Tuesday, February 15, 2011


Turning back to the development of pterosaurs to modern birds:

It is believed that dinosaurs and pterosaurs were Ornithodirans.
The dinosaurs went their way on the land and the pterosaurs went their way in the air.
The pterosaurs developed into primitive birds.
It is no wonder that those primitive birds (maniraptors) had some similarity to dinosaurs.

Ornithodira --> Dinosaurs
Ornithodira --> Pterosaurs --> Maniraptors --> Modern birds

The similarities of dinosaurs and maniraptors are symplesiomorphic.
To visualize the idea I am expressing you can think of it this way:
Very early on there was a split of creatures into one line that became land-based dinosaurs and another line that became air-based pterosaurs. Over time, each line developed to adapt to their ecological niche.
The pterosaurs developed through a series of steps to primitive birds (maniraptors) and eventually modern birds.
The dinosaurs on the land developed at the same time on their own line, but eventually died off.
Similarities between dinosaurs and the maniraptors is due to their common origin as ornithodirans.
Those similarities are symplesiomorphic.


  1. Some recent studies also support a prolacertiform (as sister taxon to Sharovipteryx or Drepanosauridae) origin for pterosaurs (Renesto & Binelli (2006)), although the discovery that Dimorphodon and a jaw referred to Eudimorphodon have mandibular fenestrae (as well as the possession of air sacs, and, if pycnofibres are homologous to protofeathers, a filamentous covering seems to support an archosaur, specifically avemetatarsalian origin for pterosaurs. I think the second one is more likely, but, since the origins of pterosauria are still pretty unclear (Dave Peters even suggested they were lepidosauromorphs), I wouldn't base your argument on the supposed ancestral traits of avemetatarsalia/ornithodira. Also, based on what you've said, the characteristics you've described are homoplasies, not symplesiomorphies, because pterosaurs do not share these characteristics. If these "dinosaurian" traits were symplesiomorphies, this would imply that maniraptorans are not dinosaurs or pterosaurs.

  2. I am not basing my argument on the supposed ancestral traits of avemetatarsalia/ornithodira.
    That is just one idea.

    And in regards to your second point
    "Also, based on what you've said, the characteristics you've described are homoplasies, not symplesiomorphies, because pterosaurs do not share these characteristics."

    What "characteristics" are you referring to?

  3. A saurischian pelvis structure (Saurischia), possibly a hand composed of the digits II, III and IV (Tetanurae), an elongated sacrum (coelurosauria), a bowed ulna (Coelurosauria, unambiguous mandibular fenestra (arhcosauria, some advanced members of archosauriformes), enlarged clavicle (coelurosauria), medullary bone (dinosauria), etc.

  4. To begin with the first one:
    The saurischian dinosaur pelvic structure is not like the maniraptors.
    The ornithiscian dinosaur pelvic structure is like maniraptors.

    Saurischians are distinguished from ornithischians by their three-pronged pelvic structure, with the pubis pointed forward. The ornithischians' pelvis is arranged with the pubis rotated backward, parallel with the ischium, often also with a forward-pointing process, giving a four-pronged structure.

    The ornithischian hip structure is superficially similar to that of birds, which led Seeley to name them "bird-hipped dinosaurs," though he did not propose any specific relationship with birds. He termed saurischians "lizard-hipped" dinosaurs because they retained the ancestral hip anatomy also found in modern lizards.

  5. Yes saurischians have a hip that is in some ways similar to a lizard pelvis, but a saurischian pelvis is much more elongated, and you would never confuse the two. Maniraptoran pelvises are different from those of other saurischians, but they are pretty much just saurischian pelvises with a backwards pointing pubis.

  6. You have said:
    "Maniraptoran pelvises are different from those of other saurischians"

    Manirpators are not saurischians. So maniraptors are not "other saurischians". You keep trying to slip your ideas in like this.

    Earlier you had said that the saurischian pelvis structure was like the maniraptor pelvis structure. I have now shown that they are not.
    Maniraptors have a backward pointing pubis.
    It will hardly do for you to say that other than that they are pretty much the same.

