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Reconstructing Cathayornis using DGS methodology
Cathayornis yandica (Zhou et al. 1992, Figs. 1-3, IVPP V9769) was an Early Cretaceous enantiornithine bird known from a virtually complete skeleton on plate and counter plate. It is crushed flat.
The best published tracings
of this specimen are shown here (Fig. 1). I wonder if you’ll agree there is too much left to the imagination in both of these professional tracings. The easy parts are correctly labeled, but I sense confusion in the more difficult details. Some of these were labeled originally with a “?”.
Figure 1. Previous best efforts at tracing Cathayornis. Above, Tracing of Cathayornis from Zhou et al. 1992. Below tracing of Cathayornis skull by O’Connor and Dyke 2010 traced using camera lucida. Some element labels are guesses (See “?”). A few are mistakes.
Try DGS just once to see if it works for you.
Applying color overlays to digital images of Cathayornis (Fig. 2, 3) recovers more bones more accurately than prior efforts (Fig. 1). And these can be used in reconstructions (Fig. 3). Note the postorbital and squamosal both drifted over the right frontal. That was a surprise. Yes, a tiny postfrontal is present, not fused to the frontal. Broken bones can be identified and repaired. Even the palatal bones can be identified.
Figure 2. Cathayornis skull animated GIF. Each frame lasts 5 seconds. Here virtually all skull elements are identified and applied to the reconstruction in three views (below). Compare the results of this technique to figure 1. Note how the upper and lower jaws match curves.
There is no guarantee you’re going to get things right the first time.
I don’t get things right the first time. I make changes as the interpretation runs its course. All DGS does is to remove some of the confusion inherent in the roadkill by segregating one bone after another until most – or all – of the bones are accounted for and fit the reconstruction while matching the patterns of sister taxa.
The postcrania
of Cathaysaurus is traced here (Fig. 3) and used to create a reconstruction in several views. The furcula can be traced here. Originally it was overlooked and misidentified.
Figure 3. Cathayornis tracing and reconstruction from tracing. Boxed area are ventral and rib elements originally segregated on a distinct layer and offset here for clarity. Note the green furcula, overlooked originally. Those green bones on either side of the sternum are considered part of the sternum in traditional works. Perhaps they are, but the visible one appears to overlay the sternum, rather than be a part of it.
It may just be a matter of applied effort
When you discover something in paleontology, all you have to do is unveil it. The discovery is the big deal. Not much effort is required, but it is always appreciated. Later workers can add details with appropriate levels of support and criticism. If I had access to the specimen or a higher resolution image, perhaps the level of accuracy would increase further.
Now I’ll ask of the bird people
what I ask of the pterosaur people. Try to build a reconstruction. It helps when you realize there are parts missing and then you can apply more effort to look for that part in the specimen itself.
If I have made any mistakes here, please bring them to my attention. I’m no bird expert, but I’m learning as I go. Here is a new image of enantiornithine birds to scale (Fig. 4) including Sulcavis, which we looked at recently.
Figure 4. Enanthiornithine birds to scale. Click to enlarge. Note: the deeper the coracoids, the deeper the pubis.
References
O’Connor J-K and Dyke G 2010. A Reassessment of Sinornis santensis and
Cathayornis yandica (Aves: Enantiornithes). Records of the Australian Museum 62: 7-20.
Zhou Z.-H, Fan F-J and Zhang J 1992. Preliminary report on a Mesozoic bird from Liaoning, China. Chinese Science Bulletin 37: 1365-1368.
Source: https://pterosaurheresies.wordpress.com/2015/10/23/reconstructing-cathayornis-using-dgs-methodology/
