This site presents the idea that birds developed from flying pterosaurs.
This is a credible alternative to the current, mainstream idea that birds developed from land-based dinosaurs.
Wednesday, October 27, 2010
Questions
If anyone has questions, comments or objections, feel free to post them. I will do my best to answer them
Why do birds share the following features with dinosaurs? Why aren't they present in pterosaurs?
Ectopterygoid lateral to transverse flange of pterygoid; postfrontal absent; temporal muscles extend anteriorly onto skull roof; quadrate head laterally exposed; S-shaped neck; dorsal vertebrae shorter; at least 3 fully incorporated sacral vertebrae (with 3rd incorporated from dorsal vertebrae); forelimb < 50% length of rear (reversals in several groups); deltopectoral crest extends further down humerus; humerus with elongate deltopectoral crest; manus 4 with <4 phalanges; claws on 1-3 only; semi-perforate (usually fully perforated) acetabulum with buttress; brevis shelf on ilium; ischium with obturator process restricted to anterior 1/3rd; femur with ball-like head; medial tuberosity of femur reduced; shaft of femur straight or bowed anteriorly; femur vertical; femur has greater, lesser & 4th trochanters; tibia with cnemial crest; well-developed ascending process of astragalus on anterior face of tibia; calcaneum with concave surface for articulation of fibula; metatarsals elongate and function as part of pes
Why do birds share the following features with theropods? (note that pneumatisation is present in many theropods, including ones you don't think are anything to do with birds). Why aren't they present in pterosaurs?
Skull pneumatized; nares formed by premaxilla & nasals, excluding maxilla; nasal cavities communicate laterally to large diverticula at antorbital fossa; promaxillary fenestra usually present at anteroventral apex of the antorbital fossa; $ lacrimal extends to top of skull; horns & crests (display?) common; nasals usually unsutured at midline; other diverticula invade palate & peri-orbital bones (antorbital diverticula increase in advanced species.); trend to more anterior-facing orbits and increased brain size; opisthotic and exoccipitals always fused; $ intramandibular joint present; external mandibular fenestra present; posterior end of angular usually anterior to articular; long palatine-maxilla suture; some have diverticula from throat through middle ear to braincase; angular with anterior hook; teeth usually laterally compressed, curved, with 2 serrated edges; normally 23 pre-sacral vertebrae; prominent prong-shaped cervical vertebral epipophyses (lost in some advanced species.); long caudal prezygapophyses; limb bones extensively pneumatized, as are ribs & vertebrae; diverticula may communicate with lungs; strap-like scapula; humerus <50% of femur; metacarpals I-III dorsally pitted (ligament attachments); phalanges of hand elongate; loss or reduction of manus 4 & 5; $ claws, especially on manus, long curved & sharp; ilia large and blade-like; expanded distal end of pubes ("pubic boot"); astragalus tends to enlarge, calcaneum to be reduced lost; astragalus with pronounced ascending process; metatarsals tend to increase in size relative to femur; pes 1 tends to develop large "raptor" claw; metatarsals II & IV come in contact & metatarsal III reduced (shock-absorbing arctometatarsalia)
And why do they share the following features with all coelurosaurians? Why aren't they present in pterosaurs?
Nasals do not participate in antorbital fossa; expanded, circular orbit; jugals reach antorbital fenestrae; Fenestra in roof of mouth; <16 caudals have transverse processes; "boat-shaped" chevrons; fused sternal plates; "cranial notch" between scapula & coracoid absent; coracoid with well-developed posterior projection; elongated forelimbs, especially manus; semilunate carpal in wrist; metacarpal I reduced; long, thin metacarpal III ; $ ischium reduced to <2/3 length of pubis; loss of ischial foot; triangular obturator process on ischium; generally femur substantially shorter than epipodialia; $ ascending process of astragalus >25% length of tibia; knee and ankle hinge-like; fibula reduced and immobile in relation to tibia; tarsal bones elongated; metatarsal III pinched between II & IV (arctometatarsalian condition or similar)
And why do pterosaurs have the following characters that, bar two or three aren't present in birds?
Large eyes; sizeable brains; hollow long bones; sternum (but small or no ossified keel); long retroverted scapula as in birds; ventral edge of coracoid articulates with sternum as in birds and supports pectoral girdle; expanded sternum with keel; humerus longer than sternum; big deltopectoral crest on proximal. humerus for flight stroke muscles; primitively, deltopectoral crest has straight edges; forearm longer than humerus; pteroid bone in wrist; hand with elongate digit 4 supporting wing membrane; manus 1-3 retained, with unguals, and at least sometimes robust; wing membranes with fibers for stiffening; short pubis with pre-pubic bones; highly mobile hip joint; femur bowed and shorter than tibia; fibula reduced and fused to tibia; mesotarsal ankle; 4 elongated, closely appressed metatarsals plus reduced 5th; pes with 5 digits; pes 5 small & without claws; longish penultimate phalanges on feet (not digitigrade?); wing membrane extends to leg in some or all groups, even between rear legs (uropatagium); pteroid supports additional membrane to neck; fibers in membrane; typical gait may have been quadrupedal and plantigrade, with limbs at least partly sprawling; bones generally highly pnematic or hollow & supported by internal struts; integument possibly with hair-like pilosity.
Note here that the ones that they do share with birds can generally be seen to be convergent- the pterosaur sternum is made of different bones to the bird one. (It includes the clavicles for instance).
To make this manageable I will refer to the top post as (A), the one below it as (B), the one below it as (C), and the lowest one (immediately above) as (D). The other thing we need to be clear about is distinguishing between maniraptors and non-maniraptor theropods. We cannot use the label "dinosaur" because that will be confusing.
So my questions to you, to begin with: In (A) by "dinosaur" do you mean non-maniraptor theropods? In (B) by "theropod" do you mean non-maniraptor theropods? In (C) by "coelurosaurians" do you mean non-maniraptor coelurosaurians?
Also we need to agree on what "bird" means. Does "bird" mean? All maniraptors? Avialae? Aves? Neornithines? Something else?
Also it will be helpful to me if you give me the link where I can see the source of the characteristics you have listed in (A), (B), (C) and (D).
Ground rules: I do not allow swearing or personal insults on this site.
No. A is all dinosaurs, saurischians and ornithischians. B is all theropods including maniraptorans. C is all coelurosaurians including maniraptorans. I'd refer to bird as Avialae in that list. But I'd prefer not to use the name for clarity I think.
The problem with not distinguishing between maniraptors and non-maniraptors dinosaurs (theropods, coelurosians) is that the maniraptors are birds and the non-maniraptors are dinosaurs. So if we do not make that distinction we are mixing dinosaurs and birds together. So, if for example you list a characteristic that you believe is found in "dinosaurs" it may be the case that it is only found in the maniraptors (and not in the non-maniraptors) and therefore supports the pterosaur to bird theory but not the dino to bird theory. There are posts on the site that go into this topic at length.
I am quite willing to take bird" as aviale when you use it. Each time I want to refer to "bird" I will follow it with the name (maniraptor) since all creatures currently labeled as maniraptors are birds. If I wish to distinguish bird groups within "maniraptor" I will refer to the specific group name.
Thanks for the link. Palaeos.com is a fairly large site. Could you please give me the specific page address. That would be great.
While I await your response to my comment that we need to distinguish between maniraptors and non-maniraptor dinosaurs, I will respond to comment (D).
You have said: "And why do pterosaurs have the following characters that, bar two or three aren't present in birds?"
By "bird" you mean "avialae". For the purposes of this question that is still not precise enough because it includes both primitive birds such as enantiornithes and modern birds. And as you know the pterosaur to bird theory proposes that pterosaurs evolved into primitive birds and those primitive birds evolved into modern birds. As a general answer to your question, I would say that if any characteristic is found in a pterosaur but is not found in modern birds, then that characteristic was modified or lost in the progression from pterosaur to primitive bird to modern bird. For example, the pteroid evolved into the alula so that charateritic is found in modern birds. The long 5th digit of the pterosaur (which your source incorrectly called the 4th) shortened in the evolution from pterosaur to primitive bird. Etc.
In Comment (A) you posted: "Why do birds share the following features with dinosaurs? Why aren't they present in pterosaurs?"
I will begin with the question "Why aren't they present in pterosaurs"?
If any characteristic is found in a modern bird but is not found in any pterosaur, then that characteristic evolved in the progression from pterosaur to primitive bird to modern bird. This is standard evolution.
Concerning the non-maniraptor dinosaurs - if any characteristic is found in a modern bird and also found in a non-maniraptor dinosaur it is convergent evolution. But please provide evidence that any of the characteristics you listed are indeed in non-maniraptor dinosaurs and also in modern birds.
In Comment (B) you posted: "Why do birds share the following features with theropods? (note that pneumatisation is present in many theropods, including ones you don't think are anything to do with birds). Why aren't they present in pterosaurs?"
I will begin with the question "Why aren't they present in pterosaurs"?
If any characteristic is found in a modern bird but is not found in any pterosaur, then that characteristic evolved in the progression from pterosaur to primitive bird to modern bird. This is standard evolution.
Concerning the non-maniraptor theropods - if any characteristic is found in a modern bird and also found in a non-maniraptor theropod it is convergent evolution. But please provide evidence that any of the characteristics you listed are indeed in non-maniraptor theropods and also in modern birds.
In Comment (C) you posted: "And why do they share the following features with all coelurosaurians? Why aren't they present in pterosaurs?"
I will begin with the question "Why aren't they present in pterosaurs"?
If any characteristic is found in a modern bird but is not found in any pterosaur, then that characteristic evolved in the progression from pterosaur to primitive bird to modern bird. This is standard evolution.
Concerning the non-maniraptor coelurosaurians - if any characteristic is found in a modern bird and also found in a non-maniraptor coelurosaurian it is convergent evolution. But please provide evidence that any of the characteristics you listed are indeed in non-maniraptor coelurosaurians and also in modern birds.
If you're just going to include maniraptorans in avialae then just use "maniraptorans", because I want to keep "Avialae" to discuss the conventional meaning- Modern Birds (as conventionally defined) plus Archaeopteryx and all the species in between. Avialae is characterised by a series of features that are not present in any other maniraptorans
So each of those characters in each of those posts is convergent evolution? Because they aren't found in pterosaurs, but they are found in maniraptorans (Avialae, Deinonychosauria, Oviraptorosauria, etc). But those characteristics are found in virtually all dinosaurs/theropods/coelurosaurians (depending on the post we're looking at.) They're how we recognise Ovirpator, for example, as being a coelurosaurian/theropod/dinosaur, and not a pterosaur. It has the characters used to define coelurosaurians. It does not have the characters used to recognise pterosaurs. Do you not see why the fact that because this list is so long, and the list linking pterosaurs and birds (hollow bones and your misidentified fingers) is so short should tell you something?
Start with Dinosauria, and work your way down the cladogram to birds. They list references in the diagnosis, which you can trace back to the original papers.
You said: "If you're just going to include maniraptorans in avialae..." I did not say that. Avialae is included in maniraptora. I am willing to use "avialae" when appropriate.
You said: "But those characteristics are found in virtually all dinosaurs/theropods/coelurosaurians (depending on the post we're looking at."
You are claiming that the listed characteristics are found in both maniraptors and non-maniraptor coelurosaurians. Please provide evidence for that assertion with reference links. And also show that they are characteristics unique to non-maniraptor coelurosaurians and not just general archosaur traits. Note: The dino to bird theory claims that birds evolved from non-maniraptor coelurosaurians.
Concerning the length of the lists. I just gave two examples of traits that relate pterosaurs to modern birds. This site has dozens and dozens. Have you read the entries on this site?
As a general point I am not interested in investigating a whole bunch of dinosaur characteristics. Those who propose the dino to bird theory can do that. I am interested in the links between pterosaurs and primitive birds and the links between primitive birds and modern birds. And in fact this site gives dozens and dozens of those. Concerning the lists that Dave Godfrey gave, what interests me is how those traits relate to pterosaurs and birds. And I will post on that. Some (possibly most) have already been covered on the site already.
The traits I have listed are diagnostic characters for the three dinosaurian clades. Your reference is Palaeos. Read it. Move through the cladogram, clicking the links. It references its claims in the scientific literature. You can find links to the full references there. You may even find you can get access to the original paper.
You have lots of assertions about how dromaeosaurs and birds have similar characters. But nowhere have you managed to link these to the pterosaurs. You state thaty pterosaurs have the same shoulder articulation as enantiornithines, but the part you quote says that... "The coracoid shows a well developed biceps tubercle but lacks a deep coracoidal flange as reported for Changchengopterus" But the biceps tubercle isn't the same as the scapular-coracoidal joint. This is not a character that links birds and pterosaurs. Its two different characters.
All the other characters can similarly be dismissed as convergences- it is not surprising that pterosaurs and birds have large brains given over to processing complex information.
Pterosaurs retain the diapsid skull condition, which birds have lost, although Confusciusornis retains it. This is a primitive character that is also present in crocs. It will not help you.
Birds have a mandibular fenestrae. Pterosaurs do not. Other archosaurs (apart from pterosaurs) all have this too. Why has this been lost, and then re-acquired if pterosaurs are ancestral to birds?
