in many other theropods, for example Allosaurus. The wrist bone in question is better; it's called a semilunate carpal, and is a crucial character of Maniraptora. > for a long time just included oviraptorids and dromeosaurs > and of course birds. however new evidence has come to light some of [quoted text clipped - 3 lines] > maniraptors are really just a group that have things similer to birds > but does in no way mean there ancestors. No, but it does mean they are closely related by common descent from an ancestor possessing that trait. > No.5: And last but not least there evolutionary relationships. By no > means are dromeosaurs and ovirators necessarily the direct ancesters of > birds. In fact, as defined, they are clearly not. > especially since most of them come after the first bird > appeared. they are animals with a common ancestor. As a good example is [quoted text clipped - 16 lines] >>You might also want to look at the May 2005 issue of Natural History. >>Nice popular article, with tree. ok I will agree on a few thigs that you said though most of what I put down was rehash from currie when I talked to him last month. clade can also mean a veriety of things also not just a common ancestor. In fact the furcula has a lot to do with relationships the shape and fit has a lot to do with it. Though the semilunate carpal has a lot to do with it. And i do owe a bit of thanks for johns correction on the furcula. I never was good in anatomy. My masters thesis is evolutionary relationships. So i guess i better get that down. > > OK. let me see if i can explain this OK since I'm in a hurray. > > No.1: Microraptor is a dromeosaur from the early cretaceous of china. [quoted text clipped - 76 lines] > >>You might also want to look at the May 2005 issue of Natural History. > >>Nice popular article, with tree. > ok I will agree on a few thigs that you said though most of what I put > down was rehash from currie when I talked to him last month. clade can > also mean a veriety of things also not just a common ancestor. That's not true. "Clade" has one meaning only and I would be very surprised if you could find it used in any other way. There are several definitions but all are equivalent. A clade is not a common ancestor; it's a common ancestor and all its descendants. > In fact > the furcula has a lot to do with relationships the shape and fit has a > lot to do with it. If you mean that there are characters involving the shape of the furcula that diagnose Maniraptora, that might well be true. But mere possession of a furcula, as you seemed to be saying, is not such a character. > Though the semilunate carpal has a lot to do with > it. And i do owe a bit of thanks for johns correction on the furcula. I [quoted text clipped - 81 lines] >>>>You might also want to look at the May 2005 issue of Natural History. >>>>Nice popular article, with tree. yes the mere possession of a furcula does not a all mean a dinosaur is a maniraptor. The characteristics in the shape do help the diagnosis. The big gun though is the semilunate carpal. And as for the clade thing I guess I have to put this the right way A "clade" is a group of animals that have many things in common thus they would all have a common ancester. maniraptor really include most ceolosuars. though i think they all are minus one or two correct me if i'm wrong. however i used to think of the term Clade as you defined obove for years until james farlow used the term clade recently in his presentation at the tyrannosaur symposium. He used the term clade when he was comparing similarities in footprints. though many of the animals had nothing in common otherwise. Though I'm not totally agree with what he said i did find it interesting. His paper on this subject will be published next year in december. > yes the mere possession of a furcula does not a all mean a dinosaur is > a maniraptor. The characteristics in the shape do help the diagnosis. > The big gun though is the semilunate carpal. And as for the clade thing > I guess I have to put this the right way A "clade" is a group of > animals that have many things in common thus they would all have a > common ancester. This gets a bit philosophical, but you have the cart before the horse. A clade exists regardless of whether we can recognize it. We recognize clades by their similarities, though it's possible to recognize a clade even if no single character state is shared by all of them. And of course we can be wrong too. > maniraptor really include most ceolosuars. though i > think they all are minus one or two correct me if i'm wrong. I can't, because I don't know what you mean. There is more than one definiton of coelurosaur, whic creates confusion. However, by the definitions I know, compsognathids, tyrannoasurids, and ornithomimids are all coelurosaurs but not maniraptorans. (The last are maniraptoriforms but still not maniraptorans.) Your mileage may vary. > however i > used to think of the term Clade as you defined obove for years until [quoted text clipped - 4 lines] > find it interesting. His paper on this subject will be published next > year in december. Is it possible you were confused by what he