Aurornis (pre-bird) skull, traced using DGS

Updated July 07, 2015 with new images of Aurornis.

Aurornis xui (Godefroit et al. 2013, Late Jurassic, 50cm in length, 160 or 125mya) is one of the many outgroup taxa known for Archaeopteryx and the birds, but it nests here as the closest of the tested ones.

Auronis is a small, gracile dromaeosaur
without a large elevated pedal digit 2. The skull is complete, but slightly disarticulated (Fig. 1). A little DGS colorizes the bones. These can then be reassembled to form a skull in lateral view.

Fig. 1 Aurornis skull in situ, various elements segregated from the in situ fossil and reassembled into a complete and articulated skull. The hole in the surangular is an artifact. The little lavender ovals are displaced sclerotic bones. Below is the original published image of the Aurornis skull.

Fig. 1 Aurornis skull in situ, various elements segregated from the in situ fossil and reassembled into a complete and articulated skull. The hole in the surangular is an artifact. The little lavender ovals are displaced sclerotic bones. Below is the original published image of the Aurornis skull.

Like many other small theropods,
Aurornis was feathered, agile and fast, a descendant of basal dromaeosaurids, like Halplocheirus. In palatal view, the internal nares are located on the anterior palatines and the anterior palate is narrow but solid. The premaxilla is still relatively short and toothed. The pterygoids are narrow and have lost their primitive triangular shape. As a result of taphonomy, tracings for the anterior dentary teeth are distinct from one another. The wider, more typical, pointed teeth are the correct morphology.

Figure 2. Aurornis in several views alongside Archaeoperyx to scale.

Figure 2. Aurornis in several views alongside Archaeoperyx to scale.

On a side note:
Pappochelys (‘grandfather turtle’) has been getting a lot of press, none critical. Take a fresh look at all the PR here.

On another side note:
Chilesaurus, which the large reptile tree nested as the long sought and current most basal member of the Ornithischia, and we looked at earlier here, was given a good look over at the TheropodDatabase blog here.  Evidently others also think the original Chilesaurus report has issues.

Added July 09, 2015
Dr. Andrea Cau’s note and the paper she sent, along with the SuppData downloaded served to increase the accuracy of these Aurornis images.

Figure 3. The manus of Aurornis as originally interpreted (above). As reinterpreted by comparison to Archaeopteryx below. Digit 3 was damaged and difficult to interpret. Digit 0 was originally overlooked. No only was Archaeopteryx smaller, it was more fully feathered and its bones were more gracile, all adaptations for flight.

Figure 3. The manus of Aurornis as originally interpreted (above). As reinterpreted by comparison to Archaeopteryx below. Digit 3 was damaged and difficult to interpret. Digit 0 was originally overlooked. No only was Archaeopteryx smaller, it was more fully feathered and its bones were more gracile, all adaptations for flight.

I have not seen the fossil itself,
but a DGS tracing of this image of the hand (Fig. 3) suggests ungual 2.3 was buried beneath the m2.2, not absent as originally indicated. Digit 3 of Aurornis was badly damaged, but by comparing it to Archaeopteryx a more accurate interpretation can be rendered with the proper number and length of phalanges.

Godefroit et al. reported the frontal was fused medially, but the fossil shows a medial split. They interpreted the pes with a fused metatarsal 3+4. That is probably not true as metatarsal 4 is likely buried in the matrix.

Figure 5. Aurornis hind limbs with bones colored. Here metatarsal 4 is distinct from mt3 and the fibula is identified. Click to enlarge.

Figure 5. Aurornis hind limbs with bones colored. Here metatarsal 4 is distinct from mt3 and the fibula is identified. Original interpretation of fused mt3+4 in gray. Mt5 is a tiny vestige close to the ankle. Click to enlarge.