  7. Turning to another characteristic that you have listed - "medullary bone".
    This is symplesiomorphic since pterosaurs also have this characteristic.
    "This study also documents the presence of what appears to be medullary bone tissue within the medullary cavity of a large femur of Pterodaustro. This suggests that, like birds, reproductively active female pterosaurs may have deposited a special bone tissue (medullary bone) to cope with the demand of calcium during eggshelling."

  8. Turning to the sacrum that you mentioned.
    Birds are like pterosaurs.

    "When multiple sacral vertebrae are fused into a single structure, it is called the sacrum. The synsacrum is a similar fused structure found in birds that is composed of the sacral, lumbar, and some of the thoracic and caudal vertebra, as well as the pelvic girdle."

    The [pterosaur] sacrum is a block of vertebrae that are fused together and fused to their respective ribs to form a solid, structurally strong, unit.

  9. You keep saying I'm "slipping", slipping on what? (and don't say "your bias") I said that maniraptoran pelvises are like those of other saurischians, because they are most similar to those of non-maniraptoran pelvises and bird pelvises, a kind of intermediate. Also, you have said (in your summary!), "The creatures labeled "maniraptoriformes" are not dinosaurs, but are flying birds and secondarily flightless birds, within the separate bird line", but non-maniraptoran maniraptoriforms (Ornithomimosaurs, Ornitholestes (which is often considered a basal maniraptoran), Haplocheirus, etc.) do not have a backwards pointing pubis, instead they have a regular saurischian pelvis. Notice any inconsistencies there?
    Ok, fine pterosaurs have medullary bone, I was unaware, but so do dinosaurs, so that neither supports nor detracts from either theory.

  10. When you respond you include in your post (you "slip in") your own opinion right into the way you state things.
    For example you said:
    "Maniraptoran pelvises are different from those of other saurischians".

    Here you have slipped in the idea that maniraptors are saurischians - which is simply the unsupported point you are trying to make. And yet you slip it in as if it were a fact.

    Are you blind to what you are doing?

  11. No, I simply mean that a backwards pointing pubis is an autapomorphy of derived maniraptorans. Maniraptorans having a modified saurischian pelvis doesn't make them not dinosaurs, believe it or not, there are groups within groups. Also, Pterosaurs have a prepubic bone, as well as a fused pubis and ischium which sweeps back is shaped kind of like an ax head, which no dinosaurs or birds have (although some derived ornithischians have a prepubic bone too, does this mean that some ornithischians aren't dinosaurs and are pterosaurs instead?). So did maniraptorans lose the pre-pubic one, fused pubiis and ischium, and develop a saurischian pelvis independently?

  12. We have already seen that maniraptors did not have a saurischian pelvis.
    Why do you keep talking as if they did?
    You are wasting my time and your own.

  13. And by the way, a backwards pointing pubis is not an autapomorphy of just derived maniraptorans.
    The earliest maniraptors (eg. dromaeosaurids) had a backwards pointing pubis.
    You still cannot get the dino to bird idea out of your mind and actually consider what I am saying. It is like your mind has been programmed and you cannot think beyond that programming.

  14. Dromaeosaurs are among the most derived maniraptorans, more basal maniraptorans would be things like therizinosaurs, ornitholestes (which I already said didn't have a backwards pointing pubis), etc. I know you said earliest, but that also isn't true, troodontids, pedopenna, scansoriopterygids, ornitholestes, and archaeopteryx all show up earlier than dromaeosaurids.

  15. Dromaeosaurs date back to 167 mya.

    "Dromaeosaurid fossils have been found in North America, Europe, Africa, Japan, China, Mongolia, Madagascar, Argentina, and Antarctica.[2] They first appeared in the mid-Jurassic Period (Bathonian stage, 167 million years ago) and survived until the end of the Cretaceous (Maastrichtian stage, 65.5 ma), existing for over 100 million years, up until the Cretaceous–Tertiary extinction event. The presence of dromaeosaurs as early as the Middle Jurassic has been confirmed by the discovery of isolated fossil teeth, though no dromaeosaurid body fossils have been found from this epoch.[3]"

    None of the others you listed go back that far.