Beaks have evolved multiple times. Turtles have them. Ornithischians have them. Limusaurus (a ceratosaur) has one. Birds have one. A whole series of other diapsids that have nothing to do with archosaurs have them. Such a widely dispersed character is not helpful.
You have said: "You have lots of assertions about how dromaeosaurs and birds have similar characters. But nowhere have you managed to link these to the pterosaurs."
I invite you to read this site. It shows the links - dozens and dozens of them. With specific supporting references.
You have said: "All the other characters can similarly be dismissed as convergences- it is not surprising that pterosaurs and birds have large brains given over to processing complex information."
If all the dozens and dozens of characters that link pterosaurs to birds, that I have posted about, are convergences that can be dismissed as convergences, then whatever traits that you claim link non-maniraptor coelurosaurians to maniraptors can similarly be dismissed as convergences. I am not investigating the dinosaur characteristics for you. If you wish to propose the dino to bird theory then you can present your case.
I will be analyzing the traits you listed from the pterosaur to bird perspective.
You have said: "Beaks have evolved multiple times. Turtles have them. Ornithischians have them. Limusaurus (a ceratosaur) has one. Birds have one. A whole series of other diapsids that have nothing to do with archosaurs have them. Such a widely dispersed character is not helpful."
Are there any non-maniraptor coelurosaurians with beaks? For example, any Compsognathids or Tyrannosaurs with beaks?
You have said: "Pterosaurs retain the diapsid skull condition, which birds have lost, although Confusciusornis retains it. This is a primitive character that is also present in crocs. It will not help you. Birds have a mandibular fenestrae. Pterosaurs do not. Other archosaurs (apart from pterosaurs) all have this too. Why has this been lost, and then re-acquired if pterosaurs are ancestral to birds?"
I covered these topics here: http://pterosaurnet.blogspot.com/2010/05/skull.html May I suggest you read it and post any questions there, about what I have said?
You don't mention whether birds have a mandibular fenestrae (they do). You don't mention anything about the pterosaurian postorbital bone. Its not covered there. I read the post. I'm not posting there, because it'll be a pain to find your replies on a post 6 months old. I'd rather keep this conversation here. (To be perfectly honest I'd rather have the conversation at TR).
I am not aware of any non-maniraptoran coelurosaur with a beak. But as I pointed out, lots of sauropsids that aren't anything to do with birds have beaks. Its such a widely distributed feature that you can't link its presence in some pterosaurs and its presence in some maniraptorans as being significant.
None of the "dozens of characters you list" are useful. I looked at some above they are not helpful in determining ancestry. They're either not even the same character (the pterosaur shoulder) not homologous (bird and pterosaur crests) too widely distributed among other taxa (beaks), primitive to all archosaurs (through-flow lungs), errors on the websites you quote (feathers are analogous to the thermoregulatory function of pycnofibrils not the wing supporting function of the actinofibrils- the two "fibrils" are very different in composition and structure) and in some cases characters which define maniraptorans (the semi-lunate carpal), but which you don't provide any information about whether they're present in pterosaurs.
So, why are there vastly more characters that unite birds and dinosaurs that aren't clearly adaptations to flight and weight loss, than unite pterosaurs and birds? Your theory is not parsimonious.
You have said: "You state thaty pterosaurs have the same shoulder articulation as enantiornithines, but the part you quote says that... "The coracoid shows a well developed biceps tubercle but lacks a deep coracoidal flange as reported for Changchengopterus"
Can you give the link for this please? I do not remember ever saying that "pterosaurs have the same shoulder articulation as enantiornithines,"
I've just noticed your posts on bird and pterosaur wrists. You state that-
"The wing of a modern bird, for example, has only two remaining carpals; the radiale (the scaphoid of mammals) and a bone formed from the fusion of four of the distal carpals."
The bird has a radiale, and ulnare (which are not made of other fused bones) and four distal carpals fused to the metacarpals to form a carpometacarpus.
This is not the same as that seen in pterosaurs. They have three carpals, a distal syncarpal (made of fused bones) and proximal syncarpal (made of fused bones) a medial carpal, and the pteroid (possibly- but there is certainly no indication that it is the thumb anywhere in the peer-reviewed literature). So again the two conditions are not homologous. You need to unfuse the proximal syncarpal to form the radiale and ulnare of birds, fuse the medial carpal and the distal syncarpal to the metcarpals of the hand to form the carpometacarpus. And you need to do even more unfusing to get to the condition in the non-avian maniraptorans.
And if you want the pteroid to be the thumb you have to completely re-evolve the metacarpals, phalanges and claws that are present in maniraptorans.
"Specifically, in Enantiornithes, the scapular facet of the coracoid is a convex knob [tubercle] and the coracoidal facet of the scapula is a concave dish-shaped excavation to receive it. In neornithes the scapular facet of the coracoid is a round pit, which receives the coracoidal tubercle of the scapula"
Then you quote Xiaolin Wang's description of Wukongopterus
"The coracoid shows a well developed biceps tubercle but lacks a deep coracoidal flange as reported for Changchengopterus"
And you say.
"The pterosaur scapula/coracoid relationship (articulation) is the same as that of the enantiornithes."
The articulation is not the same. The two tubercles are completely different structures.
You have said that you are "not aware of any non-maniraptoran coelurosaur with a beak."
You specifically raised the topic of beaks. Pterosaurs have beaks. Non-maniraptoran coelurosaurs do not have beaks. The dino to bird theory is based on the idea that birds evolved from non-maniraptoran coelurosaurs.
On the one definite trait that we have looked at so far and agreed on, the pterosaur to bird theory has been supported and the dino to bird theory has not been supported.
You have said: "So, why are there vastly more characters that unite birds and dinosaurs that aren't clearly adaptations to flight and weight loss, than unite pterosaurs and birds? Your theory is not parsimonious."
Can you support that assertion please? To this point you have not done so. In fact in the one trait that we have agreed on so far, your statement is not correct.
Also you say "that aren't clearly adaptations to flight and weight loss," as if we can simply overlook those characteristics.
Consider this: One airplane is closer to another airplane than either is to a bicycle and a lot of that is that both planes are able to fly. They have a huge number of characteristics related to the fact that they both can fly. Do we overlook those aspects of them, that give them the ability to fly? You must be joking.
You have said: "None of the "dozens of characters you list" are useful. I looked at some above they are not helpful in determining ancestry. They're either not even the same character (the pterosaur shoulder) not homologous (bird and pterosaur crests) too widely distributed among other taxa (beaks), primitive to all archosaurs (through-flow lungs), errors on the websites you quote (feathers are analogous to the thermoregulatory function of pycnofibrils not the wing supporting function of the actinofibrils- the two "fibrils" are very different in composition and structure) and in some cases characters which define maniraptorans (the semi-lunate carpal), but which you don't provide any information about whether they're present in pterosaurs."
This is an odd statement: "primitive to all archosaurs (through-flow lungs)", May I suggest you research the subject of flow-through lungs and archosaurs. Your statement is completely incorrect. I have also covered that subject at length on the site.
May I suggest that you actually read the entries on this site. I am not going to spoon feed you by repeatting one point at a time what I have already covered on the site.
Beaks evolved more than once in the pterosauria. Not all pterosaurs have them. Some have beaks and teeth. Some beaks and no teeth. Some teeth and no beaks. Pteranodon and Nyctosaurus have beaks. The various Azdarchoids have beaks. But the pteranodontians aren't Azdarchoids, they're Ornithocheiroids. Most of which have lots of teeth. So this character doesn't help you even if we only look at pterosaurs.
But it gets worse for you. Not all of the avialae had beaks. For example, Archaeopteryx didn't. Not all non-avian maniraptorans had beaks dromaeosaurs and troodontids didn't. Nor did the primitive oviraptorans (Incisivosaurus had very obvious teeth.)
Limusaurus is a non-coelurosaurian theropod. It has a beak. Coelurosaurians share a common ancestor with non-coelurosaurian theropods. And share closer ancestry with some non-coelurosaurian theropods than others. So we have a non-maniraptoran, non-coelurosaurian theropod with a beak. And then we have all the ornithischians with beaks. And then all the things outside archosauria with beaks.#
Its a very common feature. Its evolved many times in many lineages that neither of us think are closely related to birds. It is therefore not helpful to your argument. As its not a character I propose that unites birds and any dinosaurs (because it evolves independently multiple times) it harms your argument not mine.
Your comments about fingers and carpals are completely wrong. I have covered that at great length. The pteroid bone is the first finger. From that everything else follows smoothly. It is a vastly interesting subject but I am not going over it all again just for you. Read the entries.
Alligators have through-flow lungs. There was a paper on it last year. It was discussed in one of your threads on TR. It got its own thread. My statement is in fact completely correct.
Oh, and you know how aeroplanes don't breed? Its why its a terrible analogy for producing cladograms. But you shouldn't forget the Gossamer Albatross a human powered aeroplane built around a bicycle. You're also totally ignoring the massive differences in how birds and pterosaurs build their wings. Not to mention all the non-flight related things that are totally different. If there was a pattern of relatedness shouldn't they be similar? And yet they're not. And nor, when we look at them, are the details of their wings.
You have posted a comment that begins with: "Beaks evolved more than once in the pterosauria. Not all pterosaurs have them......"
This is where the discussion becomes a lot less interesting and a lot less fun for me - when you begin to work up elaborate stories to try cover over a fact that goes against what you are proposing and supports strongly what I am saying. And not surprising you fall back on the convenient, convergent evolution non-explanation. Do you think that anybody will think that the fact that pterosaurs have beaks like birds and that the dinosaurs you claim evolved into birds do not, is good for your point of view. I am not using up my time responding to every just-so story you come up with.
I'm quoting from what you've written about carpals. I read the entries. Both of them. You made a mistake. You're being called on it. Bird and pterosaurs wrists are different. Your quotes show it.
"Do you think that anybody will think that the fact that pterosaurs have beaks like birds and that the dinosaurs you claim evolved into birds do not, is good for your point of view."
I think people will read what I wrote and draw their own conclusions. Beaks are widely distributed among animals that neither of us think are anything to do with direct ancestry of either pterosaurs or birds. That has to be convergence. So when we see multiple origins of beaks in pterosaurs AND maniraptoriformes (Ornithomimids had beaks- are you including them in the "maniraptorans" that belong in pterosaurs or not? I forget. And Incisivosaurus has teeth and no beak, but its an oviraptoran- you even have a picture of it- so that's another independent origin for a beak), why is convergence suddenly forbidden as an explanation?
"Specifically, in Enantiornithes, the scapular facet of the coracoid is a convex knob [tubercle] and the coracoidal facet of the scapula is a concave dish-shaped excavation to receive it. In neornithes the scapular facet of the coracoid is a round pit, which receives the coracoidal tubercle of the scapula"
Then you quote Xiaolin Wang's description of Wukongopterus
"The coracoid shows a well developed biceps tubercle but lacks a deep coracoidal flange as reported for Changchengopterus"
And you say.
"The pterosaur scapula/coracoid relationship (articulation) is the same as that of the enantiornithes."
The articulation is not the same. The two tubercles are completely different structures.
Can you please support your assertion that: "The two tubercles are completely different structures."
You have a comment that begins with: "Alligators have through-flow lungs"
Are you claiming that birds evolved from alligators? No you are not. The question is - did compsognathids or tyrannosaurs have flow through lungs? Remember those are the groups the dino to bird theory claim evolved into birds. Modern birds have flow through lungs. Pterosaurs had flow-through lungs. The groups you claim evolved into birds did not have flow through lungs.
This is another situation like the beaks. Pterosaurs had the trait that birds have. Non-maniraptor coelurosaurians did not.
Now I will hear all the stories and spin about those facts. But the facts do not change.
On the two traits that we have talked about and agreed on the facts about, the pterosaur theory has been supported and not the dino to bird theory.
You posted: "(Ornithomimids had beaks- are you including them in the "maniraptorans" that belong in pterosaurs or not?"
Yes, I have included maniraptoriformes in the bird group that evolved from pterosaurs. I mention this on the site. It really would be good if you read the entries on this site. Instead of just shooting from the hip.
You posted: "And Incisivosaurus has teeth and no beak, but its an oviraptoran- you even have a picture of it- so that's another independent origin for a beak),"
Perhaps it is getting late, but how can the fact that Incisivosaurus has no beak be an example of independent origin of a beak?
You have said: "I'm quoting from what you've written about carpals. I read the entries. Both of them. You made a mistake. You're being called on it. Bird and pterosaurs wrists are different. Your quotes show it."
Is your argument that the pteroid is not the thumb? Or is there more to it than that? (I may have been unclear before and called it the first finger. I should call it the thumb for clarity).
You posted: "You're also totally ignoring the massive differences in how birds and pterosaurs build their wings."
Actualy I have studied at length the way pterosaur wings are built. Recent research ahs shown them to very complicated structures. And although I have not posted on this topic it is fascinating to see that the counterparts to the feather structures are already in prototpye version in the pterosur wing. And recently they have even found protofeather material on the pterosaur wing.
The main changes required are to shorten the 5th finger, fuse the non-pteroid fingers into the bird form, lose the webbing material and elaborate the actinofibrils into feather structures. There is more, but that is the heart of it. It really is quite interesting.