References
Godefroit P, Cau A, Hu D-Y, Escuillié, Wu, W-H and Dyke G 201. A Jurassic avialan dinosaur from China resolves the early phylogenetic history of birds. Nature 498 (7454): 359–362.

wiki/Aurornis

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11 thoughts on “Aurornis (pre-bird) skull, traced using DGS

  1. Dear Mister Peters,
    I am Andrea Cau, one of the authors of the paper describing and erecting Aurornis xui. In this moment, I have the actual specimen of Aurornis xui in front of me, the specimen you claimed to reconstruct in this post. The real fossil, not a photo.
    So, I may provide a direct and testable evaluation on the real object of your reconstruction. I’m very sorry if I may result rude, but based on direct observation of the specimen here in front of me, using my eyes and with a stereomicroscope, I must comment that the vast majority of those bones you pictured here (and that are not pictured in our published paper) are not visible in the real fossil under any magnification. None of them, in your picture, represents the real fossil, in both shape and position.
    For example:
    No scleral ring bones are in the fossil.
    No distinct prefrontal is present in the fossil.
    No displaced quadrates are in the fossil.
    No displaced occiput (or whatever you think that blue colored thing is) results in the fossil.
    No additional elements of the ischia are present in the fossil.
    No feathers are present close to the metacarpus in the fossil.

    Furthermore, your reconstruction of the foot is completely speculative and not supported by direct observation:
    The first toe is small, not rotated relative to the other toes, and its ungual is small.
    What you depicted as the large ungual of the first toe is just a crack in the fossil at the level of the real first phalanx of the second toe.
    What you depicted as the diverging end of the fourth metatarsal is the real first phalanx of the first toe.
    What you depicted as the proximal part of the first phalanx of the fourth toe is the real ungual of the first toe.
    What you depicted in the recent post about Balaur as the first phalanx of the first toe is just a hole on metatarsal II, a post-mortem erosion of the fossil.
    Finally, what you depicted as the fifth metatarsal simply does not exist in the real fossil.

    In short, your reconstructions are filled by so many errors and wrong interpretations that cannot be trusted at all.

    Please, I encourage you to stop publishing online these completely fake reconstructions, that are, as this example shows, completely unsupported by actual observation of the real fossils. This is very bad use of internet, spreading pseudo-science and damaging the hard work of the paleontologists.

    Sincerely,

    Andrea Cau

    • Dr. Cau,

      Thank you for your feedback. I hope the corrections I have made here after accessing higher resolution data willl meet with your approval.

      I am concerned with the tone of your note, blackwashing four years of effort. While the specific comments are warranted and appreciated, many would judge the remainder of your reply over the top, emotional and unprofessional. You could have said, “I have some data you may find helpful,’ and left it at that. The progress of science benefits from discussion, something I have always encouraged. However, and I think you’ll understand, making hyperbolic accusations is not appropriate.

      As you know, working from photographs of two-dimensional specimens has proven time and again to be equal to first hand observation and superior whenever sufficient resolution is present and the tracer puts in greater effort. Many paleontologists use photographs and trace bone shapes, especially if the specimen appears chaotic.

      Problems do arise with low-resolution images. Since I work with what is available, those problems persist until better data becomes available. Interestingly, the new scores based on better data do not affect the nesting of Aurornis basal to Archaeopteryx, but they do shift Balaur closer to Velociraptor, as originally nested.

      Like you, I had no idea what to expect the first time I met Aurornis. We both came to the fossil with our own lists of biases and expectations. These affect our perceptions whenever the image or the fossil itself is not clear. That’s why I made the mistake with the prefrontals and toes. At the Aurornis node the prefrontal may or may not be present. In any case in Aurornis it may be a vestige and one of the splinters around the skull. Dealing with crushed and overlapping material is difficult no matter the data source. During the process of identification and reconstruction mistakes can and do happen. That’s part of the process. Thank you for noting them.

      At the same time, and despite your access to the specimen, your Aurornis paper provided only a quick sketch tracing of the easy skull parts when all the bones were present. I wanted to learn more about the remainder of the skull so I found palatal and occipital bones that you either overlooked or ignored. Here are a few other notes.

      I reconstructed the manus slightly different than you did, but recognize that crushed manual digit 3 is difficult to interpret. I don’t agree that metatarsals 3 and 4 were fused as you indicate in the SuppData. That would be quite odd. Metatarsal 5 is also present in Archaeopteryx as a vestige, so I would be surprised if it was not present in Aurornis, as it appears. You wrote there are no scleral plates, yet you identified two. I’m sure you know, where you find two you’ll find a least a dozen. They are there and perhaps this is one of those instances were using a tool, like a computer monitor able to colorize and segregate one bone from another, may be better at pulling from the chaos difficult bones that were originally overlooked.