  16. Those supposed mid jurassic "dromaeosaurs" are based on based on teeth which lack any identifying characteristics beyond "paraves", which means they could also be from a troodontid or some weird archaeopteryx-like thing, and since other teeth found in the formation were identified as being from ricardoestesia (which I highly doubt, given their age, but they could be a close relative of ricardoestesia), and ricardoestesia is another (poorly known) "paravian", these teeth only show that there were "paravians" present in the mid jurassic. The unnamed unit in which they were from is late bathonian (the very end of the middle jurassic), so it would be closer to 164 million years old, although I don't know how reliable the date is since it hasn't been named yet. The tiaojishan formation, which contains anchiornis, a definite troodontid, is from the late bathonian or early oxfordian, so there were probably also troodontids in the mid jurassic. The daohugou beds may also be from the middle jurassic, and if this is the case, then epidexipteryx, scansoriopteryx, and pedopenna date to around the same time as these russian "dromaeosaurs". Currently, there are no unambiuous mid jurassic dromaeosaurs, although they probably existed then, since troodontidae is the sister taxon of dromaeosauridae, they just haven't been found yet, that is, if they will ever be found. Also, earliest isn't the same thing as most primitive; ornitholestes is a more primitive maniraptoran (it may not be a maniraptoran, but as it possesses a "sickle claw" and some other characterisics unique to maniraptorans, I think it probably is) but shows up slightly later (mid kimmeridgian) than these other forms.

  17. I am happy to work with you django but I am not sure what you are getting at.
    I had said that Dromaeosaurs date back to 167 mya and that none of the others you listed go back that far.

    That is the current thinking based on the fossil evidence.

    Your post contains lots of things that "could be" but then there is also a lot of unfound evidence that "could" further support what I am saying if we want to go beyond the fossil evidence.
    Let's stay with what is known now and not indulge in what "could be".
    What is known now supports what I have proposed.

  18. "Those supposed mid jurassic "dromaeosaurs" are based on based on teeth which lack any identifying characteristics beyond "paraves", which means they could also be from a troodontid or some weird archaeopteryx-like thing, and since other teeth found in the formation were identified as being from ricardoestesia (which I highly doubt, given their age, but they could be a close relative of ricardoestesia), and ricardoestesia is another (poorly known) "paravian", these teeth only show that there were "paravians" present in the mid jurassic. The unnamed unit in which they were from is late bathonian (the very end of the middle jurassic), so it would be closer to 164 million years old, although I don't know how reliable the date is since it hasn't been named yet."
    did you understand a single word I said?

  19. Django, if you have nothing but silly sarcasm why are you using up your time here?

  20. I'm confused. Before Anchiornis was discovered, how were scientists concluding that birds descended from dinosaurs? We know Archaeopteryx lived 150mya. Most of the "feathered dinosaurs" found in Liaoning Province are from ca 130mya. I'm curious as to why it was never proposed that perhaps the Liaoning specimens were descended from Archaeopteryx? Archaeopteryx appears in the fossil record with fully developed flight feathers indistinguishable from a modern birds. So perhaps this trait was passed down from an even more bird-like ancestor, and the Liaoning creatures are actually the "watered-down" versions if you will. Please clear this up, i find this incredibly fascinating just can't seem to understand the scientists reasoning.


  21. I do not agree with the dinosaur to bird theory.
    I am not the right person to ask.

    Keep in mind that the dino-to-bird folks no longer even think that Archaeoptryx was an ancestor of modern birds.

  22. There is no evidence whatsoever, at all, that avialans are pterosaurs. How can you explain the feathered dinosaurs? the temporal paradox doesn't exist, some scansoriopterygids lived in the Middle Jurassic.
    Archaeopteryx was a feathered dinosaur, but was not an Aves but an Avialae.

  23. Hello Taylor.
    Have you read the posts in this blog?

  24. Yes, I have.
    Also, there are no transitional fossils between pterosaurs and birds, note that.
    But there are transitionals between dinosaurs and birds... HMMM... I think that should get us somewhere.
    Okay, look at my avatar image, its a Scansoriopteryx and its a dinosaur.
    I know you want to take out the Maniraptoriformes and place it in the Pterosauria, but that seems just so wrong, because it is....
    Phylogenetics disagree with anything that says dinosaurs didn't evolve into birds, as do characters.
    My final point, pterosaurs have pycnofibres, dinosaurs even outside of the Maniraptoriformes have feathers and protofeathers.