I will address some items in Comment (D): "And why do pterosaurs have the following characters that, bar two or three aren't present in birds? Large eyes; sizeable brains; hollow long bones; sternum (but small or no ossified keel); long retroverted scapula as in birds; ventral edge of coracoid articulates with sternum as in birds and supports pectoral girdle; expanded sternum with keel; humerus longer than sternum; big deltopectoral crest on proximal. humerus for flight stroke muscles; primitively, deltopectoral crest has straight edges; forearm longer than humerus; pteroid bone in wrist; hand with elongate digit 4 supporting wing membrane; manus 1-3 retained, with unguals, and at least sometimes robust; wing membranes with fibers for stiffening; short pubis with pre-pubic bones; highly mobile hip joint; femur bowed and shorter than tibia; fibula reduced and fused to tibia; mesotarsal ankle; 4 elongated, closely appressed metatarsals plus reduced 5th; pes with 5 digits; pes 5 small & without claws; longish penultimate phalanges on feet (not digitigrade?); wing membrane extends to leg in some or all groups, even between rear legs (uropatagium); pteroid supports additional membrane to neck; fibers in membrane; typical gait may have been quadrupedal and plantigrade, with limbs at least partly sprawling; bones generally highly pnematic or hollow & supported by internal struts; integument possibly with hair-like pilosity."
Here is an analysis of some of the items in the list: Birds have "sizeable brains" - like pterosaurs Birds have "hollow long bones" - like pterosaurs Birds have "expanded sternum with keel" - like pterosaurs As the list itself says, "pterosaurs have long retroverted scapula as in birds". Pterosaurs have "hand with elongate digit 4 [actually it is digit 5] supporting wing membrane". The elongate 5th digit shortened in the evolution to primitive bird. Pterosaurs had "wing membranes with fibers for stiffening". Those evolved into feathers. Pterosaurs have "wing membrane extends to leg in some or all groups, even between rear legs (uropatagium)". The membrane was lost with the evolution of feathers. The pterosaur's "pteroid supports additional membrane to neck". In the evolution to bird, the pteroid became the alula and the membrane was lost. Birds have "bones generally highly pnematic or hollow & supported by internal struts" - like pterosaurs It is said of pterosaurs that they have "integument possibly with hair-like pilosity." These are protofeathers.
Concerning Comment(D), I missed this obvious one directly from the list: "ventral edge of coracoid articulates with sternum as in birds and supports pectoral girdle".
I was thinking about the traits listed in Comment (D). Something seemed wrong about it. Then I realized that it did not include a great number of traits and aspects of pterosaurs. Here is some additional info that brings to light the enormous similarity of birds to pterosaurs, in addition to what I have said above.
http://en.wikipedia.org/wiki/Pterosaur
"Pterosaur bones were hollow and air filled, like the bones of birds. They had a keeled breastbone that was developed for the attachment of flight muscles and an enlarged brain that shows specialised features associated with flight.[4] In some later pterosaurs, the backbone over the shoulders fused into a structure known as a notarium, which served to stiffen the torso during flight, and provide a stable support for the scapula (shoulder blade).
As evidenced by hollow cavities in the wing bones of larger species and soft tissue preserved in at least one specimen, some pterosaurs extended their system of respiratory air sacs into the wing membrane itself.
Most pterosaur skulls had elongated, beak-like jaws. Some advanced forms were toothless (such as the pteranodonts and azhdarchids, though most sported a full complement of needle-like teeth
Unlike most archosaurs, which have several openings in the skull in front of the eyes, in pterodactyloid pterosaurs the antorbital opening and the nasal opening was merged into a single large opening, called the nasoantorbial fenestra. This likely evolved as a weight-saving feature to lighten the skull for flight
Pterosaurs are well known for their often elaborate crests.
The presence of pycnofibres (and the demands of flight) imply that pterosaurs were endothermic (warm-blooded).
The mechanics of pterosaur flight are not completely understood or modeled at this time[22][23], but it is almost certain that this group of animals was capable of powered flight in at least as wide a range of conditions as modern birds.
The wings were probably flapped in a manner grossly similar to that seen in birds (a group which displays many different flapping strategies among and within different species and different situations).
A 2009 study showed that pterosaurs had a lung-air sac system and a precisely controlled skeletal breathing pump, which supports a flow-through pulmonary ventilation model in pterosaurs, "analogous" to that of birds. The presence of a subcutaneous air sac system in at least some pterodactyloids would have further reduced the density of the living animal
The pterosaurs' flocculi occupied 7.5% of the animals' total brain mass, more than in any other vertebrate. Birds have unusually large flocculi compared with other animals, but these only occupy between 1 and 2% of total brain mass
Pterosaur's hip sockets are oriented facing slightly upwards, and the head of the femur (thigh bone) is only moderately inward facing, suggesting that pterosaurs had a semi-erect stance.
Pteranodon had slightly larger feet (47% the length of the tibia), while filter-feeding pterosaurs like the ctenochasmatoids had very large feet (69% of tibial length in Pterodactylus, 84% in Pterodaustro), adapted to walking in soft muddy soil, similar to modern wading birds
It is not known whether pterosaurs practiced any form of parental care, but their ability to fly as soon as they emerged from the egg and the numerous flaplings found in environments far from nests and alongside adults has led most researchers, including Christopher Bennett and David Unwin, to conclude that the young were only dependent on their parents for a very short period of time, while the wings grew long enough to fly, and left the nest to fend for themselves within days of hatching."
1. The bird crests you discuss are made of feathers. Pterosaur crests are made of bone with a horny coating. If you want a structure to which they are homologous you would do better to look at cow or Triceratops horns. At least they're made of the same material. But not all pterosaurs have crests. Not all birds have crests either. And lots of dinosaurs have crests too. So this feature is not helpful too you. Like beaks it is too widely dispersed to tell you enough.
2. Not all Avialans have beaks. Archaeopteryx does not have one. Not all pterosaurs have beaks. Incisivorosaurus is important because most oviraptorans have beaks, but it is a very primitive one. And does not have a beak. So beaks have evolved independently in Oviraptorans, because the most primitive member lacks one, but later ones have them.
3. Your reference for the Coracoidal Tubercule is Wikipedia.
"The coracoid tubercle is a prominent area on the anterior surface of the coracoid, just ventral to the shoulder socket (glenoid). The coaracoid tubercle forms the pointed portion in those coracoids described as "flexed". It was previously called the biceps tubercle because it was thought to be the origin of the M.biceps muscle. Makovicky & Sues (1998) followed Alick Walker (1990) in asserting that it is, instead, probably the origin of the M. coracobrachialis muscle."
It is not the same structure as the tubercle that forms the shoulder joint in the enantiornithines.
4. Actinofibrils are most probably made of collagen, a common protein used in supporting tissues. Pycnofibrils are most probably made of keratin, a structure found in the skin., but not within other tissues. Actinofibrils cannot therefore be ancestral to feathers. They are made of different proteins doing different roles.
5. Birds have smaller flocculi than pterosaurs. Why? Birds have an erect gait. Pterosaurs do not. But dinosaurs are pretty much unique among archosaurs in having an erect gait. So its more parsimonious to believe that this is not convergent.
6. Birds have through-flow lungs. Alligators have through-flow lungs. Sauropods have through-flow lungs. Maniraptorans have through-flow lungs. Theropods have through-flow lungs. All of these preserve either evidence of air sacs or have experimental data to back up these conclusions. Ornithischians probably had through-flow lungs, but their bones weren't permeated by air sacs. This is therefore almost certainly a basal feature present in all archosaurs.
7. That list of pterosaur characters includes several that you claim aren't mentioned. (Like their semi-erect gait). Or are only present in a few taxa and are therefore not characteristic of pterosaurs as a whole, but only a few species or specific groups (the nasoaneorbital fenestrae is a diagnostic character of pterodactyloids. Not Pterosauria as a whole. Which is what that list is about). Or are most likely present in all archosaurs. (The "lung-air sac system" you mention.
8 What is your peer-reviewed reference that pterosaurs have retained digit 1 as the pteroid bone? It is not quoted anywhere. You state that everyone's made this mistake many times, but you never actually provide any anatomical reason why we should agree with your diagnosis. What specimens have you studied that allow you to make this judgement?
Concerning point (1) in your latest comment. Please see the entry entitled "Crests" http://pterosaurnet.blogspot.com/2010/05/crests.html Your question is explicitly answered in the comments to that entry.
It really would save both of us a lot of time if you read the site.
Concerning number (2) I do not see the problem. Oviraptors evolved from pterosaurs that had beaks. Some retained them and some lost them, over time. What do you see as the problem with that?
"Concerning number (2) I do not see the problem. Oviraptors evolved from pterosaurs that had beaks. Some retained them and some lost them, over time. What do you see as the problem with that?"
Hello Anonymous. Which part? That oviraptors evolved from pterosaurs? Or that, through the evolution process, traits can be lost? This whole site makes the case for the idea that non-modern-bird maniraptors (primitive birds) such as oviraptors, evolved from pterosaurs. And the idea that through the evolution process, traits can be lost, is a standard evolution theory idea.
Well frankly all of it. You state that oviraptors evolved from a pterosaur that had a beak. Did dromaeosaurs? Did Ornitholestes? How about the therizinosaurs? Because you seem to be suggesting multiple origins for the maniraptorans now. And what about Incisivosaurus? Its an oviraptoran without a beak. Surely that means in your phylogeny that in the transition between pterosaurs and oviraptorans they lost and then re-evolved the beak?
And you're seriously suggesting that material that is structurally similar to that in the beak- i.e. a particular sort of keratin became feathers, at the same time as another totally unrelated structure, the actinofibrils- "the complex fibres of the pterosaur wing membrane"- also became feathers? Despite being made of collagen, a totally different substance?
What is your evidence? Again, all I see is an empty assertion.
You posted: "Well frankly all of it. You state that oviraptors evolved from a pterosaur that had a beak. Did dromaeosaurs? Did Ornitholestes? How about the therizinosaurs? Because you seem to be suggesting multiple origins for the maniraptorans now. And what about Incisivosaurus? Its an oviraptoran without a beak. Surely that means in your phylogeny that in the transition between pterosaurs and oviraptorans they lost and then re-evolved the beak?"
I do not understand the "lost and then re-evolved the beak" part. Can you be specific? What creature lineage "lost and re-evolved" a beak?
I have been analyzing the pterosaurs to see if they actually had beaks as we use the term "beak". Rhamphorhynchoid stands for "prow beaks". This kind of "beak" is not the extending kind of beak that we associate with the word "beak". When pterosaurs evolved into primitive birds, it may well be that the most basal primitive "beakless" birds had snouts like prow-beaked pterosaurs. And that "beaks", as we use the word, evolved within the primitive birds. This idea is in line with the fossil record. This idea requires more analysis but it seems right to me at this point.
Dave Godfrey posted: "4. Actinofibrils are most probably made of collagen, a common protein used in supporting tissues. Pycnofibrils are most probably made of keratin, a structure found in the skin., but not within other tissues. Actinofibrils cannot therefore be ancestral to feathers. They are made of different proteins doing different roles."
http://books.google.ca/books?id=idta6AVV-tIC&pg=PA20&lpg=PA20&dq=actinofibrils&source=bl&ots=2E-08Z7eLr&sig=rkiJwNwSZCbYJ9MtkYQDfQ9HDE0&hl=en&ei=0ureTJSDKMienAe_3pXtDw&sa=X&oi=book_result&ct=result&resnum=3&ved=0CCUQ6AEwAg#v=onepage&q=actinofibrils&f=false This link explains that: "Since they [actinofibrils] were external, they were probably epidermal structures composed of keratin as in scales and feathers."
Sadly that source is wrong. Padian and Rayner are wrong in their interpretation of actinofibrils. All the evidence is that they are internal- the holotype of Jehelopterus shows this very well. There are multiple overlapping layers of actinofibrils.
"The specimen of J. ningchengensis adds new information to this discussion. There seems little doubt that the actinofibrils are, in fact, structural fibres, contradicting Pennycuick's (1988) interpretation as superficial wrinkles introduced by elastic fibres. Actinofibrils are internal structures, favouring Wellnhofer's (1987) assumption, and no evidence was found that they are positioned on the ventral part of the plagiopatagium and therefore directly associated with the epidermis as supposed by Padian & Rayner (1993). "
The actinofibrils "form the dorsal surface". See page 20 of the following link: http://books.google.ca/books?id=idta6AVV-tIC&pg=PA20&lpg=PA20&dq=actinofibrils&source=bl&ots=2E-08Z7eLr&sig=rkiJwNwSZCbYJ9MtkYQDfQ9HDE0&hl=en&ei=0ureTJSDKMienAe_3pXtDw&sa=X&oi=book_result&ct=result&resnum=3&ved=0CCUQ6AEwAg#v=onepage&q=actinofibrils&f=false
"Since they [actinofibrils] were external, they were probably [dorsal] epidermal structures composed of keratin as in scales and feathers."
Tischlinger was a co-author of the Jehelopterus study Dave Godfrey referred to which brings with it new data from a well preserved fossil with a lot of soft tissue detail. So that study arguably supersedes the ones Chatterjee mentions and it also clarifies Tischlinger and Frey's position which seems to have been over simplified in that Google books quote:
"Lastly, Tischlinger & Frey (2002) and Frey et al. (2003), based on a Rhamphorhynchus specimen from Solnhofen and an exceptionally well-preserved material from the Romualdo Formation (DGM 1475-R) of Brazil (Martill & Unwin 1989; Kellner 1996), interpreted the pterosaur plagiopatagium as consisting of five layers from dorsal to ventral: a thin and ‘hairless’ epidermis, a spongy subdermis, a layer of actinofibrils, a layer of dermal muscles and a vascular layer. Regarding the last model, it should be noted that Kellner (1996) regarded the soft tissue present in the specimen of the Romualdo Formation as closely associated with the body.