      Thank you for noting metatarsal 5 in Balaur, bound as it is, to metatarsal 4. I had access to and traced another image that shows a now unidentified bone distinct from anything I had seen in theropods. That it was odd and did not match the other view should have alerted me to a problem, but it did not sink in until your note.

      My tracing technique also helps to colorize the difficult and broken bone elements in their entirety. Those colors can help create a reconstruction (missing in your paper) by simply shifting the colors to their in vivo positions. Spot colors aid immensely in understanding the outlines of the bones. Colors can indicate little bone corners largely hidden beneath other bones. Colors can also identify bone splinters where present. By contrast, in your bone photographs, a pinpoint line in the middle of a bone tells us nothing about the outline of that bone, especially important when the bone is broke or at an odd angle. By this comment I am trying to encourage all paleontologists to adopt ‘best practices.’

      Keep those comments coming, Dr. Cau. Each one improves the product.

      Best regards ~

  2. Dave wrote:
    “As you know, working from photographs of two-dimensional specimens has proven time and again to be equal to first hand observation and superior whenever sufficient resolution is present and the tracer puts in greater effort. Many paleontologists use photographs and trace bone shapes, especially if the specimen appears chaotic.”

    This is ludicrous and blatantly self-serving. I can’t couch that in polite tone at the moment, so I will leave it to that.

    Scientists, ones describing fossils, do not describe them from photographs, but the actual fossils themselves. They have at their disposal magnifying lenses, microscopes, and the experience of having prepared the material or the data on its preparation — and the ability to tell preparation marks from non. In the rare chance only photographs of fossils are used, the caveat is always explicit that these are from photographs and therefore inferior to direct examination.

    NO SCIENTIST WILL EVER TELL YOU TO USE A PHOTOGRAPH BECAUSE ITS “JUST AS GOOD” AS THE REAL THING.

    If you have the real thing, you will use it first, foremost, and lastmost. Photographs are for presentation and a graphical display of an idea, never for the purpose of description. When you accuse Dr. Cau of “blackwashing” you, you do so while ignoring the last four years of your “whitewashing” your own mistakes, such as the excessive “plumage” of fossil lizards and various archosauromorphan sauropsidans. Cau describes directly the differences between your photograph-based observations and his in-person direct examination, and your ONLY RECOURSE is to effectively call him a liar. This is the existential crisis we’ve come to. The sad thing is, we’ve gone so far down this rabbit hole, I doubt you could tell your Walrus from your Carpenter. Meanwhile, scientists working with the original materials at hand are able to better address these concerns (both Drs. Marjanovič and Bennett have done this for you, and you’ve tossed them off; you refuse to accept any testing unless it comports with your established beliefs, and have the temerity to accuse others of bias).

  3. “By this comment I am trying to encourage all paleontologists to adopt ‘best practices.’”

    Then please, please, please – stop trying to work from photographs as though it’s as good as looking at actual specimens. Because it isn’t. Really. Full stop.

    I have been working with fossils for more than 20 years. I have, in the past, relied on high-quality photographs when specimens were not available. Some were two-dimensional fossils, others not – but regardless, the total number of specimens I coded from photographs and did NOT have to recode when I finally saw the real thing is zero.

    I continue at times to rely on photos, but always try to follow up with a collections visit to see the genuine article – not because I’m being some sort of elitist snob, but because extensive personal experience has shown that “working from photographs of two-dimensional specimens has proven time and again to be equal to first hand observation and superior whenever sufficient resolution is present and the tracer puts in greater effort” is patently untrue.

    I do try to encourage my students to adopt best practices. This is why I would never, under any circumstances, accept a thesis based on photographs.

    • Chris, all your points are well taken. I, too, go to the source whenever possible. However, I’m working with new levels of taxon inclusion that have not been attempted before in reptiles and getting novel results. Having now some 700+ taxa in my trees the possibility of visiting one and all is vanishingly small. It’s just not going to happen. Moreover, the vast majority of my data comes from uncontroversial data. What I’m offering colleagues are possibilities in taxon inclusion that they should explore. If my data is wrong, my results must also be wrong. Please send me a pair of taxa from my trees that should not nest together and tell me where the errant one should nest.