  25. Hello Taylor.
    If there is some specific post that I have made that you disagree with please tell me which one and why you disagree with it.

  26. Manioraptors are saurischians,because they, like lizard-hipped saurischians, have very mobile digits.And no pterosaurs have filaments except Sordes.A few primitve ornithisitchian dinosaur have filaments. And other non-manioraptorans like tyrannosaurs have feathers. Pterosaurs had four phalanxes in their wing finger, while the alula has two.Chickens were made to regrow teeth and theylooked liked dino teeth. This blog is erroneous.

  27. Are you saying that tyrannosaurs are the ancestors of birds?
    If you wish to respond please include a made-up name next time.
    Also if you are going to make assertions please include references that support your assertions.
    And copy and paste what you think is the relevant material.

  28. Pterosaur teeth are like bird teeth:

    Most pterosaur teeth are relatively smooth with an oval section and no ridges. They tend to taper evenly to the tip and can be straight or gently curved along their length.
    It is worth knowing that pterosaur material is rare and can command a good price on the market. Pterosaur teeth are also rare and it is unusual to find large quantities of them. Several other fossil species show similarities with pterosaur teeth, especially some juvenile crocodiles.

    The researchers recently created more Talpids by tweaking the genes of normal chickens to grow teeth.
    "What we discovered were [bird] teeth similar to those of crocodiles.."

  29. Pterosaur teeth:



  30. Anonymous got it exactly backwards:

    The structure of the avian tarsus has recently been cited as evidence for the derivation of birds from theropod dinosaurs. Although birds and theropods have a long triangular ossification in front of the tibia and attached to the proximal tarsals, the morphological relationships of this bone are fundamentally different in the two groups. In modern birds and in all Mesozoic birds, this "pretibial" bone is a high, narrow structure associated primarily with the calcaneum, but independently ossified. The corresponding structure in dinosaurs is a broad extension of the astragalus. Avian dentitions also pose a problem for the dinosaur hypothesis. While theropod teeth are serrated and have straight roots, avian teeth, like those of crocodilians, are unserrated, with constricted bases and expanded roots.


    I don't know how many times I have seen commenters assert something like what Anonymous did, only to find out that the reality is exactly the opposite of what they have asserted.

  32. Look: Tianyulong has filaments!
    Also look: Dilong, what you say is a dinosaur, looks more like manioraptorans than any Pterosaur!

    And more: Pterosaur teeth go straight, then bend, which bird teeth do not!
    And next time quote me

  33. Tianyolong is an ornithiscian. Are you thinking birds evolved from ornithiscians?

    "The hollow filaments are parallel to each other and are singular with no evidence of branching. They also appear to be relatively rigid, making them more analogous to the integumentary structures found on the tail of Psittacosaurus[2] than to the proto-feather structures found in avian and non-avian theropods."

    You seem to be supporting the idea that birds did not evolve from saurischian dinosaurs.
    Why not consider that birds evolved from pterosaurs?

  34. Also let me say again that the phrase "non-avian theropods" (in the Wikipedia quote) is not helpful.
    It lumps maniraptors (that are primitive birds) in with dinosaurs (that are not birds).

  35. And to cap it all off, Psittacosaurus is an ornithiscian.

  36. It seems almost to be a rule.
    Whenever anyone tries to be specific about the dino to bird theory they list Ornithischian dinosaurs.
    BUT the dino to bird theory is that birds evolved from Saurischian dinosaurs.

    The dino to bird theory does not even pass the simplest examination.

  37. Before I begin, I am going to say that my view is that birds are dinosaurs, and so in this post birds will be labelled as saurischian dinosaurs. I'll also put it into a question-by-question format, to make point and counter-point simpler for both of us. Anyway, SCIENCE HO!

    *flexes science muscles*

    My point here is that a pterosaur's method of doing things is not conductive to evolving into a bird, while a dinosaur's method is.