The specimen of J. ningchengensis adds new information to this discussion. There seems little doubt that the actinofibrils are, in fact, structural fibres, contradicting Pennycuick's (1988) interpretation as superficial wrinkles introduced by elastic fibres. Actinofibrils are internal structures, favouring Wellnhofer's (1987) assumption, and no evidence was found that they are positioned on the ventral part of the plagiopatagium and therefore directly associated with the epidermis as supposed by Padian & Rayner (1993). "
"Actinofibrils are unusual structures and we are not sure exactly what they are composed of. The best guess is collagen, but it could also be cartilage or keratin. Determining this in fossils is obviously near impossible but all three are realistic possibilities, though of course collagen is the most likely given the position of the fibres inside the wing membrane (rather than on the surface) and they do not connect to the bones of the wing finger. They lie sub-parallel to the wing towards the wingtips and then sub-perpendicular as we move more proximally. There are no actinofibrils in the proximal wing close to the body, and they get more densely packed the further away you go."
1) Tischlinger himself has contributed to a later study than the one you were quoting from, documenting a more recent and complete fossil, that repudiates the view that actinofibrils were external.
2) The quote I provided from that study also demonstrates that the book chapter you quoted over simplified Tischlinger & Frey (2002) by saying they argued actinofibrils were "external" - in fact even then they found there was "a layer of a thin and ‘hairless’ epidermis", and "a spongy subdermis" above the actinofibril layer.
Anonymous you can help me with this. The quote says that they "interpreted the pterosaur plagiopatagium as consisting of five layers from dorsal to ventral: a thin and ‘hairless’ epidermis, a spongy subdermis, a layer of actinofibrils, a layer of dermal muscles and a vascular layer." This means that the actinofibrils are external to the muscles and the vascular layer. Only skin (the epidermis) and the spongy subdermis are over the actinofibrils. This means to me that they were "external". But I am not looking for an argument. Please explain why this is not "external" to you.
You have a strange definition of external if that's the case. I'm using the term "external" as most people do to mean something that is outside of the body rather than inside it such as on the skin as are hair or feathers (which seemed to be also what you were implying - that actinofibrils could have become feathers). If you are meaning it another way then maybe you need to define your use of the term.
Perhaps you are using it in a relative way for example? - so you might say the ribs are external to the heart. However because this would be confusing to most people (as most people take external to mean on the outside) professional anatomists use the terms superficial/deep to denote relative depths. So anatomists would say the ribs are superficial to the heart and the heart is deep in relation to the ribs. If you are using external=superficial please say so but be aware that this is not how professional anatomists would tend to use the term and therefore not how most of authors we are discussing would or at least should use it - in fact if they were using it that way (e.g. they could say actinofibrils are "external" to the muscle and vascular layers even though they are clearly also internal to the epidermis and spongy layers) one could see how you might become confused which proves my point. Precision in terminology is important for good reason.
To clarify further then - most people would consider anything that is below the skin (especially as in this case they are below 2 tissue layers) as internal. For example, we have numerous tendons and nerves that are closer to the surface than our muscles; does that make them external too?
We are agreeing on the facts and are now arguing whether the word "external" is the best word to use. And we should keep in mind that I was not the one who used the word "external" but the researchers did. My point is that the actinofibrils developed into feathers. I would rather spend time analyzing that, rather than debating the researchers use of the word "external". Especially when you and I already agree on the facts.
We are not agreeing on the facts so don't try and twist my words. Something covered by 2 layers of tissue is clearly not "external" no matter how you try and play with words and certainly not likely to be homologous with feathers.
We agree on the idea of the 5 layers. Why do you say it is "certainly not likely to be homologous with feathers"? Is that simply your personal feeling about it or do you have some evidence and/or references to support that?
If you are agreeing with me on the 5 layers then, as I said already, that makes actinofibrils internal (beneath 2 layers of tissue), not external. If they are internal how could they be homologous with feathers?
We are both accepting the research which shows the 5 layers. In the transition from pterosaur to primitive bird the somewhat sturdy actinofibrils (which are already in the basic shape of feathers) evolved into feathers. And the rest of the membrane was lost. This is not complicated.
The actinofibrils were under the skin and another dermal layer - how would that even happen without evolutionary pressures acting on their aerodynamic properties if they were buried under 2 layers of tissue? It makes no sense that they lost those 2 layers and then emerged from the skin as feathers and the fact is there are much better candidates for ancestral feathers in (funnily enough) proto-feathers. Also Actinofibrils were not feather shaped or in the positions feathers are in- where on Earth did you get that idea?
Actinofibrils are feather shaped and in exactly the same positions as feathers are in in the descendants of pterosaurs. I have covered this in the entries on this blog. Type "actinofibril" into the search function and take a look. I am certainly interested in exploring this with anyone who is interested.
I read what you have written about actinofibrils but I find no support for them being feather shaped. Perhaps you need to show where you have examined them - can you draw a picture or provide a photograph? Also they are certainly not in the same position as feathers (I presume you mean flight feathers). If you had done any research into this you should know that. They have a completely different function to feathers. If you think otherwise again the onus is on you to provide evidence.
Why would they lose their skin? It makes no sense, this is not something that has any precedents - how would something like that be selected for even? Again if you have evidence for such an event I'd love to see it.
When you typed in "actinofibril" into the search function 3 entries came up. Each of those entries has references to scientific, peer-reviewed material which include pictures and photographs. Did you check them out? I am not repeating everything again, just for you. If you want to discuss this you will need to make some effort. But if you are willing to make an effort, I am delighted to work together with you.
Yes I have seen them and not one shows them to be in a feather shape or orientation. I did note that in only a couple of places was there any actual comment from yourself and that it mostly took the form of allusion rather than explicit analysis "what do you see?" sort of thing. That is most unscientific. A true scientist would be clear and explicit - not seek to keep playing guessing games with people. I presume if you had researched this subject extensively you would be able to support your claim but sadly that does not seem to be the case.
Here is an excellent reference that I link to: http://books.google.ca/books?id=8CKYxcylOycC&pg=PA243&lpg=PA243&dq=tenopatagium&source=bl&ots=SopV9CAGec&sig=-gWOltWiFGplrU9tcXV8X8pBPUI&hl=en&ei=vyTjS5aEBoT6lwf_uMC9Ag&sa=X&oi=book_result&ct=result&resnum=6&ved=0CC8Q6AEwBQ#v=onepage&q=tenopatagium&f=false pages 241 - 244
Well that's a bit better - at least you are finally coming up with something worth discussing now but I don't see how this supports your claims. They are really excellent detailed pictures (you should also see the versions under ultra Violet - Dave Hone showed some of various fossils on his site) but the authors themselves interpret these structures as a network of blood vessels intermeshed with structural fibres (the actinofibrils) and muscle fibrils (which are also clearly visible in image d). There is nothing here to suggest that the actinofibrils have a feather-like structure (if there was you would think they would have drawn attention to that as it would be of major interest) and as they mostly run parallel and sub-parallel to the main finger of the wing they are not the same orientation that wing feathers would be in.
Also, as I said before, if they are below the surface it is difficult to conceive of any mechanism for evolutionary forces to have acted on them to change their form and function from internal structural fibres to external aerodynamic feathers. Nor is it necessary given that a more parsimonious ancestor for feathers is already available - protofeathers (whether you choose to see these as a dinosaurian structure of as the same as pycnofibres is another question we can leave to one side for now).
It would be a bit more accurate to say that finally you are looking at the material I referenced in my posts. Right?
Also you have said: "they mostly run parallel and sub-parallel to the main finger of the wing they are not the same orientation that wing feathers would be in." In fact that is the orientation of wing feathers.
And dinosuar "protofeathers" are only called "protofeathers" because of the ASSUMPTION of the dino to bird thoery. See Frances James material.
Eventually you will realize that I have researched this and do know what I am talking about.
You have said: "Also, as I said before, if they are below the surface it is difficult to conceive of any mechanism for evolutionary forces to have acted on them to change their form and function from internal structural fibres to external aerodynamic feathers."
Basically what is required is for the membrane material to be lost.
Can you link to where on your site you have provided this reference before so I can see it in context?
As for position - in the pterosaur actinofibrils are running parallel and sub parallel to the main finger, a finger birds do not even have, so how on Earth you could say they are in the same position is beyond me. If their origins were in attachment points to that finger (as is the case with feathers) they would have been lost with the finger. Neither are feathers in a parallel and sub parallel position in relation to the finger (and other bones) they do attach to as can be seen in any picture of a bird wing:
If you think that is "parallel" then you are using that word in your own special way just as you were using "external" earlier. That doesn't make for clear communication or demonstrate your understanding.
As for your mechanism - yes I realise you said the membrane is lost but that is not a mechanism, your just repeating here what you think happened (which is obvious) but not the why or how - I was asking for how that could happen (i.e. an evolutionary mechanism)? Leaving aside the fact that again you have no evidence this happened (i.e no fossils or developmental evidence and the last is particularly important as you'd expect there to be some) the actinofibrils are under the epidermis and another subdermal layer - birds do still have an epidermis (and secondary dermal layers), it's just that feathers are on top of it, not below it.
Oh yes I have read your posts but this link was hidden as a hyperlink I mistook just as an emphasis - I see it now, finally, but didn't see it before because I was reading with my eyes, not using my mouse. You should provide proper references for your sources instead of hiding them in hyperlinks you can only see are links if you mouse over them.
That being said there isn't much by way of analysis in your posts, you tend to just quote long pieces of text with a few ambiguous comments here and there. I would have thought if you were interested in transparency you would be more explicit in your analysis, evidencing and referencing. This is the first thing students of science learn (in fact we drum it into them very persistently)
Actually I will tell you what is funny. I generally do give the actual link but since this particular link is huge I chose to make it a link rather than paste the entire address. And also the article itself is a PDF and I could not figure out how to copy and paste the diagrams which I really wanted to do and generally do as you know. Also I have covered a huge amount of material and do not have the time to spell out every particular point in the detail I would like. All the material is available through the links. So someone like you can see all the background material that has gone into the conclusions I give.
You have said: "Neither are feathers in a parallel and sub parallel position in relation to the finger (and other bones) they do attach to as can be seen in any picture of a bird wing: http://upload.wikimedia.org/wikipedia/commons/3/35/Birdwing.svg"
In your bird picture, the most distal feathers are parallel to the fingers and as you move in toward the body the feathers become sub-parallel. Just as we see with the actinofibrils in pterosaur wings.
Why do birds share the following features with dinosaurs? Why aren't they present in pterosaurs?
ReplyDeleteEctopterygoid lateral to transverse flange of pterygoid; postfrontal absent; temporal muscles extend anteriorly onto skull roof; quadrate head laterally exposed; S-shaped neck; dorsal vertebrae shorter; at least 3 fully incorporated sacral vertebrae (with 3rd incorporated from dorsal vertebrae); forelimb < 50% length of rear (reversals in several groups); deltopectoral crest extends further down humerus; humerus with elongate deltopectoral crest; manus 4 with <4 phalanges; claws on 1-3 only; semi-perforate (usually fully perforated) acetabulum with buttress; brevis shelf on ilium; ischium with obturator process restricted to anterior 1/3rd; femur with ball-like head; medial tuberosity of femur reduced; shaft of femur straight or bowed anteriorly; femur vertical; femur has greater, lesser & 4th trochanters; tibia with cnemial crest; well-developed ascending process of astragalus on anterior face of tibia; calcaneum with concave surface for articulation of fibula; metatarsals elongate and function as part of pes
Why do birds share the following features with theropods? (note that pneumatisation is present in many theropods, including ones you don't think are anything to do with birds). Why aren't they present in pterosaurs?
ReplyDeleteSkull pneumatized; nares formed by premaxilla & nasals, excluding maxilla; nasal cavities communicate laterally to large diverticula at antorbital fossa; promaxillary fenestra usually present at anteroventral apex of the antorbital fossa; $ lacrimal extends to top of skull; horns & crests (display?) common; nasals usually unsutured at midline; other diverticula invade palate & peri-orbital bones (antorbital diverticula increase in advanced species.); trend to more anterior-facing orbits and increased brain size; opisthotic and exoccipitals always fused; $ intramandibular joint present; external mandibular fenestra present; posterior end of angular usually anterior to articular; long palatine-maxilla suture; some have diverticula from throat through middle ear to braincase; angular with anterior hook; teeth usually laterally compressed, curved, with 2 serrated edges; normally 23 pre-sacral vertebrae; prominent prong-shaped cervical vertebral epipophyses (lost in some advanced species.); long caudal prezygapophyses; limb bones extensively pneumatized, as are ribs & vertebrae; diverticula may communicate with lungs; strap-like scapula; humerus <50% of femur; metacarpals I-III dorsally pitted (ligament attachments); phalanges of hand elongate; loss or reduction of manus 4 & 5; $ claws, especially on manus, long curved & sharp; ilia large and blade-like; expanded distal end of pubes ("pubic boot"); astragalus tends to enlarge, calcaneum to be reduced lost; astragalus with pronounced ascending process; metatarsals tend to increase in size relative to femur; pes 1 tends to develop large "raptor" claw; metatarsals II & IV come in contact & metatarsal III reduced (shock-absorbing arctometatarsalia)
And why do they share the following features with all coelurosaurians? Why aren't they present in pterosaurs?
