Dear Mr Ijouiher,
thanks for making this MS available as a Preprint.
This MS is an interesting piece of work, especially because a comprehensive review of the Bahariya fauna allows for comparisons across the faunas in Norther Africa in the Cretaeous.
Having published on Sigilmassasaurus, I have looked through the section of this MS that deals with theropods, and have found some issues. It would be great if these could be addressed toward the final submission.
As the MS does not have any line numbers, I have to refer only vaguely to paragraphs and sentences within the "Dinosauria" section of the paper.
Only one sentence of the Dinosauria section deals with Spinosaurus aegyptiacus itself. I think this section should be expanded to briefly review the material found by Stomer, and its destruction during WWII. It would be worth noting that detailled German desctricptions, alongside drawings and few photographs of the original material exists, but that new material from Morocco referred to the same taxon has been named the neotype by Ibrahim et al. (014), even if other workers disagree with this taxonomic identification and thus the validity of the neotype designation (Evers et al. 2015).
The species epithet "braviolis" is repeatedly used throughout the MS for Sigilmassasaurus. However, the correct species name is Sigilmassasaurus brevicollis (see Russel, 1996). This should be corrected.
This comment refers to this paragraph of the MS: "While Sigilmassasaurus braviolis [sic] (Russell, 1996) is usually considered a junior synonym of Spinosaurus (Evers et al. 2012; McFeeters et al. 2013; Ibrahim et al. 2014b), it now appears that S. braviolis [sic] may indeed be a valid taxa (Evers et al. 2015)"
It is incorrect that Evers et al. 2012 or McFeeters et al. 2013 consider Sigilmassasaurus a junior synonym of Spinosaurus. Evers et al. 2012 find spinosaurid affinities for Sigilmassasaurus, and McFeeters et al. 2013 interpret Sigilmassasaurus as a valid basal tetanuran taxon. Evers et al. 2015 agree with McFeeters et al. 2013 on the validity issue, but present evidence for spinosaurid affinities. Therefore, the paragraph could be changed to something like:
'While Sigilmassasaurus brevicollis (Russell, 1996) has been considered a junior synonym of Spinosaurus (Ibrahim et al. 2014b), it now appears that S. brevicollis may indeed be a valid taxon (McFeeters et al. 2013; Evers et al. 2015).'
Evers et al. 2015 are cited in several instances, but this citation is not present in the reference list. It should be included.
Correct citation is : Evers SW, Rauhut OWM, Milner AC, McFeeters B, Allain R. (2015), A reappraisal of the morphology and systematic position of the theropod dinosaur Sigilmassasaurus from the “middle” Cretaceous of Morocco. PeerJ 3:e1323; DOI 10.7717/peerj.1323
In the sentence "While accepting the argument that there are two separate spinosaurids in North Africa, Cau (2015) questions whether this material is truly distinct from Spinosaurus (in which case Sigilmassasaurus braviolis [sic] would become Spinosaurus braviolis [sic]).", Cau (2015) is cited, but this is not listed in the reference section.
In the sentence "While such a discussion is beyond the scope of this paper; all that matters herein is that there were clearly two distinct spinosaurids in this region (Russell 1996, Evers et al. 2015), irrespective of whether they are separate on a species level or genus level.", another paper could be cited, which is Hendrickx et al. 2016. These authors also accept two spinosaurids in the Cenomanian of Morocco, and present evidence from quadrate bones that is independent of the data presented by Evers et al. 2015.
Suggested citation: Hendrickx C, Mateus O, Buffetaut E (2016) Morphofunctional Analysis of the Quadrate of Spinosauridae (Dinosauria: Theropoda) and the Presence of Spinosaurus and a Second Spinosaurine Taxon in the Cenomanian of North Africa. PLoS ONE 11(1): e0144695. doi:10.1371/journal.pone.0144695
The Sigilmassasaurus section of this MS should refer to Stromer's Spinosaurus B material. It should be noted that the material of Spinosaurus B is considered to represent Spinosaurus aegyptiacus by Ibrahim et al. (2014), but that Evers et al. (2015) list a number of anatomical differences between the original material of Spinosaurus B and the material found by Ibrahim et al. (2014).
If the author has further questions about my comments, please get in touch (my contact is available through the PeerJ paper).