    Firstly, I believe that is that there is no reason for the pterosaurs to evolve avian wings. Pterosaurs had wings made up of an incredibly complex and sensitive series of tissue, including muscle, air sac and (IIRC) pycnofiber. This also featured three clawed and well-developed feet at the front, and a long, single finger running behind to support the membrane. This created an incredibly adaptable surface, also able to support much larger sizes than in birds. From creatures such as Pterodactylus itself, we can also infer that small pterosaurs had no problem with a wing membrane like this. Let's draw a parallel between a pterosaur and a dinosaur with a similar niche.
    Scaphognathus and Microraptor were both predatory animals. Scaphognathus probably had small fish in its diet, and Microraptor has been recorded with fish in its digestive system. Scaphognathus also probably hunted small pterosaurs, and Microraptor has bird bones in its guts, so it could probably take pterosaurs as well. Both had superficial similarities, but were very different animals.

    The main point here is in the wing. In Scaphognathus, the wing surface is based on the previously-mentioned system. In Microraptor, three long, clawed fingers were used, that were fairly useless for walking on due to the lack of rotation. These wings are of a similar structure to the structures found in adult Ornithomimus, which is a lot more primitive than Microraptor. A pterosaur can use its previously-existing wings to fulfill the niche of early birds without having to evolve feathers, while a dinosaur could not. Since this structure already existed at least one dinosaur, it seems far more likely that a small carnivorous dinosaur with a similar structure used this surface as a flight surface, instead of a pterosaur evolving it independently of dinosaurs and replacing the very good flight surface with what (in early birds and similar creatures) would not have been all that good for flight. Even the probable purposes of incubation or sexual selection would not replace a pterosaur's wings, as the membrane could be used instead of feathers for both purposes.

    1. Very interesting comment.
      I have a few things to say about it. But let me begin with this question for you:
      If you say that there is no reason for the pterosaurs to evolve avian wings then I would say that there is no reason for dinosaurs to evolve avian wings.

    2. Thanks! I try. :)
      I'd disagree with that statement. A pterosaur has wings, and so does not need wings that (at the time) would be inferior to pterosaur wings. However, even inferior wings would allow a carnivorous dinosaur to exploit many new niches.
      Basically, good wings>basic wings>no wings, in regards to my argument. Pterosaurs have good wings, so don't need basic wings. Dinosaurs have no wings, and so would get an advantage from basic wings.

  38. That is an interesting "just-so" story. I could equally provide a "just-so" story. But that is not science.
    I have provided a large website with a huge amount of material. Would you care to address that?

  39. Here is a "just so story" that might appeal.
    Pterosaurs had a very long wing finger. That would be okay out in the open but would be prone to break when flying in a forest and hitting trees and branches. Consequently feathers would be a huge advantage in any kind of forest environment.

  40. Ah-ah-ah, no indirect counterpoints. :P

    In response to that, though, pterosaurs were perfectly capable flyers. They were skilled flyers, and would have been able to avoid branches as well as any bird. A bird's feathers, if caught on trees, would also suffer damage. Both animals would be grounded if they didn't take enough care. In regards to the long-wings argument, many pterosaurs had wings that were smaller and more rounded than that. From a quick look at images of a forest-living bird and a potential forest pterosaur, the harpy eagle and Tapejara, I can fairly safely say that their proportions are rather similar to each other.

    Much of evolution is "just-so" stories. Examples include:
    -Mammals were small creatures during their evolution. However, a combination of traits allowed them to take over when a meteorite wiped out the dinosaurs.
    -A small cichlid was trapped in a lake after the last ice age. It survived, and changed into many different forms.
    In the same way, a small dinosaur with a large surface would be able to use it to jump from tree to tree (or at least closer to it). Those better at gliding would have more effect.

    I believe that this is a satisfactory response. In return, let us get back to the original point. D'ya have any diagrams for the stages of evolution or anything? That would be easiest to visualise.