ReplyDeleteNasals do not participate in antorbital fossa; expanded, circular orbit; jugals reach antorbital fenestrae; Fenestra in roof of mouth; <16 caudals have transverse processes; "boat-shaped" chevrons; fused sternal plates; "cranial notch" between scapula & coracoid absent; coracoid with well-developed posterior projection; elongated forelimbs, especially manus; semilunate carpal in wrist; metacarpal I reduced; long, thin metacarpal III ; $ ischium reduced to <2/3 length of pubis; loss of ischial foot; triangular obturator process on ischium; generally femur substantially shorter than epipodialia; $ ascending process of astragalus >25% length of tibia; knee and ankle hinge-like; fibula reduced and immobile in relation to tibia; tarsal bones elongated; metatarsal III pinched between II & IV (arctometatarsalian condition or similar)
And why do pterosaurs have the following characters that, bar two or three aren't present in birds?
ReplyDeleteLarge eyes; sizeable brains; hollow long bones; sternum (but small or no ossified keel); long retroverted scapula as in birds; ventral edge of coracoid articulates with sternum as in birds and supports pectoral girdle; expanded sternum with keel; humerus longer than sternum; big deltopectoral crest on proximal. humerus for flight stroke muscles; primitively, deltopectoral crest has straight edges; forearm longer than humerus; pteroid bone in wrist; hand with elongate digit 4 supporting wing membrane; manus 1-3 retained, with unguals, and at least sometimes robust; wing membranes with fibers for stiffening; short pubis with pre-pubic bones; highly mobile hip joint; femur bowed and shorter than tibia; fibula reduced and fused to tibia; mesotarsal ankle; 4 elongated, closely appressed metatarsals plus reduced 5th; pes with 5 digits; pes 5 small & without claws; longish penultimate phalanges on feet (not digitigrade?); wing membrane extends to leg in some or all groups, even between rear legs (uropatagium); pteroid supports additional membrane to neck; fibers in membrane; typical gait may have been quadrupedal and plantigrade, with limbs at least partly sprawling; bones generally highly pnematic or hollow & supported by internal struts; integument possibly with hair-like pilosity.
Note here that the ones that they do share with birds can generally be seen to be convergent- the pterosaur sternum is made of different bones to the bird one. (It includes the clavicles for instance).
To make this manageable I will refer to the top post as (A), the one below it as (B), the one below it as (C), and the lowest one (immediately above) as (D).
ReplyDeleteThe other thing we need to be clear about is distinguishing between maniraptors and non-maniraptor theropods.
We cannot use the label "dinosaur" because that will be confusing.
So my questions to you, to begin with:
In (A) by "dinosaur" do you mean non-maniraptor theropods?
In (B) by "theropod" do you mean non-maniraptor theropods?
In (C) by "coelurosaurians" do you mean non-maniraptor coelurosaurians?
Also we need to agree on what "bird" means.
Does "bird" mean?
All maniraptors?
Avialae?
Aves?
Neornithines?
Something else?
Also it will be helpful to me if you give me the link where I can see the source of the characteristics you have listed in (A), (B), (C) and (D).
Ground rules:
I do not allow swearing or personal insults on this site.
No. A is all dinosaurs, saurischians and ornithischians. B is all theropods including maniraptorans. C is all coelurosaurians including maniraptorans. I'd refer to bird as Avialae in that list. But I'd prefer not to use the name for clarity I think.
ReplyDeleteYour reference is www.Palaeos.com
The problem with not distinguishing between maniraptors and non-maniraptors dinosaurs (theropods, coelurosians) is that the maniraptors are birds and the non-maniraptors are dinosaurs. So if we do not make that distinction we are mixing dinosaurs and birds together.
ReplyDeleteSo, if for example you list a characteristic that you believe is found in "dinosaurs" it may be the case that it is only found in the maniraptors (and not in the non-maniraptors) and therefore supports the pterosaur to bird theory but not the dino to bird theory. There are posts on the site that go into this topic at length.
I am quite willing to take bird" as aviale when you use it. Each time I want to refer to "bird" I will follow it with the name (maniraptor) since all creatures currently labeled as maniraptors are birds.
If I wish to distinguish bird groups within "maniraptor" I will refer to the specific group name.
Thanks for the link. Palaeos.com is a fairly large site. Could you please give me the specific page address. That would be great.
While I await your response to my comment that we need to distinguish between maniraptors and non-maniraptor dinosaurs, I will respond to comment (D).
ReplyDeleteYou have said:
"And why do pterosaurs have the following characters that, bar two or three aren't present in birds?"
By "bird" you mean "avialae".
For the purposes of this question that is still not precise enough because it includes both primitive birds such as enantiornithes and modern birds. And as you know the pterosaur to bird theory proposes that pterosaurs evolved into primitive birds and those primitive birds evolved into modern birds.
As a general answer to your question, I would say that if any characteristic is found in a pterosaur but is not found in modern birds, then that characteristic was modified or lost in the progression from pterosaur to primitive bird to modern bird.
For example, the pteroid evolved into the alula so that charateritic is found in modern birds.
The long 5th digit of the pterosaur (which your source incorrectly called the 4th) shortened in the evolution from pterosaur to primitive bird.
Etc.
In Comment (A) you posted:
ReplyDelete"Why do birds share the following features with dinosaurs? Why aren't they present in pterosaurs?"
I will begin with the question "Why aren't they present in pterosaurs"?
If any characteristic is found in a modern bird but is not found in any pterosaur, then that characteristic evolved in the progression from pterosaur to primitive bird to modern bird.
This is standard evolution.
Concerning the non-maniraptor dinosaurs - if any characteristic is found in a modern bird and also found in a non-maniraptor dinosaur it is convergent evolution.
But please provide evidence that any of the characteristics you listed are indeed in non-maniraptor dinosaurs and also in modern birds.
In Comment (B) you posted:
ReplyDelete"Why do birds share the following features with theropods? (note that pneumatisation is present in many theropods, including ones you don't think are anything to do with birds). Why aren't they present in pterosaurs?"
I will begin with the question "Why aren't they present in pterosaurs"?
If any characteristic is found in a modern bird but is not found in any pterosaur, then that characteristic evolved in the progression from pterosaur to primitive bird to modern bird.
This is standard evolution.
Concerning the non-maniraptor theropods - if any characteristic is found in a modern bird and also found in a non-maniraptor theropod it is convergent evolution.
But please provide evidence that any of the characteristics you listed are indeed in non-maniraptor theropods and also in modern birds.
In Comment (C) you posted:
ReplyDelete"And why do they share the following features with all coelurosaurians? Why aren't they present in pterosaurs?"
I will begin with the question "Why aren't they present in pterosaurs"?
If any characteristic is found in a modern bird but is not found in any pterosaur, then that characteristic evolved in the progression from pterosaur to primitive bird to modern bird.
This is standard evolution.
Concerning the non-maniraptor coelurosaurians - if any characteristic is found in a modern bird and also found in a non-maniraptor coelurosaurian it is convergent evolution.
But please provide evidence that any of the characteristics you listed are indeed in non-maniraptor coelurosaurians and also in modern birds.
If you're just going to include maniraptorans in avialae then just use "maniraptorans", because I want to keep "Avialae" to discuss the conventional meaning- Modern Birds (as conventionally defined) plus Archaeopteryx and all the species in between. Avialae is characterised by a series of features that are not present in any other maniraptorans
ReplyDeleteSo each of those characters in each of those posts is convergent evolution? Because they aren't found in pterosaurs, but they are found in maniraptorans (Avialae, Deinonychosauria, Oviraptorosauria, etc). But those characteristics are found in virtually all dinosaurs/theropods/coelurosaurians (depending on the post we're looking at.) They're how we recognise Ovirpator, for example, as being a coelurosaurian/theropod/dinosaur, and not a pterosaur. It has the characters used to define coelurosaurians. It does not have the characters used to recognise pterosaurs. Do you not see why the fact that because this list is so long, and the list linking pterosaurs and birds (hollow bones and your misidentified fingers) is so short should tell you something?
Start with Dinosauria, and work your way down the cladogram to birds. They list references in the diagnosis, which you can trace back to the original papers.
You said:
ReplyDelete"If you're just going to include maniraptorans in avialae..."
I did not say that. Avialae is included in maniraptora.
I am willing to use "avialae" when appropriate.
You said:
"But those characteristics are found in virtually all dinosaurs/theropods/coelurosaurians (depending on the post we're looking at."
You are claiming that the listed characteristics are found in both maniraptors and non-maniraptor coelurosaurians.
Please provide evidence for that assertion with reference links. And also show that they are characteristics unique to non-maniraptor coelurosaurians and not just general archosaur traits.
Note: The dino to bird theory claims that birds evolved from non-maniraptor coelurosaurians.
Concerning the length of the lists. I just gave two examples of traits that relate pterosaurs to modern birds. This site has dozens and dozens. Have you read the entries on this site?
As a general point I am not interested in investigating a whole bunch of dinosaur characteristics.
ReplyDeleteThose who propose the dino to bird theory can do that.
I am interested in the links between pterosaurs and primitive birds and the links between primitive birds and modern birds.
And in fact this site gives dozens and dozens of those.
Concerning the lists that Dave Godfrey gave, what interests me is how those traits relate to pterosaurs and birds. And I will post on that.
Some (possibly most) have already been covered on the site already.
So for example:
ReplyDeleteAll the traits in Comment (A) are claimed by Dave Godfrey to be present in birds but not present in pterosaurs. That interests me.
All the traits in Comment (B) are claimed by Dave Godfrey to be present in birds but not present in pterosaurs. That interests me.
All the traits in Comment (C) are claimed by Dave Godfrey to be present in birds but not present in pterosaurs. That interests me.
All the traits in Comment (D) are claimed by Dave Godfrey to be present in pterosaurs but not present in birds. That interests me.
The traits I have listed are diagnostic characters for the three dinosaurian clades. Your reference is Palaeos. Read it. Move through the cladogram, clicking the links. It references its claims in the scientific literature. You can find links to the full references there. You may even find you can get access to the original paper.
ReplyDeleteDinosaurs
Theropods
Coelurosaurians (including maniraptorans)
You have lots of assertions about how dromaeosaurs and birds have similar characters. But nowhere have you managed to link these to the pterosaurs. You state thaty pterosaurs have the same shoulder articulation as enantiornithines, but the part you quote says that... "The coracoid shows a well developed biceps tubercle but lacks a deep coracoidal flange as reported for Changchengopterus" But the biceps tubercle isn't the same as the scapular-coracoidal joint. This is not a character that links birds and pterosaurs. Its two different characters.
All the other characters can similarly be dismissed as convergences- it is not surprising that pterosaurs and birds have large brains given over to processing complex information.
Pterosaurs retain the diapsid skull condition, which birds have lost, although Confusciusornis retains it. This is a primitive character that is also present in crocs. It will not help you.
Birds have a mandibular fenestrae. Pterosaurs do not. Other archosaurs (apart from pterosaurs) all have this too. Why has this been lost, and then re-acquired if pterosaurs are ancestral to birds?
Beaks have evolved multiple times. Turtles have them. Ornithischians have them. Limusaurus (a ceratosaur) has one. Birds have one. A whole series of other diapsids that have nothing to do with archosaurs have them. Such a widely dispersed character is not helpful.
I could go on in this vein.
You have said:
ReplyDelete"You have lots of assertions about how dromaeosaurs and birds have similar characters. But nowhere have you managed to link these to the pterosaurs."
I invite you to read this site. It shows the links - dozens and dozens of them. With specific supporting references.
You have said:
"All the other characters can similarly be dismissed as convergences- it is not surprising that pterosaurs and birds have large brains given over to processing complex information."
If all the dozens and dozens of characters that link pterosaurs to birds, that I have posted about, are convergences that can be dismissed as convergences, then whatever traits that you claim link non-maniraptor coelurosaurians to maniraptors can similarly be dismissed as convergences.
I am not investigating the dinosaur characteristics for you.
If you wish to propose the dino to bird theory then you can present your case.
I will be analyzing the traits you listed from the pterosaur to bird perspective.
You have said:
ReplyDelete"Beaks have evolved multiple times. Turtles have them. Ornithischians have them. Limusaurus (a ceratosaur) has one. Birds have one. A whole series of other diapsids that have nothing to do with archosaurs have them. Such a widely dispersed character is not helpful."
Are there any non-maniraptor coelurosaurians with beaks? For example, any Compsognathids or Tyrannosaurs with beaks?
You have said:
ReplyDelete"Pterosaurs retain the diapsid skull condition, which birds have lost, although Confusciusornis retains it. This is a primitive character that is also present in crocs. It will not help you.
Birds have a mandibular fenestrae. Pterosaurs do not. Other archosaurs (apart from pterosaurs) all have this too. Why has this been lost, and then re-acquired if pterosaurs are ancestral to birds?"
