What is Yonghesuchus?

Updated August 18, 2019
with better data creating a better reconstruction. 

Yonghesuchus sangbiensis (Wu, Liu and Li 2001) was the first tetrapod discovered from the Late Triassic of China. The presence of pterygoid teeth was thought to preclude membership within the Archosauria despite a suite of traits to the contrary. Moreover Eoraptor and Turfanosuchus, both have palatal teeth — so it can happen. The specimen is known from a dorsally crushed skull (missing the skull roof) and a series of cervicals and their ribs.

Added August 18, 2019: better data helps to make a better reconstruction.

Added August 18, 2019: better data helps to make a better reconstruction.

The skull of Yonghesuchus in lateral and ventral view.

Figure 1. The skull of Yonghesuchus in lateral and ventral view. Elongated amphicoelus cervical vertebrae with ribs on elongated stems were similar to those in Dromicosuchus.

Earlier Nestings
Originally (Wu, Liu and Li 2001Yonghesuchus was thought to nest closer to Archosauria than either Proterochampsa and Turfanosuchus, (which are only distantly related to each other). A larger study was needed to resolve this matter.

Dilkes and Sues (2009) nested Yonghesuchus between Turfanosuchus and Archosauria (Gracilisuchus and Scleromochlus + Marasuchus). This is close to correct in that Yonghesuchus nests deep within the basal crocodylomorpha and two out of three of these were crocs.

Desojo et al. (2011) nested Yonghesuchus between Turfanosuchus + Doswellia and Scleromochlus + Marasuchus. Gracilisuchus was not far off. Clearly Doswellia does not belong in this group of bipeds and protobipeds. Adding more basal crocs would have clarified this issue.

Nesting in the Large Study
Here Yonghesuchus nests with Saltopus, a basal member of the Crocodylomorpha within the Archosauria. The low wide skull and relatively short skull roof versus jawline are two croc traits. The missing squamosal would have fit into the notch on the postorbital. The maxillary teeth were angled posteriorly. The antorbital fenestra was relatively large.


References
Desojo JB, Ezcurra MD and Schultz CL 2011. An unusual new archosauriform from the Middle–Late Triassic of southern Brazil and the monophyly of Doswelliidae. Zoological Journal of the Linnean Society, 2011, 161, 839–871. DOI: 10.1111/j.1096-3642.2010.00655.x
Dilkes D and Sues H-D 2009. Redescription and phylogenetic relationships of Doswellia kaltenbachi (Diapsida: Archosauriformes) from the Upper Triassic of Virginia. Journal of Vertebrate Paleontology 29(1):58-79
Wu X-C, Liu J and Li, J-L 2001. The anatomy of the first archosauriform (Diapsida) from the terrestrial Upper Triassic of China. Vertebrata PalAsiatica 39 (4): 251–265. online pdf.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.