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Thank you for your work on this revision, particularly in the reorganization of the text in response to the reviewer and editorial comments.
[# PeerJ Staff Note - this decision was reviewed and approved by Kenneth De Baets, a PeerJ Section Editor covering this Section #]
In light of the significant revisions to an earlier version of the manuscript, I solicited a new review. The reviewer provided a thorough analysis of the work, with a variety of comments and suggestions. After looking at the previous reviews and decisions, as well as the current round of edits and review, I note some major themes to address:
1) The reviewer correctly notes that some aspects of the holotype description are limited in the current text -- for instance, the occipital region, palatal apertures, and otic notch could all use some additional attention (although I'll note that the otic notch *is* mentioned in the holotype description--but could use an extra sentence or two to describe shape, etc.). Please give strong consideration to bolstering these areas.
2) I empathize with both viewpoints on how the descriptive text for the crania can be organized, and also understand the drawbacks for each course of action (separate sections for each specimen, versus one combined element-by-element description across all specimens). I really do agree with the previous reviewers that the completely separate descriptions for each cranial specimen create redundancy as well as simultaneous gaps in the descriptions. I also agree with your decision to separate descriptions for holotype and referred material, in order to avoid confusion in future literature if any identifications are modified. The latest review suggests an elegant compromise solution -- "that each bone be described in the following ‘sections’: holotype material, complementary description, intraspecific variability." Although I recognize the rewriting required, I really do think it necessary to improve flow and usability for the reader. I'll note that the postcranial material is already effectively organized in this fashion, I suppose because none of it can be referred with 100% confidence. In any case, the suggested edits would help increase consistency between sections and improve readability, and should be made.
3) Is there any particular reason why YPM VPPU 021742 is not discussed in more detail? Is it under study elsewhere? Or was the issue that you were not able to examine it in person? Even if the latter case is the primary reason, I do think at least some additional comparison should be included as best you can from the photos, especially because a full figure is devoted to the fossil. How might it inform discussions of variation / similarity across B. bakeri?
4) The reviewer provides compelling reasons for including Almasaurus in the phylogenetic analysis, and this should be addressed one way or another in the revision.
5) I'll note that UMMP 14262 is addressed in detail in your document with a note on its presumed loss, so that precise comment does not need to be addressed (although the more general aspect of the comment #5 should be considered during revision).
The reviewer explains these and many other smaller suggestions in their longer review. Thank you for your close attention to these comments.
This manuscript provides a detailed reassessment of the long-neglected taxon “Metoposaurus” bakeri. As stressed by the authors, metoposaurids are a very abundant component of Late Triassic ecosystems, and their study is of strong interest to many researchers worldwide. As such, this reassessment and taxonomic revision is much welcome. Nevertheless, I have several issues with the manuscript that need to be addressed.
Before all, I must stress that I wholeheartedly agree with the methodological criticism and changes made by the authors to a previous study by myself and several colleagues. Our phylogenetical analysis should be considered as one of the first steps in our modern understanding of metoposaurid phylogeny, and all constructive criticism and modifications are much welcome. That being said, I have read the rebuttal letter answering comments from reviewer assessments prior to my own and I must thank the reviewers and editor for their integrity and professionalism in correcting the fashion in which our work was criticized. The text now seems adequately written to me. I stress this point here and intentionally sign this review to make it clear that I have no conflict of interest with the authors whatsoever.
See comments below.
No comment.
Description
I am aware that the authors have already argued against a comprehensive description of B. bakeri including information from all specimens in favor of separate descriptions. However, I agree with the editor that this was not an optimal choice for the following reasons:
1. The holotype is not well preserved and does not show all cranial diagnostic characters. I also feel its description is heterogenous, with a detailed palatal description, more concise skull roof description, and short assessment of the occiput (15 lines). Also, some parts (otic notch, all palatal apertures) are not described.
2. Some exquisite specimens (e.g. UMMP 13820, 13823) provide the opportunity for a reference work on metoposaurid anatomy, which could be further supplemented by the isolated material, as done for the mandible and postcranium. Yet, as the holotype is described first, all subsequent descriptions are very succinct and I don’t feel that they provide a clear picture of the anatomy of B. bakeri.
3. The authors provide a new interpretive drawing of YPM VPPU 021742 and refer to this specimen in the ‘comparative osteology’ section, yet this specimen is not described and hardly compared to the others.
