Eosinopteryx – part 3 – to scale

Updated November 5, 2015 with a new interpretation of the pectorals,a new nesting and images of Eosinopteryx and Xiaotingia

Sometimes it just helps
to see taxa to scale with possible sisters (Eosinopteryx in this case, Fig. 1). Smaller than Aurornis, Eosinopteryx also had a shorter snout, shorter torso, shorter tail, more robust clavicle and shorter pubis.

Figure 1. Eosinopteryx and kin, including Xiaotingia, Aurornis and Archaeopteryx (Thermopolis).

Figure 1. Eosinopteryx and kin, including Xiaotingia, Aurornis and Archaeopteryx (Thermopolis).

Godefroit et al. (2013) reported, “The straight and closely aligned ulna-radius of Eosinopteryx also means that pronation/supination of the manus with respect to the upper arm would have been limited; combined with the absence of a bony sternum and weakly developed proximal humerus, these attributes suggest that Eosinopteryx had little or no ability to oscillate the arms to produce a wing beat.”

Funny that they didn’t even mention the short coracoid.
The locked down elongate coracoid is a hallmark of flapping tetrapods (pterosaurs and birds) and an elongate clavicle does the same thing in bats.

The ulna is not bowed
in Aurornis or Eosinopteryx. It is bowed in Xiaotinigia and Archaeopteryx and more greatly bowed in subsequent flapping taxa, including oviraptorids by convergence. The coracoid is strut-like and locked down to the sternum in Xiaotingia and Archaeopteryx, perhaps by convergence because overall Archaeopteryx has proportions more similar to Aurornis.

Figure 2. Xiaotingia is an outgroup taxon to basal birds. The left coracoid is broken and reconstructed here. The coracoid should be as deep as the furcula. The coracoid is longer here than in Eosinopteryx implying a greater ability to flap.

Figure 2. Xiaotingia is an outgroup taxon to basal birds. The left coracoid is broken and reconstructed here. The coracoid should be as deep as the furcula. The coracoid is longer here than in Eosinopteryx implying a greater ability to flap.

The bowed antebrachium
produces a parallelogram in living birds that serves to automatically extend and fold the manus bearing the outer flight feathers with flexion/extension of the elbow. Prior to this, muscle power would have to extend and bend the wrist, independent of the flexion/extension of the elbow.

References
Godefroit P, Demuynck H, Dyke G, Hu D, Escuillié FO and Claeys P. 2013. Reduced plumage and flight ability of a new Jurassic paravian theropod from China. Nature Communications 4: 1394. doi:10.1038/ncomms2389

wiki/Eosinopteryx

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3 thoughts on “Eosinopteryx – part 3 – to scale

  1. Minor nitpick- your picture has the typo Archaeornis instead of Anchiornis. Also why do you use Huaxiagnathus as an example of something close to a paravian ancestor? Oviraptorosaurs are the sister to paravians, so Protarchaeopteryx or Caudipteryx would be better, or Falcarius a bit further out, or Haplocheirus, or Shenzhousaurus, or even Ornitholestes. I have good references for all of these, if you need them (though I cringe imagining your reconstruction of Protarchaeopteryx’s crushed skull)

    More importantly, Xiaotingia does not have coracoids like that. Such elongate and straight coracoids wouldn’t be expected until Ornithothoraces (enantiornithines and more derived birds). And indeed, a high resolution photo shows the distal end of the upper one is just a slightly discolored area of rock, just like the discolored area in front of the scapula- http://s4.postimage.org/c0w22glel/Xiaopect.jpg . The lower one doesn’t even exist- http://upload.wikimedia.org/wikipedia/commons/1/11/Xiaotingia.jpg . So that’s another failure of your application of DGS.

    How many more will it take for you to agree your tracings shouldn’t be trusted? From my end, it seems like there’s no number of times I could show errors that would lead you to question your general accuracy. It’s as if you had a cladistic analysis, which I questioned the coding accuracy of. I look at one character, show it’s wrongly coded. I look at another, and show it is. Five more, ten more. To your credit, you correct them, but surely I don’t have to look at every single character and check its accuracy separately before I’m justified in saying your coding is flawed in general and should not be trusted? The fact that when you move into taxa I know, I instantly see tons of problems makes me very concerned about your interpretations of taxa I’m unfamiliar with.

  2. Point by point:
    1. Thank you for the typo alert. Now fixed.
    2. Those other taxa are derived toward their respetive clades. Huaxiagnathus appears to be more plesiomorphic.
    3. Discolored and raised areas of rock are great places to go digging for bone. That’s where the coracoids are IMHO. The top little uncolored bone (Fig. 2) between the scap and coracoid is a flake off the coracoid. What is going on beneath the humerus is going to have to remain one of those mysteries, but it is clear that the coracoid is beneath it. The nesting of Eosinopteryx and Xiaotingia are suspect due to the presence or lack thereof of the bowed ulna and elongated coracoids, which are red flags here signaling, perhaps, another look at the tree topology. If I’m wrong, I’m wrong. This can be settled by a little digging.
    4. I thank you for all your valid corrections. Have those corrections shifted tree topology? No. Your argue that if one to ten mistakes are found then the whole method is flawed, yet you use the same method to show my flaws. Evidently it works, so where is the logic in that? I said when I created this creature that I was somewhat at a loss when it came to birdy reptiles, but that the short coracoid was important. A key ingredient in DGS is experience, which was lacking on my part but is slowly gaining. Your instruction was valuable, and I thank you for it. But for you to say that nothing of mine should be trusted is not scientific. Mickey, go with what you know. Get the rest later. Don’t anticipate. That would be the definition of prejudicial. I do not say that everything Hone and Witton do is wrong just because I disagree with many things they promote. No, I take one problem at a time. Godefroit et al. (2013) did not note the posterior mandible in their drawing, they reported an autapomorphic lacrimal and did not see the mandibular fenestra, yet I hear no similar accusations from you against them. Makes me wonder what the motivation is here.

    And to your point about making mistakes. I find mistakes ALL THE TIME in my work when I restudy it while adding new taxa. You have no idea how many hundreds of mistakes I have found in the history of these trees. Even so, and this is amazing to me, the tree topologies remain essentially unchanged, swamped by all the correct data — plus the corrections strongly tend to cement rather than separate established relationships. Yes, it can go that way too.

    We’re all learning as we go.

  3. Pingback: DinoAstur - » Un nuevo dinosaurio emplumado del Jurásico: Eosinopteryx

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