Wulong: a new troodontid, not a microraptor-dromaeosaur

Poust et al. 2020
bring us news of a small, subadult theropod with some interesting traits, Wulong bohaiensis (Early Cretaceous; D2933). They considered the specimen a microraptorine dromaeosaurid.

Figure 1. Wulong in situ, plus the original published diagram.

Figure 1. Wulong in situ, plus the original published diagram. The specimen is somewhat surrounded by a few coprolites = cop.

By contrast, 
the large reptile tree (LRT, 1637+ taxa) nests Wulong among similar, small, long-legged troodontids, between Buitreraptor and Caihong. While this topology differs from that of other workers, the same can be said of nearly every clade in the LRT. That’s why this blog has been self-labeled ‘heretical’.

Figure 2. Wulong skull, original diagram, DGS colors applied to bones and reconstruction based on the DGS tracings.

Figure 2. Wulong skull, original diagram, DGS colors applied to bones and reconstruction based on the DGS tracings.

So, why the different views?
That appears to be due to taxon exclusion. There is no indication in the text that Buitreraptor and Caihong were included in analysisThere is no indication that the authors created a reconstruction, which helps identify bones, their ratios and proportion in crushed taxa like Wulong. More importantly…

Figure 4. Wukong manus DGS tracing and reconstruction. Note the 180º rotation of the manus relative to the radius and ulna.

Figure 4. Wukong manus DGS tracing and reconstruction. Note the 180º rotation of the manus relative to the radius and ulna.

… several taxa converge on birds
and small feathered theropods converge with each other in the LRT. The differences between the clades should not be determined by a few traits (= Pulling a Larry Martin), but here are gleaned after phylogenetic analysis of several hundred traits. As mentioned earlier, you can’t nest a specimen within a clade by a small number of cherry-picked traits because there is so much convergence within the Tetrapoda. Rather, run an analysis and find out which taxon is the last common ancestor of a derived clade. Those, then, are the validated clade members.

Figure 3. Wulong pelvis.

Figure 3. Wulong pelvis.

Figure 4. Wulong pedes, original tracing and reconstruction based on DGS tracings.

Figure 4. Wulong pedes, original tracing and reconstruction based on DGS tracings.

Uniquely
the coracoid is fenestrated in the middle. The ilium includes a prepubis process. Some feathers are preserved.

The authors report,
“Wulong is distinguished by several autapomorphic features and additionally, has many characteristics that distinguish it from its closest well-known relatives. Compared with Tianyuraptor and Zhenyuanlong, Wulong is small and its forelimbs are proportionally long.”

By contrast,
in the LRT Tianyuraptor and Zhenyuanlong are not related to troodontids, microraptorids or dromaoeosaurids. Tianyuraptor and Zhenyuanlong are basal to tyrannosaurids.

References
Poust AW, Gao C-L, Varricchio DJ, Wu J-L and Zhang F-J 2020. A new microraptorine theropod from the Jehol Biota and growth in early dromaeosaurids. The Anatomical Record. American Association for Anatomy. DOI: 10.1002/ar.24343

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