I covered these topics here:
http://pterosaurnet.blogspot.com/2010/05/skull.html
May I suggest you read it and post any questions there, about what I have said?
You don't mention whether birds have a mandibular fenestrae (they do). You don't mention anything about the pterosaurian postorbital bone. Its not covered there. I read the post. I'm not posting there, because it'll be a pain to find your replies on a post 6 months old. I'd rather keep this conversation here. (To be perfectly honest I'd rather have the conversation at TR).
ReplyDeleteI am not aware of any non-maniraptoran coelurosaur with a beak. But as I pointed out, lots of sauropsids that aren't anything to do with birds have beaks. Its such a widely distributed feature that you can't link its presence in some pterosaurs and its presence in some maniraptorans as being significant.
None of the "dozens of characters you list" are useful. I looked at some above they are not helpful in determining ancestry. They're either not even the same character (the pterosaur shoulder) not homologous (bird and pterosaur crests) too widely distributed among other taxa (beaks), primitive to all archosaurs (through-flow lungs), errors on the websites you quote (feathers are analogous to the thermoregulatory function of pycnofibrils not the wing supporting function of the actinofibrils- the two "fibrils" are very different in composition and structure) and in some cases characters which define maniraptorans (the semi-lunate carpal), but which you don't provide any information about whether they're present in pterosaurs.
So, why are there vastly more characters that unite birds and dinosaurs that aren't clearly adaptations to flight and weight loss, than unite pterosaurs and birds? Your theory is not parsimonious.
You have said:
ReplyDelete"You state thaty pterosaurs have the same shoulder articulation as enantiornithines, but the part you quote says that... "The coracoid shows a well developed biceps tubercle but lacks a deep coracoidal flange as reported for Changchengopterus"
Can you give the link for this please?
I do not remember ever saying that
"pterosaurs have the same shoulder articulation as enantiornithines,"
I've just noticed your posts on bird and pterosaur wrists. You state that-
ReplyDelete"The wing of a modern bird, for example, has only two remaining carpals; the radiale (the scaphoid of mammals) and a bone formed from the fusion of four of the distal carpals."
The bird has a radiale, and ulnare (which are not made of other fused bones) and four distal carpals fused to the metacarpals to form a carpometacarpus.
This is not the same as that seen in pterosaurs. They have three carpals, a distal syncarpal (made of fused bones) and proximal syncarpal (made of fused bones) a medial carpal, and the pteroid (possibly- but there is certainly no indication that it is the thumb anywhere in the peer-reviewed literature). So again the two conditions are not homologous. You need to unfuse the proximal syncarpal to form the radiale and ulnare of birds, fuse the medial carpal and the distal syncarpal to the metcarpals of the hand to form the carpometacarpus. And you need to do even more unfusing to get to the condition in the non-avian maniraptorans.
And if you want the pteroid to be the thumb you have to completely re-evolve the metacarpals, phalanges and claws that are present in maniraptorans.
Scapula/coracoid structure
ReplyDeleteFirst you quote Wikipedia.
"Specifically, in Enantiornithes, the scapular facet of the coracoid is a convex knob [tubercle] and the coracoidal facet of the scapula is a concave dish-shaped excavation to receive it. In neornithes the scapular facet of the coracoid is a round pit, which receives the coracoidal tubercle of the scapula"
Then you quote Xiaolin Wang's description of Wukongopterus
"The coracoid shows a well developed biceps tubercle but lacks a deep coracoidal flange as reported for Changchengopterus"
And you say.
"The pterosaur scapula/coracoid relationship (articulation) is the same as that of the enantiornithes."
The articulation is not the same. The two tubercles are completely different structures.
You have said that you are "not aware of any non-maniraptoran coelurosaur with a beak."
ReplyDeleteYou specifically raised the topic of beaks.
Pterosaurs have beaks.
Non-maniraptoran coelurosaurs do not have beaks. The dino to bird theory is based on the idea that birds evolved from non-maniraptoran coelurosaurs.
On the one definite trait that we have looked at so far and agreed on, the pterosaur to bird theory has been supported and the dino to bird theory has not been supported.
Agreed?
You have said:
ReplyDelete"So, why are there vastly more characters that unite birds and dinosaurs that aren't clearly adaptations to flight and weight loss, than unite pterosaurs and birds? Your theory is not parsimonious."
Can you support that assertion please? To this point you have not done so.
In fact in the one trait that we have agreed on so far, your statement is not correct.
Also you say "that aren't clearly adaptations to flight and weight loss," as if we can simply overlook those characteristics.
Consider this:
One airplane is closer to another airplane than either is to a bicycle and a lot of that is that both planes are able to fly. They have a huge number of characteristics related to the fact that they both can fly. Do we overlook those aspects of them, that give them the ability to fly? You must be joking.
You have said:
ReplyDelete"None of the "dozens of characters you list" are useful. I looked at some above they are not helpful in determining ancestry. They're either not even the same character (the pterosaur shoulder) not homologous (bird and pterosaur crests) too widely distributed among other taxa (beaks), primitive to all archosaurs (through-flow lungs), errors on the websites you quote (feathers are analogous to the thermoregulatory function of pycnofibrils not the wing supporting function of the actinofibrils- the two "fibrils" are very different in composition and structure) and in some cases characters which define maniraptorans (the semi-lunate carpal), but which you don't provide any information about whether they're present in pterosaurs."
This is an odd statement:
"primitive to all archosaurs (through-flow lungs)",
May I suggest you research the subject of flow-through lungs and archosaurs. Your statement is completely incorrect.
I have also covered that subject at length on the site.
May I suggest that you actually read the entries on this site. I am not going to spoon feed you by repeatting one point at a time what I have already covered on the site.
Not at all.
ReplyDeleteBeaks evolved more than once in the pterosauria. Not all pterosaurs have them. Some have beaks and teeth. Some beaks and no teeth. Some teeth and no beaks. Pteranodon and Nyctosaurus have beaks. The various Azdarchoids have beaks. But the pteranodontians aren't Azdarchoids, they're Ornithocheiroids. Most of which have lots of teeth. So this character doesn't help you even if we only look at pterosaurs.
But it gets worse for you. Not all of the avialae had beaks. For example, Archaeopteryx didn't. Not all non-avian maniraptorans had beaks dromaeosaurs and troodontids didn't. Nor did the primitive oviraptorans (Incisivosaurus had very obvious teeth.)
Limusaurus is a non-coelurosaurian theropod. It has a beak. Coelurosaurians share a common ancestor with non-coelurosaurian theropods. And share closer ancestry with some non-coelurosaurian theropods than others. So we have a non-maniraptoran, non-coelurosaurian theropod with a beak. And then we have all the ornithischians with beaks. And then all the things outside archosauria with beaks.#
Its a very common feature. Its evolved many times in many lineages that neither of us think are closely related to birds. It is therefore not helpful to your argument. As its not a character I propose that unites birds and any dinosaurs (because it evolves independently multiple times) it harms your argument not mine.
Your comments about fingers and carpals are completely wrong. I have covered that at great length.
ReplyDeleteThe pteroid bone is the first finger. From that everything else follows smoothly.
It is a vastly interesting subject but I am not going over it all again just for you.
Read the entries.
Alligators have through-flow lungs. There was a paper on it last year. It was discussed in one of your threads on TR. It got its own thread. My statement is in fact completely correct.
ReplyDeleteOh, and you know how aeroplanes don't breed? Its why its a terrible analogy for producing cladograms. But you shouldn't forget the Gossamer Albatross a human powered aeroplane built around a bicycle. You're also totally ignoring the massive differences in how birds and pterosaurs build their wings. Not to mention all the non-flight related things that are totally different. If there was a pattern of relatedness shouldn't they be similar? And yet they're not. And nor, when we look at them, are the details of their wings.
You have posted a comment that begins with:
ReplyDelete"Beaks evolved more than once in the pterosauria. Not all pterosaurs have them......"
This is where the discussion becomes a lot less interesting and a lot less fun for me - when you begin to work up elaborate stories to try cover over a fact that goes against what you are proposing and supports strongly what I am saying.
And not surprising you fall back on the convenient, convergent evolution non-explanation.
Do you think that anybody will think that the fact that pterosaurs have beaks like birds and that the dinosaurs you claim evolved into birds do not, is good for your point of view.
I am not using up my time responding to every just-so story you come up with.
I'm quoting from what you've written about carpals. I read the entries. Both of them. You made a mistake. You're being called on it. Bird and pterosaurs wrists are different. Your quotes show it.
ReplyDelete"Do you think that anybody will think that the fact that pterosaurs have beaks like birds and that the dinosaurs you claim evolved into birds do not, is good for your point of view."
ReplyDeleteI think people will read what I wrote and draw their own conclusions. Beaks are widely distributed among animals that neither of us think are anything to do with direct ancestry of either pterosaurs or birds. That has to be convergence. So when we see multiple origins of beaks in pterosaurs AND maniraptoriformes (Ornithomimids had beaks- are you including them in the "maniraptorans" that belong in pterosaurs or not? I forget. And Incisivosaurus has teeth and no beak, but its an oviraptoran- you even have a picture of it- so that's another independent origin for a beak), why is convergence suddenly forbidden as an explanation?
You have said:
ReplyDeleteScapula/coracoid structure
First you quote Wikipedia.
"Specifically, in Enantiornithes, the scapular facet of the coracoid is a convex knob [tubercle] and the coracoidal facet of the scapula is a concave dish-shaped excavation to receive it. In neornithes the scapular facet of the coracoid is a round pit, which receives the coracoidal tubercle of the scapula"
Then you quote Xiaolin Wang's description of Wukongopterus
"The coracoid shows a well developed biceps tubercle but lacks a deep coracoidal flange as reported for Changchengopterus"
And you say.
"The pterosaur scapula/coracoid relationship (articulation) is the same as that of the enantiornithes."
The articulation is not the same. The two tubercles are completely different structures.
Can you please support your assertion that:
"The two tubercles are completely different structures."
You have a comment that begins with:
ReplyDelete"Alligators have through-flow lungs"
Are you claiming that birds evolved from alligators? No you are not.
The question is - did compsognathids or tyrannosaurs have flow through lungs? Remember those are the groups the dino to bird theory claim evolved into birds.
Modern birds have flow through lungs.
Pterosaurs had flow-through lungs.
The groups you claim evolved into birds did not have flow through lungs.
This is another situation like the beaks.
Pterosaurs had the trait that birds have. Non-maniraptor coelurosaurians did not.
Now I will hear all the stories and spin about those facts.
But the facts do not change.
On the two traits that we have talked about and agreed on the facts about, the pterosaur theory has been supported and not the dino to bird theory.
You posted:
ReplyDelete"(Ornithomimids had beaks- are you including them in the "maniraptorans" that belong in pterosaurs or not?"
Yes, I have included maniraptoriformes in the bird group that evolved from pterosaurs.
I mention this on the site.
It really would be good if you read the entries on this site. Instead of just shooting from the hip.
You posted:
ReplyDelete"And Incisivosaurus has teeth and no beak, but its an oviraptoran- you even have a picture of it- so that's another independent origin for a beak),"
Perhaps it is getting late, but how can the fact that Incisivosaurus has no beak be an example of independent origin of a beak?
You have said:
ReplyDelete"I'm quoting from what you've written about carpals. I read the entries. Both of them. You made a mistake. You're being called on it. Bird and pterosaurs wrists are different. Your quotes show it."
Is your argument that the pteroid is not the thumb? Or is there more to it than that?
(I may have been unclear before and called it the first finger. I should call it the thumb for clarity).
You posted:
ReplyDelete"You're also totally ignoring the massive differences in how birds and pterosaurs build their wings."
Actualy I have studied at length the way pterosaur wings are built. Recent research ahs shown them to very complicated structures.
And although I have not posted on this topic it is fascinating to see that the counterparts to the feather structures are already in prototpye version in the pterosur wing.
And recently they have even found protofeather material on the pterosaur wing.
The main changes required are to shorten the 5th finger, fuse the non-pteroid fingers into the bird form, lose the webbing material and elaborate the actinofibrils into feather structures. There is more, but that is the heart of it.
It really is quite interesting.
Dave Godfrey, you posted:
ReplyDelete"...not homologous (bird and pterosaur crests)"
Can you support that assertion please?
I will address some items in Comment (D):
ReplyDelete"And why do pterosaurs have the following characters that, bar two or three aren't present in birds?
Large eyes; sizeable brains; hollow long bones; sternum (but small or no ossified keel); long retroverted scapula as in birds; ventral edge of coracoid articulates with sternum as in birds and supports pectoral girdle; expanded sternum with keel; humerus longer than sternum; big deltopectoral crest on proximal. humerus for flight stroke muscles; primitively, deltopectoral crest has straight edges; forearm longer than humerus; pteroid bone in wrist; hand with elongate digit 4 supporting wing membrane; manus 1-3 retained, with unguals, and at least sometimes robust; wing membranes with fibers for stiffening; short pubis with pre-pubic bones; highly mobile hip joint; femur bowed and shorter than tibia; fibula reduced and fused to tibia; mesotarsal ankle; 4 elongated, closely appressed metatarsals plus reduced 5th; pes with 5 digits; pes 5 small & without claws; longish penultimate phalanges on feet (not digitigrade?); wing membrane extends to leg in some or all groups, even between rear legs (uropatagium); pteroid supports additional membrane to neck; fibers in membrane; typical gait may have been quadrupedal and plantigrade, with limbs at least partly sprawling; bones generally highly pnematic or hollow & supported by internal struts; integument possibly with hair-like pilosity."