  4. David, your persistence does you no credit. I have lost track of the number of professional paleontologists I have seen tell you, “Your entire technique is unreliable and cannot be trusted to any degree,” only to have you ask them to do your work for you by reporting specific errors which you will then “correct” as though doing so magically erases the invalidity of the rest of the “data.”

    (The arrogance of your statement, “Keep those comments coming, Dr. Cau. Each one improves the product,” is jaw-dropping.)

    You have an idee fixe and are carrying out pseudoscience. Until and unless you stop, you will never have the credibility you so desperately seek. “They laughed at Galileo, they laughed at Einstein… but they also laughed at Bozo the Clown.” To use your own term (which only you use, to make all criticism of you sound unfounded), one cannot “blackwash” what is already black.

  5. You (whoever you are) are also welcome to tell me which two nestings are incorrect in the large reptile tree. One, a dozen or a hundred mistakes does not destroy a tree of this size or invalidate other unrelated interpretations. Especially after corrections are made.

    So, do you apply the same harsh judgement to the Cau team who did not find a fibula and fused two metatarsals together in Aurornis? See, it goes both ways. Or does it?

    Everyone, and I mean everyone, makes mistakes even with the fossil under their nose. I find it fascinating that the negative responses increase when corrections are made after better data comes in. You know that I change things when better data comes in. You -want- me to change things when better data comes in. So, why is that not applauded?

    The persistence comes from the data results, btw.

    • I’ve mentioned who I am before, though it may have been deleted along with several of my comments. My name is Mark Bradford, I live in Colorado, and my interest in paleontology is life-long but not professional — my scientific training is in astrophysics. (Which, ironically, is so heavily dependent on photography, because that’s the only way information about distant objects can reach us. But much more was learned about lunar geology from sample return than from remote sensing.)

      And you again persist in believing that correcting specific identified errors in your tree does something to validate the rest of your “data”, when you have been told repeatedly by professionals that it does not. YOUR UNDERLYING METHOD IS UNSOUND. It is not that “we”, or I, want you to make specific corrections in your tree. It is that we want you to recognize that your photographic data *are not superior to* data collected from the actual physical fossils. Yet when Andrea Cau pointed out a number of very specific flaws in your interpretation, your reaction to some of them is, “No, I’m right after all.”

      If you want to be applauded, do things worthy of applause. Your artwork is outstanding and has always been highly regarded and praised. If you could accept the urging of professional paleontologists to stop asserting the supremacy of photographs, and above all to stop behaving as though you have the only true answers and everybody else is wrong, you could still make valuable contributions to the field. You should be thrilled that professionals are taking their time to interact with you to the extent that they do, and take their advice to heart.

  6. Mr. Peters,
    Metatarsals III and IV are not fused and we did not write anything about intermetatarsal fusion in the paper or in the Supplementary Information: simply, the metatarsus is so crushed that the two bones cannot be distinguished. The “mt III + IV” label in the SI figure simply means that this part of the metatarsus shows the two crushed bones but they cannot be easily distinguished each other even by microscope. It is wise to NOT add information to a drawing if it cannot be properly checked in the actual specimen, so we avoided drawing fake boundaries among bones or fake bones due to paraedolia.

    I strongly encourage you to follow the same wise approach.

    For the same reason, the fibula cannot be distinguished from the collapsed tibial shaft, so we avoided to draw it in the picture. What you colored as the proximal part of your “fibula” is the proximal lateral condyle of the tibia and the fibular crest along the tibial lateral surface. Under microscope they are clearly visible as part of the tibia, with no boundaries. Your claimed boundary between tibia and fibula in that part of the leg is just the shadow of the fibular crest on the collapsed shaft due to the light angle of that photo shot.
    The other “fibular bones” outside the leg in your drawing are just the production of your fantasy which sees shadows in a roughly pixelled photo of a slab and decides they are a crushed displaced fibula.

    At this point, I have to conclude that if I send you two photos of the same leg done under different illumination angles you will see different bones with different shapes. That’s a funny art game, but no science at all.

  7. Good to know. Thank you for your comments, Andrea. Similarly in Cosesaurus a simple rotation of the specimen to change the lighting makes the entire humerus disappear. These things happen, but I see that as no reason to disparage the work of others.

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