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