This is a great start for a manuscript analyzing the palaeoecology of a famous fauna. My comments are meant to be constructive to make it even a better manuscript.
1. Lithostratigraphy - this should be expanded to discuss the lithology of formations. Currently, it does little other than give their names. Emphasis should be placed on the nonmarine members to give a sedimentological context to your interpretations of the nonmarine palaeoecology. The fact that there are three members recognized in the Bahariya Formation demonstrates at least three lithofacies representing different depositional environments. Each depositional environment is going to have hosted different palaeoecosystems. This is not a minor issue. Consider: if member X is marginal marine, then the dominant invertebrates and aquatic vertebrates are going to be marine. The presence of freshwater vertebrates or invertebrates is anomalous and either indicates organisms washed to sea or a brief freshwater incursion. If the latter, we would expect to find the fossils in a narrow, restricted zone. If the former, we would expect a more random distribution in the strata. If the overlying member Y is nonmarine, then the fossil organisms are going to reflect terrestrial and freshwater components of the paleoecosystem. Currently, the Bahariya Formation is treated as having a single, homogeneous fauna and flora – that I do not believe for the reasons given.
2. A "Bahariya mangrove" is frequently referred to by you and by others (frequently dinosaur paleontologists), but the supporting evidence is weak to non-existent. The term "mangrove" has a very specific ecological definition either involving a plant of the family Rhizophoraceae or in a broader sense of coastal vegetation that is tolerant of salt water flooding at high tide. I find it very telling that Lyon et al. (2001) in their abstract on the flora of Bahariya do not use the word, nor do they identify a rhizophoracean-like plant. Lyon et al. do refer to coastal vegetation, which does not imply mangrove-like habitat.
3. Finally, any palaeoecological interpretation of the Bahariya must look at the regional picture. Ibrahim et al. (2014) failed to do that when they proposed Spinosaurus swimming in giant rivers. First, there is no sedimentological evidence of north-flowing, large river system draining the heart of Africa during the Cenomanian. Creating one for Spinosaurus to swim in is like the creation in the late 1800s-1900s of giant lakes during the Late Jurassic for Morrison sauropods to stand neck-deep in. Second, Lyon et al. (2001) note that the leaf physiognomy indicates a dry and warm climate. Such an climatic interpretation for the low latitudes is supported by proxy sea surface temperatures (e.g., Schouten, S., Hopmans, E.C., Forster, A., van Breugel, Y., Kuypers, M.M. and Damsté, J.S.S., 2003. Extremely high sea-surface temperatures at low latitudes during the middle Cretaceous as revealed by archaeal membrane lipids. Geology, 31(12), pp.1069-1072), deep sea temperatures (e.g., Huber, B.T., Norris, R.D. and MacLeod, K.G., 2002. Deep-sea paleotemperature record of extreme warmth during the Cretaceous. Geology, 30(2), pp.123-126), and modeling (e.g., Hay, W.W. and Floegel, S., 2012. New thoughts about the Cretaceous climate and oceans. Earth-Science Reviews, 115(4), pp.262-272.). In other words, there is no paleoclimatic evidence supporting high rainfall conducive to the formation of giant rivers for Spinosaurus to swim in.
4. One possibility for the fluctuating sea level not discussed by you is a Milankovitch control. This has been discussed by a variety of authors (e.g., Gale, A.S., Hardenbol, J., Hathway, B., Kennedy, W.J., Young, J.R. and Phansalkar, V., 2002. Global correlation of Cenomanian (Upper Cretaceous) sequences: Evidence for Milankovitch control on sea level. Geology, 30(4), pp.291-294; Sageman, B.B., Rich, J., Arthur, M.A., Birchfield, G.E. and Dean, W.E., 1997. Evidence for Milankovitch periodicities in Cenomanian-Turonian lithologic and geochemical cycles, Western Interior USA. Journal of Sedimentary Research, 67(2).
There are other points that could be addressed, especially the ecological reconstruction that relies too much on supposition and assumptions because of inadequate fossil data (e.g., use of negative data to support rarity of ornithopods; taphonomic filters were not addressed by you). Nevertheless, this draft of the manuscript is a good start that could be improved by a more rigorous analysis and less speculation.
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