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[# PeerJ Staff Note - this decision was reviewed and approved by Laura Wilson, a PeerJ Section Editor covering this Section #]
Much improved after revision.
The paper was greatly improved during revision and can be published.
MS is greatly enhanced with much more robust citation of prior work, comparisons with other material, etc.
As before, this seems ok.
Conclusions seem much more plausible in this version, and the speculatory bits are now more reasonable.
Overall, this is much improved. I especially appreciate the 3D models and the revised figures.
The description is well-done and most of the figures are good. A major problem are the unwarranted hints of diplodocoid affinities of at least some of the bones. There is no solid phylogenetic argument here and, unless this point is properly addressed by a phylogenetic analysis, the manuscript cannot be accepted.
Review of „New titanosauriform (Dinosauria: Sauropoda ) specimens from the Upper Cretaceous Daijiaping Formation of southern China” by Fenglu Han, Xing Xu, Corwin Sullivan, Leqing Huang, Yu Guo, and Rui Wu
The paper describes sauropod bones from the Upper Cretaceous Daijiaping Formation of Tianyuan County, Zhuzhou City, Hunan Province, southern China. The bones belong to different individuals and possible different species as they come from several stratigraphic levels. All specimens are referred to Titanosauriformes indet. I see the only one serious problem in the paper, the misinterpretation of the cervical vertebra ZG T002 (Fig. 3). The lateral pleurocoels described are not on the centrum but on the neural arch. Consequently, all comparisons of these structures are incorrect. The vertebra is broken just posterior to the posterior end of diapophysis. Comparing with cervicals of Erketu, more than half of the centrum might be missing (not only small part as authors believed). On the centrum there is one elongated pleurocoel which is incomplete posteriorly. Another pleurocoel could be on the missing part of the centrum. The ischium indeed has some similarities with that bone in rebacchiosaurids. As it is an important specimen, a 3d model of the ischium is desirable.
Line 156: Add Titanosauriformes indet. On a new line after Titanosauriformes Salgado, Coria and Calvo, 1997.
Lines 168-169: Change “both an anterior and a posterior pleurocoel” to “both anterior and posterior pleurocoels”.
Lines 168-169: “On the less distorted left side, both an anterior and a posterior pleurocoel are completely preserved, suggesting that only a small portion of the centrum is missing posteriorly”. The vertebra is missing all the centrum posterior to the diapophysis. Compared with the vertebrae in Erketu, more than half of the centrum is missing, not only “a small portion”. The pleurocoels described are on the neural arch, not on the centrum (see below).
Lines 172-173. “However, the relatively anteroposteriorly short and dorsoventrally tall centrum suggests that the vertebra may be an anterior or a posterior cervical”. You cannot decide how the vertebra was long anteroposteriorly because it is incomplete posteriorly. This incompleteness may cause illusion that the centrum is short.
Figure 3A. It is said to be the left lateral view, but appears to be ventrolateral view. Please indicate the position of the diaphysis.
Figure 3D. The lamina labelled as PODL is SPOL, not PODL.
Lines 181-183: “The low and transversely narrow neural spine is another indication that the vertebra is an anterior cervical, as in Euhelopus the neural spines become transversely wide and bifurcated posterior to cervical 11”. Do you mean neural arch? Neural spine is missing on this specimen.
Lines 187-188: “The lateral surface of the centrum is excavated by two shallow pleurocoels, one anterior and one posterior, which are separated by a prominent, posterodorsally oriented ridge (ppr, Fig. 3A)”. The “ppr” ridge is on the neural arch, not on the centrum. Consequently both described pleurocoels are also not on the centrum. Indication of parapophysis and diapophysis on this neural arch would help orientation of the vertebra.
Lines 213-214: “The dorsal surface of the parapophysis is excavated by a large pneumatic fossa (Fig. 3G)”. No paparpophysis or pneumatic fossa on it are visible on Fig. 3G.
Lines 217-218: “The anterior part of the ventral surface of the centrum bears three adjacent large fossae, whereas the posterior part bears a prominent midline keel”. This the middle part of the centrum, its posterior part is missing.
Lines 244-245: “The keel essentially divides the posterior part of the ventral surface into two large, shallow depressions”. Again, this is a middle part of the cervical centrum, the posterior part is missing.
Line 345. In Mamenchisaurus only anterior caudal centra are procoelous.
Lines 352-355. There is no need to mention absence of the pneumatic fossa on the middle caudal centrum. This fossa is present in anterior caudals of very few sauropods. A similar longitudinal ridge on the centrum is present in middle caudals of basal titanosaur Andesaurus.
Description of ischium. Did collateral ischia contacted along the midline? Please describe and add illustration of ischium in ventral view.
Lines 589-590: “However, the analysis in question did not include the earliest titanosaurian from Asia (Tapuiasaurus).” Tapuiasaurus is from South America. Do you mean Tengrisaurus?
Figure 6. Please label iliac and pubic peduncles. A 3d model of ischium would be helpful.
The material was adequately figured (mostly), but I’d like to see figure 3 broken up. As it is, it’s too busy and the elements are very small within it. I’m also not thrilled with Figure 6 – I’d like to see some more views of the entire specimen. But generally I appreciate that there are many views of the elements.
Conclusions not supported by data:
Everything is fine, up until the authors introduce the idea that there might be Cretaceous diplodocoids in Asia. Allow me to be perfectly honest: there might have been, but you don’t have them. The strongest character you have tying the clade to your material is the ventral keel on the cervical centrum, and by your own admission this is a) plesiomorphic b) widespread and c) morphologically distinct from the character in dipolodocoids (lines 229-231). Beyond that, a proportional character of the ischial shaft (which, again, is also known in titanosauriforms) is your only other evidence, which I don’t find compelling, particularly given the enormity of the claim. On the other hand, the broken edges of your material display large open cells, an unambiguous synapomorphy of Titanosauriformes (which you discuss starting with line 262). To even entertain that this material is non-titanosauriform in nature relies on a willingness to ignore essentially everything we know about your material, the sauropod faunas of Cretaceous China, and neosauropod evolution.
From a descriptive point of view, I think this paper is fine. The material, while not excellent, has clearly been gone over in detail by the authors and thoroughly mined for anatomical detail. While not necessarily the order I would have chosen, the descriptions clearly follow a path around the material that the reader is able to follow with little difficulty. If the paper were to be just this, I would give it a thumbs up. However, the authors append what I can only describe as a “hook” – something to spice up an otherwise run of the mill description – but in this case I think they have missed the mark.
Ultimately, I can’t see a way forward to publication as long as the speculation about diplodocoid ties to the material remains – it’s just not supported in any way by what you have. Excise that in its entirety and you’re left with a solid (if unspectacular) description of some potentially novel sauropod material, and there’s nothing wrong with that.
Line 541: Diplodocoids did survive into the Late Cretaceous – not very long, and it doesn’t seem to have been many taxa, but they were there.
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