Here is an analysis of some of the items in the list:
Birds have "sizeable brains" - like pterosaurs
Birds have "hollow long bones" - like pterosaurs
Birds have "expanded sternum with keel" - like pterosaurs
As the list itself says, "pterosaurs have long retroverted scapula as in birds".
Pterosaurs have "hand with elongate digit 4 [actually it is digit 5] supporting wing membrane". The elongate 5th digit shortened in the evolution to primitive bird.
Pterosaurs had "wing membranes with fibers for stiffening". Those evolved into feathers.
Pterosaurs have "wing membrane extends to leg in some or all groups, even between rear legs (uropatagium)". The membrane was lost with the evolution of feathers.
The pterosaur's "pteroid supports additional membrane to neck". In the evolution to bird, the pteroid became the alula and the membrane was lost.
Birds have "bones generally highly pnematic or hollow & supported by internal struts" - like pterosaurs
It is said of pterosaurs that they have "integument possibly with hair-like pilosity."
These are protofeathers.
Concerning Comment(D), I missed this obvious one directly from the list:
ReplyDelete"ventral edge of coracoid articulates with sternum as in birds and supports pectoral girdle".
I was thinking about the traits listed in Comment (D). Something seemed wrong about it. Then I realized that it did not include a great number of traits and aspects of pterosaurs. Here is some additional info that brings to light the enormous similarity of birds to pterosaurs, in addition to what I have said above.
ReplyDeletehttp://en.wikipedia.org/wiki/Pterosaur
"Pterosaur bones were hollow and air filled, like the bones of birds. They had a keeled breastbone that was developed for the attachment of flight muscles and an enlarged brain that shows specialised features associated with flight.[4] In some later pterosaurs, the backbone over the shoulders fused into a structure known as a notarium, which served to stiffen the torso during flight, and provide a stable support for the scapula (shoulder blade).
As evidenced by hollow cavities in the wing bones of larger species and soft tissue preserved in at least one specimen, some pterosaurs extended their system of respiratory air sacs into the wing membrane itself.
Most pterosaur skulls had elongated, beak-like jaws. Some advanced forms were toothless (such as the pteranodonts and azhdarchids, though most sported a full complement of needle-like teeth
Unlike most archosaurs, which have several openings in the skull in front of the eyes, in pterodactyloid pterosaurs the antorbital opening and the nasal opening was merged into a single large opening, called the nasoantorbial fenestra. This likely evolved as a weight-saving feature to lighten the skull for flight
Pterosaurs are well known for their often elaborate crests.
The presence of pycnofibres (and the demands of flight) imply that pterosaurs were endothermic (warm-blooded).
The mechanics of pterosaur flight are not completely understood or modeled at this time[22][23], but it is almost certain that this group of animals was capable of powered flight in at least as wide a range of conditions as modern birds.
The wings were probably flapped in a manner grossly similar to that seen in birds (a group which displays many different flapping strategies among and within different species and different situations).
A 2009 study showed that pterosaurs had a lung-air sac system and a precisely controlled skeletal breathing pump, which supports a flow-through pulmonary ventilation model in pterosaurs, "analogous" to that of birds. The presence of a subcutaneous air sac system in at least some pterodactyloids would have further reduced the density of the living animal
The pterosaurs' flocculi occupied 7.5% of the animals' total brain mass, more than in any other vertebrate. Birds have unusually large flocculi compared with other animals, but these only occupy between 1 and 2% of total brain mass
Pterosaur's hip sockets are oriented facing slightly upwards, and the head of the femur (thigh bone) is only moderately inward facing, suggesting that pterosaurs had a semi-erect stance.
Pteranodon had slightly larger feet (47% the length of the tibia), while filter-feeding pterosaurs like the ctenochasmatoids had very large feet (69% of tibial length in Pterodactylus, 84% in Pterodaustro), adapted to walking in soft muddy soil, similar to modern wading birds
It is not known whether pterosaurs practiced any form of parental care, but their ability to fly as soon as they emerged from the egg and the numerous flaplings found in environments far from nests and alongside adults has led most researchers, including Christopher Bennett and David Unwin, to conclude that the young were only dependent on their parents for a very short period of time, while the wings grew long enough to fly, and left the nest to fend for themselves within days of hatching."
1. The bird crests you discuss are made of feathers. Pterosaur crests are made of bone with a horny coating. If you want a structure to which they are homologous you would do better to look at cow or Triceratops horns. At least they're made of the same material. But not all pterosaurs have crests. Not all birds have crests either. And lots of dinosaurs have crests too. So this feature is not helpful too you. Like beaks it is too widely dispersed to tell you enough.
ReplyDelete2. Not all Avialans have beaks. Archaeopteryx does not have one. Not all pterosaurs have beaks. Incisivorosaurus is important because most oviraptorans have beaks, but it is a very primitive one. And does not have a beak. So beaks have evolved independently in Oviraptorans, because the most primitive member lacks one, but later ones have them.
3. Your reference for the Coracoidal Tubercule is Wikipedia.
"The coracoid tubercle is a prominent area on the anterior surface of the coracoid, just ventral to the shoulder socket (glenoid). The coaracoid tubercle forms the pointed portion in those coracoids described as "flexed". It was previously called the biceps tubercle because it was thought to be the origin of the M.biceps muscle. Makovicky & Sues (1998) followed Alick Walker (1990) in asserting that it is, instead, probably the origin of the M. coracobrachialis muscle."
It is not the same structure as the tubercle that forms the shoulder joint in the enantiornithines.
4. Actinofibrils are most probably made of collagen, a common protein used in supporting tissues. Pycnofibrils are most probably made of keratin, a structure found in the skin., but not within other tissues. Actinofibrils cannot therefore be ancestral to feathers. They are made of different proteins doing different roles.
5. Birds have smaller flocculi than pterosaurs. Why? Birds have an erect gait. Pterosaurs do not. But dinosaurs are pretty much unique among archosaurs in having an erect gait. So its more parsimonious to believe that this is not convergent.
6. Birds have through-flow lungs. Alligators have through-flow lungs. Sauropods have through-flow lungs. Maniraptorans have through-flow lungs. Theropods have through-flow lungs. All of these preserve either evidence of air sacs or have experimental data to back up these conclusions. Ornithischians probably had through-flow lungs, but their bones weren't permeated by air sacs. This is therefore almost certainly a basal feature present in all archosaurs.
7. That list of pterosaur characters includes several that you claim aren't mentioned. (Like their semi-erect gait). Or are only present in a few taxa and are therefore not characteristic of pterosaurs as a whole, but only a few species or specific groups (the nasoaneorbital fenestrae is a diagnostic character of pterodactyloids. Not Pterosauria as a whole. Which is what that list is about). Or are most likely present in all archosaurs. (The "lung-air sac system" you mention.
8 What is your peer-reviewed reference that pterosaurs have retained digit 1 as the pteroid bone? It is not quoted anywhere. You state that everyone's made this mistake many times, but you never actually provide any anatomical reason why we should agree with your diagnosis. What specimens have you studied that allow you to make this judgement?
Concerning point (1) in your latest comment.
ReplyDeletePlease see the entry entitled "Crests"
http://pterosaurnet.blogspot.com/2010/05/crests.html
Your question is explicitly answered in the comments to that entry.
It really would save both of us a lot of time if you read the site.
Concerning number (2) I do not see the problem. Oviraptors evolved from pterosaurs that had beaks.
ReplyDeleteSome retained them and some lost them, over time.
What do you see as the problem with that?
"Concerning number (2) I do not see the problem. Oviraptors evolved from pterosaurs that had beaks.
ReplyDeleteSome retained them and some lost them, over time.
What do you see as the problem with that?"
There is no evidence of this
Hello Anonymous.
ReplyDeleteWhich part? That oviraptors evolved from pterosaurs? Or that, through the evolution process, traits can be lost?
This whole site makes the case for the idea that non-modern-bird maniraptors (primitive birds) such as oviraptors, evolved from pterosaurs.
And the idea that through the evolution process, traits can be lost, is a standard evolution theory idea.
Well frankly all of it. You state that oviraptors evolved from a pterosaur that had a beak. Did dromaeosaurs? Did Ornitholestes? How about the therizinosaurs? Because you seem to be suggesting multiple origins for the maniraptorans now. And what about Incisivosaurus? Its an oviraptoran without a beak. Surely that means in your phylogeny that in the transition between pterosaurs and oviraptorans they lost and then re-evolved the beak?
ReplyDeleteAnd you're seriously suggesting that material that is structurally similar to that in the beak- i.e. a particular sort of keratin became feathers, at the same time as another totally unrelated structure, the actinofibrils- "the complex fibres of the pterosaur wing membrane"- also became feathers? Despite being made of collagen, a totally different substance?
What is your evidence? Again, all I see is an empty assertion.
You posted:
ReplyDelete"Well frankly all of it. You state that oviraptors evolved from a pterosaur that had a beak. Did dromaeosaurs? Did Ornitholestes? How about the therizinosaurs? Because you seem to be suggesting multiple origins for the maniraptorans now. And what about Incisivosaurus? Its an oviraptoran without a beak. Surely that means in your phylogeny that in the transition between pterosaurs and oviraptorans they lost and then re-evolved the beak?"
I do not understand the "lost and then re-evolved the beak" part.
Can you be specific? What creature lineage "lost and re-evolved" a beak?
The lineage leading from pterosaurs (beaked) through basal oviraptors (Incisvorsaurus beakless) to derived oviraptors (beaked).
ReplyDeleteThe bird lineage too. From pterosaurs (beaks) to dromaeosaurs (no beaks) to "primitive birds" (no beaks) and then modern birds (beaks).
Pretty much every lineage like that.
I have removed a couple of posts that were not correct.
ReplyDeleteIs that comments from this thread? Or whole posts from your blog? And if the former who wrote them?
ReplyDeleteI have been analyzing the pterosaurs to see if they actually had beaks as we use the term "beak". Rhamphorhynchoid stands for "prow beaks". This kind of "beak" is not the extending kind of beak that we associate with the word "beak".
ReplyDeleteWhen pterosaurs evolved into primitive birds,
it may well be that the most basal primitive "beakless" birds had snouts like prow-beaked pterosaurs.
And that "beaks", as we use the word, evolved within the primitive birds.
This idea is in line with the fossil record.
This idea requires more analysis but it seems right to me at this point.
The comments I removed were mine.
ReplyDeleteThe comment immediately above represents my thinking at this time.
Dave Godfrey posted:
ReplyDelete"4. Actinofibrils are most probably made of collagen, a common protein used in supporting tissues. Pycnofibrils are most probably made of keratin, a structure found in the skin., but not within other tissues. Actinofibrils cannot therefore be ancestral to feathers. They are made of different proteins doing different roles."
http://books.google.ca/books?id=idta6AVV-tIC&pg=PA20&lpg=PA20&dq=actinofibrils&source=bl&ots=2E-08Z7eLr&sig=rkiJwNwSZCbYJ9MtkYQDfQ9HDE0&hl=en&ei=0ureTJSDKMienAe_3pXtDw&sa=X&oi=book_result&ct=result&resnum=3&ved=0CCUQ6AEwAg#v=onepage&q=actinofibrils&f=false
This link explains that:
"Since they [actinofibrils] were external, they were probably epidermal structures composed of keratin as in scales and feathers."
Sadly that source is wrong. Padian and Rayner are wrong in their interpretation of actinofibrils. All the evidence is that they are internal- the holotype of Jehelopterus shows this very well. There are multiple overlapping layers of actinofibrils.
ReplyDelete"The specimen of J. ningchengensis adds new information to this discussion. There seems little doubt that the actinofibrils are, in fact, structural fibres, contradicting Pennycuick's (1988) interpretation as superficial wrinkles introduced by elastic fibres. Actinofibrils are internal structures, favouring Wellnhofer's (1987) assumption, and no evidence was found that they are positioned on the ventral part of the plagiopatagium and therefore directly associated with the epidermis as supposed by Padian & Rayner (1993). "
The soft tissue of Jeholopterus (Pterosauria, Anurognathidae, Batrachognathinae) and the structure of the pterosaur wing membrane. Kellner et al. Proc. R. Soc. B 22 January 2010 vol. 277 no. 1679 321-329
They are internal structures not closely associated with the epidermis. They are therefore unlikely to be made of keratin.
The actinofibrils "form the dorsal surface".
ReplyDeleteSee page 20 of the following link:
http://books.google.ca/books?id=idta6AVV-tIC&pg=PA20&lpg=PA20&dq=actinofibrils&source=bl&ots=2E-08Z7eLr&sig=rkiJwNwSZCbYJ9MtkYQDfQ9HDE0&hl=en&ei=0ureTJSDKMienAe_3pXtDw&sa=X&oi=book_result&ct=result&resnum=3&ved=0CCUQ6AEwAg#v=onepage&q=actinofibrils&f=false
"Since they [actinofibrils] were external, they were probably [dorsal] epidermal structures composed of keratin as in scales and feathers."