said? I can envisage a tree of footprints on which there are "clades", i.e. just nodes on a tree. But they wouldn't be real clades, just "clades". That is, if a tree is not intended to represent phylogeny, it would contain no putative clades, but we might call nodes by that name in analogy to real clades. yes this is getting confusing because i'm lost with some of the things your saying. it is true that compsognathids, tyrannosaurids, and ornithomimids are ceolurosaurs but not maniraptorids. farlow refered to the fact that we must look at the fact there are at least two clades based on his study. one that is based on evolutionary relationships. As said before a common ancester and all its decendints. however the one things that most people had a hard time with was his second so called clade. A group of animals that may have a single triat in common but nothing lse. And i have his paper in my hand at the moment. i guess the clade has really to do with foot prints more than anything else. As he points out that emu, hadrosaur, and iguanodont footprints are almost identicle and that the foot structure is very similer. I guess you could say that they are not true clades. Though as i'm sure you know that hadrosaurs and emu have really nothing in common. by seeing that the emu and hadrosaur had such similar footprints must mean that there lower leg strcture was similar. thus you can use the living animal as a model for reconstructing the extinct. or at least there feet. I think what your refering to is evolutionary clades. His clades are ones that have one thing in common and have nothing else what he calls non evolutionary clades. beside the fact the archeologists use the term clade for people that have religeon or other things in common but many other differences. As an example the indians of the northern plains. As one thing that i would like to point out though that came up at the symposium was the fact that peter larson on his last T-rex dig found a semilunate carpal of a rex. And after carefull study found that it was almost ideticle to a dromeosaurs. so now there going to need to come up with more then the two reasons stated above on classifying a dinosaur as a maniraptorin. Either they include tyrannosaurids in maniraptorins which i'm not sure i totally go along with. or there must be more than just the furcula and the semilunate carpal similarities with birds that classifys a dinosaur as a maniraptorin. as with all of paleontology its always seems to change and it gets hard to keep up. > yes this is getting confusing because i'm lost with some of the things > your saying. it is true that compsognathids, tyrannosaurids, and [quoted text clipped - 16 lines] > have one thing in common and have nothing else what he calls non > evolutionary clades. Could you give a complete citation for that paper? If he's using "clade" in that sense, it's unique to him, and it's a very silly use of the term. > beside the fact the archeologists use the term > clade for people that have religeon or other things in common but many > other differences. Can you back up that usage with a quote from somewhere? > As an example the indians of the northern plains. As > one thing that i would like to point out though that came up at the [quoted text clipped - 7 lines] > classifys a dinosaur as a maniraptorin. as with all of paleontology its > always seems to change and it gets hard to keep up. There is some ambiguity about what "semilunate carpal" should mean. Holtz (in the Ostrom Symposium book) states it this way: a fusion of distal carpals I and II is a synapomorphy of Neotheropoda; adoption of a semilunate shape for this fused carpal is a synapomorphy of Tetanurae; and the expansion to cover metacarpals I and II is a synapomorphy of Maniraptora. Maniraptora is *defined* as all taxa more closely related to birds than to Ornithomimus. It is diagnosed by a variety of characters, which may change depending on author and details of the tree being proposed. i do not have the whole paper since is has yet to be finnished though i would like to have the whole thing. I think i have a few more papers than what i got next to me. If not i know the university has one so i can try to look it up tomorrow if i got the time. I doubt they would not have it. i have read the ostrum syposium bok so that is not new to me. larsonss main point was the fact besides the fitting and shape of the semilunate carpal {which i think is from wyrex}, the fact that the metatarsuls and tibia and fibia in relation to the other bones { sorry to make this so brief i got class in about 15 minutes] was in his opinoin more like that of oviraptor than that of the ornithomimids. meaning that they are really more closely related to the maniraptorids {or as he seemed to be hinting a part of the group which seems to be a long shot in my mind} . Currie when he decribed the maniratorids as being mostly small agile creature minus utah and megaraptor. So if tyrannosaurs were more closely related to the oviraptorids should they be considered maniraptorids as well was the toss up question. my personal opinion is no. |
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