What is Jianchangnathus?

A recent paper by Cheng et al. (2012) introduced a new basal pterosaur, Jianchangnathus robustus (IVPP V 16866). Middle Jurassic in age, Jianchangnathus shared several characters with Scaphognathus from the Late Jurassic, according to the authors. It was also compared to Fenhuangopterus, a basal dorygnathid from the same deposits at Jianchangnathus.

Jianchangnathus

Figure 1. Jianchangnathus was allied with Scaphognathus, but retains many traits of its ancestors within Dorygnathus.

A Basal Nesting in the Second Half of the Pterosauria
Here Jianchangnathus nested at the base of the Scaphognathia, essentially the second half of the Pterosauria. In this important phylogenetic site Jianchangnathus was derived from a sister to the Donau specimen of Dorygnathus, itself at the very base of the Dorygnathia and not far from Sordes, the outgroup taxon (Fig. 2). Pterorhynchus and the wukongopterids (= darwinopterids) were sister taxa.

A phylogenetic sequence that includes Jianchangnathus

Figure 2. A phylogenetic sequence that includes Jianchangnathus at the transition point between a basal Dorygnathus and Pterorhynchus + Scaphognathus. All are to scale. This is a rare instance of morphological transition in which a tiny pterosaur did not intervene.

Jianchangnathus was not originally subjected to a phylogenetic analysis, nor was it reconstructed.

The skull of Jianchangnathus with bones identified using the DGS method.

Figure 3. The skull of Jianchangnathus with bones identified using the DGS method. Here the nasal is in pink (anteriorly) and purple (posterior to the break).

Redescription Using DGS
Cheng et al. (2012) reported fusion between the premaxilla and maxilla. Here (Fig. 3) the suture is between the 4th and 5th tooth as in sister taxa. The first fang was the first maxillary tooth, as in the SMNS 55886 specimen of Dorygnathus. The dentary did not extend to the quadrate but extended posteriorly beneath posterior jugal as in sister taxa. The nasal extended to mid orbit as in sister taxa. The jugal extended to the pmx/mx suture as in sister taxa. The prefrontals were longer than originally reported. The vomers, ectopalatine and pterygoid were rod-like elements, as in sister taxa. The tip of the mandible is a double-tooth morphology.

Dorygnathus Was Barely Mentioned
The upturned premaxilla and anteriorly-oriented teeth are traits of Dorygnathus, but that taxon was not mentioned by Cheng et al. (2012) in comparison. The relatively large skull is a trait shared with Pterorhynchus and the wukongopterids. The manual and pedal element proportions are shared with sister taxa.

Maturity
Cheng et al. (2012) observed the non-fusion of the scapula and coracoid and mistakenly considered Jianchangnathus immature. In this case fusion, or a lack thereof, is a matter of phylogeny, not ontogeny. Because pterosaurs are lizards that do not follow archosaur growth patterns as discussed earlier. Sister taxa likewise do not fuse the scapula and coracoid and Jianchangnathus was similar in size to them (Fig. 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
Cheng X, Wang X-L, Jiang S-X and Kellner AWA 2012. A new scaphognathid pterosaur from western Liaoning, China. Historical Biology iFirst article available online 29 Nov 2011, 1-11. doi:10.1080/08912963.2011.635423

wiki/Jianchangnathus

3 thoughts on “What is Jianchangnathus?

  1. I am very interested in the Digital Graphic Segregation method. Do you mind tell me what software you use and how to do that. Thank you in advance.

    • Thanks for your interest. The DGS method works best with 2-dimensional fossils, but can be applied to lateral, dorsal, ventral views of all fossils. There are several examples of this in ReptileEvolution.com. (www.ReptileEvolution.com/cosesaurus.htm is a fine example). Essentially you take an undistorted (no fisheye lens!) photograph of your fossil, scan it to your computer, open the image in Adobe Photoshop or any similar graphic program. Add a layer to your image. Modify that layer to MULTIPLY. Then start coloring in the bones. If you’re working with a skull, whether articulated or not, color each element. Soon you’ll find all of the easy elements are colorized leaving some parts not colorized. By segregating those loose ends you may see that some continue on both sides of an overlying bone. These you may wish to add to a third Photoshop layer in order to segregate them from the others. Once all the bones are colorized and accounted for, you may select each color, copy it, then open a new file to paste your selection into. In this way you can assemble the parts into a reconstruction without distortion. The parts should all fit, of course. I hope this helps. Contact me if you have any trouble or wish further assistance.

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