This is based on Tischlinger and Frey (2002) who "documented this convincingly".
ReplyDeleteTischlinger was a co-author of the Jehelopterus study Dave Godfrey referred to which brings with it new data from a well preserved fossil with a lot of soft tissue detail. So that study arguably supersedes the ones Chatterjee mentions and it also clarifies Tischlinger and Frey's position which seems to have been over simplified in that Google books quote:
ReplyDelete"Lastly, Tischlinger & Frey (2002) and Frey et al. (2003), based on a Rhamphorhynchus specimen from Solnhofen and an exceptionally well-preserved material from the Romualdo Formation (DGM 1475-R) of Brazil (Martill & Unwin 1989; Kellner 1996), interpreted the pterosaur plagiopatagium as consisting of five layers from dorsal to ventral: a thin and ‘hairless’ epidermis, a spongy subdermis, a layer of actinofibrils, a layer of dermal muscles and a vascular layer. Regarding the last model, it should be noted that Kellner (1996) regarded the soft tissue present in the specimen of the Romualdo Formation as closely associated with the body.
The specimen of J. ningchengensis adds new information to this discussion. There seems little doubt that the actinofibrils are, in fact, structural fibres, contradicting Pennycuick's (1988) interpretation as superficial wrinkles introduced by elastic fibres. Actinofibrils are internal structures, favouring Wellnhofer's (1987) assumption, and no evidence was found that they are positioned on the ventral part of the plagiopatagium and therefore directly associated with the epidermis as supposed by Padian & Rayner (1993). "
From here:
http://rspb.royalsocietypublishing.org/content/277/1679/321.full#xref-ref-38-1
Authors: Alexander W. A. Kellner1,Xiaolin Wang2, Helmut Tischlinger, Diogenes de Almeida Campos, David W. E. Hone and Xi Meng
Note Dave Hone also discuses this in his blog here:
http://archosaurmusings.wordpress.com/2008/06/16/pterosaur-wings-2-structure/
"Actinofibrils are unusual structures and we are not sure exactly what they are composed of. The best guess is collagen, but it could also be cartilage or keratin. Determining this in fossils is obviously near impossible but all three are realistic possibilities, though of course collagen is the most likely given the position of the fibres inside the wing membrane (rather than on the surface) and they do not connect to the bones of the wing finger. They lie sub-parallel to the wing towards the wingtips and then sub-perpendicular as we move more proximally. There are no actinofibrils in the proximal wing close to the body, and they get more densely packed the further away you go."
Anonymous can you do me a favor and specify exactly what point you are making please?
ReplyDeleteI thought it was obvious but I'll summarise.
ReplyDelete1) Tischlinger himself has contributed to a later study than the one you were quoting from, documenting a more recent and complete fossil, that repudiates the view that actinofibrils were external.
2) The quote I provided from that study also demonstrates that the book chapter you quoted over simplified Tischlinger & Frey (2002) by saying they argued actinofibrils were "external" - in fact even then they found there was "a layer of a thin and ‘hairless’ epidermis", and "a spongy subdermis" above the actinofibril layer.
Anonymous you can help me with this.
ReplyDeleteThe quote says that they "interpreted the pterosaur plagiopatagium as consisting of five layers from dorsal to ventral: a thin and ‘hairless’ epidermis, a spongy subdermis, a layer of actinofibrils, a layer of dermal muscles and a vascular layer."
This means that the actinofibrils are external to the muscles and the vascular layer. Only skin (the epidermis) and the spongy subdermis are over the actinofibrils.
This means to me that they were "external".
But I am not looking for an argument. Please explain why this is not "external" to you.
You have a strange definition of external if that's the case. I'm using the term "external" as most people do to mean something that is outside of the body rather than inside it such as on the skin as are hair or feathers (which seemed to be also what you were implying - that actinofibrils could have become feathers). If you are meaning it another way then maybe you need to define your use of the term.
ReplyDeletePerhaps you are using it in a relative way for example? - so you might say the ribs are external to the heart. However because this would be confusing to most people (as most people take external to mean on the outside) professional anatomists use the terms superficial/deep to denote relative depths. So anatomists would say the ribs are superficial to the heart and the heart is deep in relation to the ribs. If you are using external=superficial please say so but be aware that this is not how professional anatomists would tend to use the term and therefore not how most of authors we are discussing would or at least should use it - in fact if they were using it that way (e.g. they could say actinofibrils are "external" to the muscle and vascular layers even though they are clearly also internal to the epidermis and spongy layers) one could see how you might become confused which proves my point. Precision in terminology is important for good reason.
To clarify further then - most people would consider anything that is below the skin (especially as in this case they are below 2 tissue layers) as internal. For example, we have numerous tendons and nerves that are closer to the surface than our muscles; does that make them external too?
We are agreeing on the facts and are now arguing whether the word "external" is the best word to use.
ReplyDeleteAnd we should keep in mind that I was not the one who used the word "external" but the researchers did.
My point is that the actinofibrils developed into feathers.
I would rather spend time analyzing that, rather than debating the researchers use of the word "external".
Especially when you and I already agree on the facts.
We are not agreeing on the facts so don't try and twist my words. Something covered by 2 layers of tissue is clearly not "external" no matter how you try and play with words and certainly not likely to be homologous with feathers.
ReplyDeleteWe agree on the idea of the 5 layers.
ReplyDeleteWhy do you say it is "certainly not likely to be homologous with feathers"?
Is that simply your personal feeling about it or do you have some evidence and/or references to support that?
If you are agreeing with me on the 5 layers then, as I said already, that makes actinofibrils internal (beneath 2 layers of tissue), not external. If they are internal how could they be homologous with feathers?
ReplyDeleteWe are both accepting the research which shows the 5 layers.
ReplyDeleteIn the transition from pterosaur to primitive bird the somewhat sturdy actinofibrils (which are already in the basic shape of feathers) evolved into feathers. And the rest of the membrane was lost.
This is not complicated.
The actinofibrils were under the skin and another dermal layer - how would that even happen without evolutionary pressures acting on their aerodynamic properties if they were buried under 2 layers of tissue? It makes no sense that they lost those 2 layers and then emerged from the skin as feathers and the fact is there are much better candidates for ancestral feathers in (funnily enough) proto-feathers. Also Actinofibrils were not feather shaped or in the positions feathers are in- where on Earth did you get that idea?
ReplyDeleteActinofibrils are feather shaped and in exactly the same positions as feathers are in in the descendants of pterosaurs.
ReplyDeleteI have covered this in the entries on this blog.
Type "actinofibril" into the search function and take a look.
I am certainly interested in exploring this with anyone who is interested.
By the way the feathers do not "emerge" from the skin as feathers. The skin is simply lost. As is the rest of the membrane.
ReplyDeleteI read what you have written about actinofibrils but I find no support for them being feather shaped. Perhaps you need to show where you have examined them - can you draw a picture or provide a photograph? Also they are certainly not in the same position as feathers (I presume you mean flight feathers). If you had done any research into this you should know that. They have a completely different function to feathers. If you think otherwise again the onus is on you to provide evidence.
ReplyDeleteWhy would they lose their skin? It makes no sense, this is not something that has any precedents - how would something like that be selected for even? Again if you have evidence for such an event I'd love to see it.
When you typed in "actinofibril" into the search function 3 entries came up. Each of those entries has references to scientific, peer-reviewed material which include pictures and photographs. Did you check them out?
ReplyDeleteI am not repeating everything again, just for you. If you want to discuss this you will need to make some effort.
But if you are willing to make an effort, I am delighted to work together with you.
Yes I have seen them and not one shows them to be in a feather shape or orientation. I did note that in only a couple of places was there any actual comment from yourself and that it mostly took the form of allusion rather than explicit analysis "what do you see?" sort of thing. That is most unscientific. A true scientist would be clear and explicit - not seek to keep playing guessing games with people. I presume if you had researched this subject extensively you would be able to support your claim but sadly that does not seem to be the case.
ReplyDeleteHere is an excellent reference that I link to:
ReplyDeletehttp://books.google.ca/books?id=8CKYxcylOycC&pg=PA243&lpg=PA243&dq=tenopatagium&source=bl&ots=SopV9CAGec&sig=-gWOltWiFGplrU9tcXV8X8pBPUI&hl=en&ei=vyTjS5aEBoT6lwf_uMC9Ag&sa=X&oi=book_result&ct=result&resnum=6&ved=0CC8Q6AEwBQ#v=onepage&q=tenopatagium&f=false
pages 241 - 244
See particularly Figure 4 on page 241.
ReplyDeleteWell that's a bit better - at least you are finally coming up with something worth discussing now but I don't see how this supports your claims. They are really excellent detailed pictures (you should also see the versions under ultra Violet - Dave Hone showed some of various fossils on his site) but the authors themselves interpret these structures as a network of blood vessels intermeshed with structural fibres (the actinofibrils) and muscle fibrils (which are also clearly visible in image d). There is nothing here to suggest that the actinofibrils have a feather-like structure (if there was you would think they would have drawn attention to that as it would be of major interest) and as they mostly run parallel and sub-parallel to the main finger of the wing they are not the same orientation that wing feathers would be in.
ReplyDeleteAlso, as I said before, if they are below the surface it is difficult to conceive of any mechanism for evolutionary forces to have acted on them to change their form and function from internal structural fibres to external aerodynamic feathers. Nor is it necessary given that a more parsimonious ancestor for feathers is already available - protofeathers (whether you choose to see these as a dinosaurian structure of as the same as pycnofibres is another question we can leave to one side for now).
It would be a bit more accurate to say that finally you are looking at the material I referenced in my posts. Right?
ReplyDeleteAlso you have said:
"they mostly run parallel and sub-parallel to the main finger of the wing they are not the same orientation that wing feathers would be in."
In fact that is the orientation of wing feathers.
And dinosuar "protofeathers" are only called "protofeathers" because of the ASSUMPTION of the dino to bird thoery.
See Frances James material.
Eventually you will realize that I have researched this and do know what I am talking about.
I suggest you read the blog more carefully.
You have said:
ReplyDelete"Also, as I said before, if they are below the surface it is difficult to conceive of any mechanism for evolutionary forces to have acted on them to change their form and function from internal structural fibres to external aerodynamic feathers."
Basically what is required is for the membrane material to be lost.
Not at all since you have not referred to that specific link before in any of your posts on actinofibrils -
ReplyDeletehttp://pterosaurnet.blogspot.com/search?q=actinofibril.
Can you link to where on your site you have provided this reference before so I can see it in context?
As for position - in the pterosaur actinofibrils are running parallel and sub parallel to the main finger, a finger birds do not even have, so how on Earth you could say they are in the same position is beyond me. If their origins were in attachment points to that finger (as is the case with feathers) they would have been lost with the finger. Neither are feathers in a parallel and sub parallel position in relation to the finger (and other bones) they do attach to as can be seen in any picture of a bird wing:
http://upload.wikimedia.org/wikipedia/commons/3/35/Birdwing.svg
If you think that is "parallel" then you are using that word in your own special way just as you were using "external" earlier. That doesn't make for clear communication or demonstrate your understanding.
As for your mechanism - yes I realise you said the membrane is lost but that is not a mechanism, your just repeating here what you think happened (which is obvious) but not the why or how - I was asking for how that could happen (i.e. an evolutionary mechanism)? Leaving aside the fact that again you have no evidence this happened (i.e no fossils or developmental evidence and the last is particularly important as you'd expect there to be some) the actinofibrils are under the epidermis and another subdermal layer - birds do still have an epidermis (and secondary dermal layers), it's just that feathers are on top of it, not below it.
The link is on this page.
ReplyDeletehttp://pterosaurnet.blogspot.com/2010/05/pterosaur-wing-covering-2.html
Have you actually read the posts?
Oh yes I have read your posts but this link was hidden as a hyperlink I mistook just as an emphasis - I see it now, finally, but didn't see it before because I was reading with my eyes, not using my mouse. You should provide proper references for your sources instead of hiding them in hyperlinks you can only see are links if you mouse over them.
ReplyDeleteThat being said there isn't much by way of analysis in your posts, you tend to just quote long pieces of text with a few ambiguous comments here and there. I would have thought if you were interested in transparency you would be more explicit in your analysis, evidencing and referencing. This is the first thing students of science learn (in fact we drum it into them very persistently)
Actually I will tell you what is funny. I generally do give the actual link but since this particular link is huge I chose to make it a link rather than paste the entire address. And also the article itself is a PDF and I could not figure out how to copy and paste the diagrams which I really wanted to do and generally do as you know.
ReplyDeleteAlso I have covered a huge amount of material and do not have the time to spell out every particular point in the detail I would like. All the material is available through the links. So someone like you can see all the background material that has gone into the conclusions I give.
Here is the post that is being referred to:
ReplyDeletehttp://pterosaurnet.blogspot.com/2010/05/pterosaur-wing-covering-2.html
You have said:
ReplyDelete"Neither are feathers in a parallel and sub parallel position in relation to the finger (and other bones) they do attach to as can be seen in any picture of a bird wing:
http://upload.wikimedia.org/wikipedia/commons/3/35/Birdwing.svg"
In your bird picture, the most distal feathers are parallel to the fingers and as you move in toward the body the feathers become sub-parallel. Just as we see with the actinofibrils in pterosaur wings.