4. This study would benefit from an assessment of the ontogenetic age of the specimens relative to each other. Ontogenetic variation indeed seems to be a recurrent problem in metoposaurid anatomy and taxonomy. There is probably no need for histological sections as the monotaxicity of the bonebed could allow for qualitative comments.
5. The in-depth work of the authors on vouchers and previously published specimens should be summarized in a dedicated section in the material and methods. In fact, some specimens are not described at all as it is (e.g. UMMP 14262).
6. The authors provide 2 arguments against a comprehensive description: that the attribution of some specimens is not unequivocal, and that it provides better linkage between the figures and text. I agree with the first point, but the second is purely stylistic and I do not consider it valid. I also do not think the material to be so abundant, nor the description to be so long (as comparisons are in a dedicated section) that this would be a problem.
In light of my previous comments, I highly suggest the addition of dedicated ‘material & voucher’ and ‘ontogeny’ sections and a complete reorganization of the description in a comprehensive one. However, I can understand the need for a clear description of the holotype for taxonomic reasons, and suggest that each bone be described in the following ‘sections’: holotype material, complementary description, intraspecific variability. This should satisfy both the authors and editor, and will result in a much shorter, less redundant and easier to read manuscript.
Phylogenetical methods
- The authors exclude Almasaurus from their new matrix, stating that some studies have regarded it as sister-group to metoposaurids, but that it may be closer to ‘small-bodied stereospondyls’ such as Rileymillerus, the latter of which has recently been recovered closer to brachyopoids than metoposaurids in a recent broad-scale study. They further state that no study has coded for both Almasaurus and ‘small-bodied stereospondyls’. This is incorrect as Sues and Schoch (2013) include brachyopoids, metoposaurids, Almasaurus and Rileymillerus and recover the latter three in a clade (see also Schoch, 2008, 2011 for somewhat similar ‘preferred’ topologies). Also, their first point is an over-simplification: to my knowledge, no study including both Almasaurus and metoposaurids has failed to recover an Almasaurs-metoposaurid clade or at least both taxa in a polytomy with others. Thus, I believe there is no ground to support the exclusion of Almasaurus, and I urge the authors to better argue or reconsider their decision.
- I don’t think the parameters used for the analyses of the new matrix under parsimony are explicitly stated (e.g. only character weights discussed line 245). It is my understanding that they differ somewhat from that of Buffa et al. (2019), at least in the treatment of multistate taxa, but this is not explicitly stated.
Phylogenetical results
- The tree presented in fig. 56B is not the strict consensus (which is identical to that of Fig. 56D) but is one of the two parsimonious trees.
- Although not figured, I think it is worth noting that the analyses do not recover Callistomordax as sister-group to metoposaurids.
- I agree that the incongruent topologies between all analyses, and the low support for all nodes hamper the discussion of the phylogeny of the group. Nevertheless, two clades could have been discussed further, namely Metoposauridae and the European Metoposaurus clade. While the surprising position of Callistomordax may explain why Metoposauridae is not discussed at this time, I feel like any characters recovered as synapomorphies of the European taxa are of interest for paleontologists and biostratigraphers, even if they are revised in the future.
Discussion
- Polymorphism: I cannot agree more on the need to include polymorphism in anatomical descriptions, which would be much facilitated in this study by a more comprehensive description. However, as it is common practice to score taxa in phylogenetic matrices based only on morphologically mature specimens (unless a juvenile is the only representative of a given taxon, and even then, with much caution), I must stress that only non-ontogenetic variability should be included in phylogenetical analyses. This is the main reason why I ask for an ontogenetic assessment section.
- Comparative osteology: Many of the characters summarized in the diagnosis of B. bakeri are not discussed here. I suggest either to further detail this section, or to include comparisons throughout a comprehensive description that could be summarized here.
- Ontogeny: This section is perfectly fine with me. However, I find it surprising that the role of ontogeny is discussed in some detail, but that there is no assessment of the ontogenetic maturity of the specimens described here. Also, as it is the smallest known referred specimen, I strongly suggest that the authors describe the anatomy of YPM VPPU 021742, as any variability would be of much anatomical and possibly systematic interest (my points 3 and 4 above).
Figures
- There seems to be a lot of white space on figs. 5, 30, 34, 39, 48 and 53.
- Fig. 3: “colors represent geographic regions”, please explicitly state which region each color represents.
- Fig. 5: abbreviations are missing for all palatal and occipital elements.
- Fig. 6: a lot of abbreviations should not be here.
- Fig. 7 was missing so I was unable to assess it.
- Fig. 8: there is no ‘fl’ captioned on the interpretive drawing.
