The New Dendrorhynchoides Skull Revealed by DGS

Lü and Hone (2012) just published on a new Chinese anurognathid (Middle Jurassic, formerly GLGMV 0002, now JZMP-04-07-3) which they attributed to the genus, Dendrorhynchoides curvidentatus, but assigned a new species, D. mutoudengensis.

Tracing of the insitu specimen attributed to Dendrorhynchoides mutoudengensis by Lu and Hone (2012).

Figure 1. Tracing of the insitu specimen attributed to Dendrorhynchoides mutoudengensis by Lu and Hone (2012). Note the skull is encircled in a dashed line as few to no details and some vague basicranial materials are delineated. Some bones are only impressions in the fossil. Note the fourth wing phalanx which continues buried in the matrix a wee bit further. Note Lu and Hone 2012 only found one small finger. DGS found all three (figs. 2, 3), plus more vertebrae and enough of the skull (fig. 4) to make a reconstruction (fig. 5). The fibula on both legs are parallel to the tibia, not disarticulated. What looks like a disarticulated fibula is more likely m4.4, the last long wing phalanx.

Using First Hand Observations
Lü and Hone (2012) produced an in situ tracing (Fig. 1) with little effort or attention paid to the skull, which they admit is probably complete, just difficult to interpret. Unfortunately, it’s quite common for pterosaur workers nowadays to provide only the broadest, almost cartoony, outlines of specimens, foregoing the rigorous tracings that might reveal extra details (such as the described teeth). We saw this earlier with Jeholopterus and Dendrohrynchoides. Lü and Hone (2012) had the fossil in front of them, presumably with microscopes, etc. for the best possible resolution and detail and, by their own admission, they failed to deliver the sort of detail that would have made this a much better study.

No reconstruction
Moreover, reconstructions are rarely offered and they were not provided in Lü and Hone 2012. Reconstructions, like restoring an automobile after a car crash, are a great way to help figure out how the bones go back together in the original pterosaur. After all, it’s easier to tell make and model on the showroom floor than on the highway after an encounter with an 18-wheeler.

Using DGS (Digital Graphic Segregation)
Unfairly maligned, DGS is a technique whereby a flat fossil like this, can be photographed (or brought into Photoshop from the PDF file in this case), and enlarged on the monitor to provide an excellent wide screen microscopic view and a platform for tracing elements whether in outline or as colored shapes. A limit on resolution is the only issue. These tracings can then be lifted, as is, and placed into reconstructions, minimizing transfer errors. With the figures from the PDF I was able to trace more elements (Figs. 2-4). I asked for higher resolution photos and anticipate being able to draw out even more data when (if ever) those arrive.

Dendrorhynchoides new tracing

Figure 2. Using DGS, a new tracing of the specimen reveals more details. Closeups of the hand and skull are in figures 3 and 4. Most ribs and all gastralia were not traced here. Compare elements to figure 5, the reconstruction. Not sure what those white parallel “bones” are on either side of the tail, unless they represent a white substrate layer.

Dendrorhynchoides hand traced using DGS. Figure 3. Dendrorhynchoides hand traced using DGS. Also shown are two basipterygoids, a basisphenoid, a postorbital and squamosal. All three fingers are identified here.

Tracing and colorizing of skull elements in the new Dendrorhynchoides.

Figure 4. Tracing and colorizing of skull elements in the new Dendrorhynchoides in ventral view. Also traced are those unusual “toothy” elements anterior to the skull, which likely represent gouge marks made by the preparator, or seeds of some sort of plant. I am stymied otherwise. Dark yellow elements are palatines and ectopterygoids. Light red elements are pterygoids. Purple is a frontal. Orange is a nasal. Light green is a premaxillary ascending process. Red elements are quadrates. Yellow element is a basicranium. Blue elements are left lateral skull and mandible parts. Outlines indicate a mandible and the right lateral skull in medial view. See the reconstruction in figure 5 to see how it all goes back together. The skull extends to the in situ unguals, so Lü and Hone underestimated the length of the skull, which turns out to be longer than wide.

What Lü and Hone (2012) had to say
“The skull is crushed flat and little detail can be reconstructed or identified.” Figure 4 indicates otherwise. I only wish these professional pterosaurologists would have put a little more effort into making these observations and not leave it to the amateurs.