    Also, a few other areas of difference between birds and pterosaurs and similarities between birds and dinosaurs (as well as the presence of avian wings in the latter group) include eggs and methods of terrestrial locomotion. A pterosaur has leathery eggs, like a crocodile (as inferred from Darwinopterus), while both birds and dinosaurs have hard-shelled eggs. In pterosaurs, one of their biggest advantages is the pole-vault mechanism of takeoff, which allows them to use their already-powerful wing muscles to leave the ground, while birds (like a dinosaur) have strong back legs and use them to leave the ground instead. Why would a pterosaur develop a bipedal stance, when the quadrupedal stance gives them such an advantage?

  41. I do not agree with you about the just-so story I posted.
    Now what?
    Do you see that we cannot base anything on just-so stories.
    Those arguments could go on forever.

  42. You clearly underestimate the pterosaur's flying ability. :P

    We are talking about the adaptation of a single feature (well, technically there's more, but one main one) that created an entirely new and incredibly successful clade of animals: A feature that, by natural selection, was selected as advantageous. Evolution is about advantages. Wings gave a theropod an advantage, therefore evolution would select for wings within that theropod, therefore I have provided proof that this is within evolution and not a baseless "just-so" story. You cannot deny that limited flight would offer new niches to a theropod, even if you disagree that it happened. (This is the part where I'd usually type an evil laugh.)

    Anyway, I believe that we have thoroughly discussed that point. Would you be able to provide sequences of events, providing clear advantages, for the development of:
    -An avian wing, descended from the three claws of the pterosaurian hand, that would replace the already-existing wings
    -A switch from burying eggs to dinosaur-like parental care and hard-shelled eggs
    -A bipedal stance
    in pterosaurs? If I haven't been very clear with what I mean, there's something on Youtube including stuff like 'development of the eye', 'development of the bombadier beetle's spray' and 'development of the flagellum' for how things could develop.

  43. This is not going well.
    We need to base our discussion on evidence and published material.
    Please present reference(s) and copy and paste what you think is the relevant material, for whatever you wish to assert.

  44. You're avoiding the ques-ti-on~ Logic and analysis of known facts is a viable alternative to papers, as that's how those papers were made in the first place.

    I'll give you an example of what I would like to see: A logical progression of how dinosaurs (pterosaurs in your case) evolved into birds.

    1.The ancestor of birds had feathery structures on its arms. (Source: As Ornithomimus, Caudipteryx and paraves have wings, phylogenetic bracketing tells us that their common ancestor had wings.)

    2. These wings were found to be useful for flapping in a number of activities, such as wing-assisted incline running and for stabilisation while attacking prey, and so were selected for it.

    3. Dinosaurs could climb trees. Even unskilled flyers like the hoatzin get an advantage from flight, so flying tree dinosaurs would as well.

    Now, if you can provide a convincing method of how pterosaurs became birds, I may be convinced. If you cannot, I win the debate by default.

  45. The problem with the dino to bird theory is that there is no connection between basal coelurosaur dinosaurs (eg. tyrannosaurs) and basal Paraves.
    Please tell me the lineage from basal coelurosaurs to basal Paraves please. Please tell me the names of the taxa on that line.
    And since it interests you please tell me the selective advantage at each step in that lineage please.


    Just clicked the wrong button. Dangit. Still me here, can't be bothered logging back in. This is what, the fourth time I've accidentally lost the post?

    Tyrannosaurs are advanced coelurosaurs, not primitive ones. Actual primitive coelurosaurs like Compsognathus and Eotyrannus are more similar in body plan to maniraptoriformes, maniraptora and paraves than pterosaurs are.

    I cannot provide specific genera, as we are yet to uncover the fossils. However, we are yet to uncover pterosaur-like paravians or bird-like pterosaurs, while I have provided a logical progression from primitive maniraptoriformes to paravians.

    You have repeatedly asked me to provide more evidence or expand on my theory, instead of providing your own evidence that my theory is not so and your hypothesis is more well-supported. I have made paragraphs, and you have made sentences instead. Due to this, I win. :P

    If you wish to win, then you must provide a logical evolution from pterosaurs to birds.

  47. Earlier I had asked that you support what you are saying with references and copy and paste what you think is the relevant material. You have begun giving references which is good. Please copy and paste from your references what you think is the relevant material.