Daurlong: crests or no crests?

Cau continues:
“1. The dorsal part of Daurlong’s skull has undergone an erosion of the external surface: this is evident from the analysis with UV rays, which shows a low fluorescence of the dorsal part of the skull compared to the ventral one. The degree of fluorescence of the bones is related to the preservation of the original external surface (more fluorescence = better preservation). The crest is devoid of fluorescence, resulting in deteriorated and eroded bone on the surface. This is also confirmed by sampling of bone material and by electron microscopy analysis.”

The difference is also apparent in white light. Is the crest an artifact of preparation? An unwanted artistic addition? Cau notes only the right ‘crest’ is devoid of fluorescence. If so, why does the left lacrimal rise to the same height? See DGS tracing in figure 2.

“2. The anterior part of the nasal region, at the level of the articulation with the premaxilla, is damaged and missing. It can’t be deduced from the photos, but there is a bony “step” between the “ridge” and the tip of the muzzle, that is, a piece of the lateral part of the premaxilla is missing, the one that articulates with the nasal. This indicates that the original joint between the two bones is missing.”

Again, was novel matter added to this fossil to improve its appeal and price?
That’s what we want to know.

Otherwise, tetrapod nasals usually appear in pairs. One or both can leave impressions in the matrix. Are these data dismissed by Cau? Not sure why the pmx-na suture is relevant to the present discussion (But wait! See below).

“3. Another dromaeosaurid from the Jehol Biota, Zhenyuanlong, shows a marked dislocation of the nasals and lacrimals with respect to the rest of the skull: [see Fig 1] this dislocation, evident from the way the specimen is fossilized, produces an “extreme” version of the crest of Daurlong.

As noted above, Cau misidentified the nasal and dorsal arch of the maxilla in Zhenyuanlong (Fig 1). So his example is less convincing than it should be. This is why DGS colors are so important. If you have a leftover bone or two after coloring the easy bones, then get back in there. Those splints and chips need to be colored, too.

“3. Continued… That is, the nasal of the Daurlong specimen is clearly at an early stage in the dislocation process which is more advanced in the Zhenyuanlong specimen.

Now I’m confused. Is the crest “at an early stage in the dislocation”
or is it an added artifact that is “devoid of fluorescence.”
Cau indicates both are true (perhaps this is a Google translation error).

“3. Continued. The most parsimonious explanation that we get from these elements is that the “ridge” of Daurlong is only the roof of the nasal (and part of the right lacrimal) which partially dislocated dorsally during the decomposition of the carcass. Originally, the roof of the nasal was flat, without ridges.”

Just to back up a bit… We were discussing the right lacrimal ‘crest’. Now Cau turns the argument to the anterior nasal ‘ridge’. Cau reports, “the roof of the nasal was flat.” That is correct. Everyone agrees. That not what we’re wondering about. We are interested in the cresting lacrimals (Fig 2). That vague published outline is intriguing and frustrating. More detailed tracings – and reconstructions based precisely on those tracings, please. No freehand impressions. Stick to the data.

Lacrimal crests are not scored in the LRT. These two taxa (Figs 1, 2) are not dromaeosaurids when the taxon inclusion set is expanded, as it is in the LRT.
Toe two is not a killer claw. The pubis was not retroverted.