“Numerous small and splint-like palatal elements (as described by Bennett 2007a, and also seen in other specimens, e.g. Batachognathus) are visible on the surface (suggesting that the specimen is preserved in ventral view, but their exact identities cannot be easily determined.” It is clear from this description that the authors have no idea what the palate of an anurognathid should look like, but are following false paradigm based on a misinterpretation that goes back to studies on Batrachognathus. Ironically, those splint-like palatal elements are the only parts I was not able to find. They should appear at the base of the maxillary ascending process and may still be present intertwined in those proximal elements. It will take more resolution to find them. What Lü and Hone (2012) do see that are splint-like are the pterygoids and portions of the ventral mandible.

“…much of the pre-sacral vertebral column…appears to be missing entirely.” A sinuous and, at times, disarticulated string of vertebrae of appropriate size and numbers was found using DGS.

“The specimen appears to represent a juvenile animal… Elements that typically fuse in adult pterosaurs (e.g. the wrist, sacrum, scapula and coracoid) are here unfused.” Lü and Hone (2012) fail to note that in most to all anurognathids, these elements are unfused. So, the phylogenetic evidence indicates that anurognathids grew to adulthood without fusion, as we see in several clades and grades of pterosaurs, all phylogenetically isolated. Overlooked or ignored by Lü and Hone (2012), pterosaurs follow lepidosaur, rather than archosaur, growth strategies, as reported by Maisano (2002) in which adults may or may not fused certain bone sets.

“The scapula is nearly twice the length of the coracoid.” But their figure indicates the two are subequal. My tracings indicate the scapula was a little longer.

In their Figure 4, Lü and Hone (2012) use four arrows (two red and two yellow) to point to four teeth and palatal elements without identifying which arrows are pointing to teeth (probably the anterior one) and which to palatal elements (probably the posterior three). Interestingly the teeth appear on the base of the palatine, near its articulation with the pterygoid. That would be a first for pterosaurs, so a closer look is warranted.

The rest of their description was well done.

Validation and correction
As part two of DGS, the elements and tracings are validated by putting the elements back together into a reconstruction to check fit and identification (Fig. 5). Looks like everything fits in logical order, matching what we know of other anurognathid pterosaurs.

Reconstruction of the new Dendrorhynchoides mutoudengensis

Figure 5. Reconstruction of the new Dendrorhynchoides mutoudengensis. Everything fits and it looks like your standard anurognathid. The palatine articulates at the base of the ascending process of the maxilla and the ectopterygoid articulates at the mx/ju suture.

There is nothing odd about the new anurognathid in reconstruction. It looks like all of the others, with a large antorbital fenestra and eyes largely in the back half of its skull, as opposed to the current darling of traditional pterosaurologists, Bennett’s little monster. Phylogenetic analysis (details in tomorrow’s post) indicates this specimen is closer to, but not congeneric with, the flat-head anurognathid, rather than the holotype of Dendrohynchoides (contra Lü and Hone 2012). So, this pterosaur will someday need a new generic name.

My offer still stands
I continue to offer my services to any paleontologist having trouble deciphering a ‘road kill’ fossil. I also offer my reptile and pterosaur trees to help nest new specimens. Unfortunately, too often I’m put into the position of having to chastise paleontologists afterwards for poor workmanship or overlooked data, and that can be remedied.

Mistakes are forgivable. Not even trying to glean data is not.

We will discuss and make comparisons to the holotype tomorrow in part 2.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Bennett SC 2007a. A second specimen of the pterosaur Anurognathus ammoni. Paläontologische Zeitschrift 81(4):376-398.
Lü J and Hone DWE 2012. A New Chinese Anurognathid Pterosaur and the Evolution of Pterosaurian Tail Lengths (pages 1317–1325)
DOI: 10.1111/1755-6724.12002
Maisano JA 2002. Terminal fusions of skeletal elements as indicators of maturity in squamates. Journal of Vertebrate Paleontology 22:268-275.

1 thought on “The New Dendrorhynchoides Skull Revealed by DGS

  1. Pingback: DinoAstur - » Una nueva especie de Dendrorhynchoides (Pterosauria) del Jurásico Medio de China

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