- Fig. 10: ‘ptd’ is not indicated by a line in the interpretive drawing.
- Fig. 13: ‘pal’ is missing from abbreviations
- Fig. 14: subfigs E and F are missing so I was unable to assess them.
- Fig. 18: there are 2 subfigs f and no subfig G, and no mention of subfig K in the figure caption.
- Fig. 19: there is no subfig H and no mention of subfig G in the figure caption.
- Figs. 21-22: please indicate that the anterior direction is facing up as in previous figures.
- Fis. 23-24: I understand that there are right and left elements, please indicate which side the elements correspond to when possible.
- Figs. 31-33: I understand that the subfigs represent different views of specimens grouped under a single collection number, but that each group includes intercentra from various part of the column. I believe organizing the subfigs by vertebral column region would be more pertinent and would make for a much easier linkage with the text.
- Fig. 33: there is no mention of subfigs F-J in the figure caption.
- Figs. 35-37: similar comment to figs. 31-33, I would suggest reorganizing the subfigs following rib type rather than views.
- Fig. 49: what do views ‘1’ and ‘2’ mean?
Tables
- Table 1: UMMP 13055 has an asterisk and UMMP 13904 is bolded, please state why or correct this.
Bibliography
There are several discrepancies between the text and bibliography. For example, the authors cite Wiens, 1995, 1998, 1999, 2001 and Wiens et al., 2005 with only the latter included in the reference list. Please check all citations and references.
Minor line by line comments
- Line 222: change “Buffa et al.” for “Buffa, Jalil & Steyer, 2019” as used throughout the text.
- Line 367: please caption the lateral line canals on figs. 5-6 (and other relevant figures).
- Line 393-394: it looks like you say the alary process is likely absent in the holotype, bu this process is present in B. bakeri. Please reformulate.
- Line 411: I don’t think you can say what shape the nasal has on this specimen. “polygonal” sees more conservative than rectangular, and it is confirmed by more complete specimens.
- Lines 482-483: does the ornamentation extend on the cultriform process?
- Line 551-553: Please caption the foramen magnum and lamellose process on fig. 8.
- Line 584: Please caption the septomaxilla on fig. 9.
- Lines 588-596: It seems the shape of the prefrontal and the morphology of the lacrimal-jugal suture vary as well (because of the thinner lacrimal?). The supratemporal seems more pointed anteriorly as well. What do you think?
- Line 615: Please caption the nerve foramen on fig. 9.
- Line 642: Please caption the ectopterygoid on fig. 12.
- Lines 719-720: I do not see a second fragment on fig. 14C-D, does this refer to the missing subfigs E-F?
- Lines 752-753: Please explain what part of the skull is shown on subfigs A-B.
- Lines 781-811: This description is very hard to follow. Please refer to subfigs instead of fig. 16 as a whole for clarity, and provide a global account of the material under UMMP 14098, as done for many other specimens in the manuscript. Also, I strongly recommend adding captions for various structures on fig. 16 (stapes, pterygoid fragment, nerve foramen, etc.)
- Line 952 Please caption the postglenoid ridge on fig. 26.
- Lines 956-957: and what of the other canals in the posterior part of the mandible? Please caption those on fig. 26.
- Lines 1015-1026: see comment figs. 31-33.
- Lines 1093-115: This paragraph is very confusing as Case’s (1932) identification as a puboischium and that of the authors as a scapula require different orientations of this fragment. I suggest focusing more on the new interpretation, with short notes throughout the text to explain that a given margin was interpreted differently by Case.
- Line 1121: please caption the scapular crest on fig. 39.
- Line 1130: please caption de sensory groove on fig. 40.
- Lines 1180, 1186: please caption the supinator process and insertion of the m. biceps brachii.
- Lines 1192-1205: this comment is only based on ‘resemblance’ and should explicitly state morphological characters that support this re-identification.
- Line 1206: It seems like Case’s misidentification of the tibiae as ulnae explains why his tibia is in fact an ulna. While I don’t doubt this reidentification, morphological arguments are needed to support this.
- Lines 1213-1214: please caption the extensor keel and posterior ulnar keel on fig. 48.
- Lines 1218-1242: change first sentence for “previously identified as radii”, otherwise this is very confusing. I would also exchange this paragraph with the next (same for Fig 49 and 50) so the description of the autopodia comes after that of the radius.
- Lines 1243-1252: This paragraph shows little to no actual description of the radius.
- line 1245: change “that” for “the radius” for clarity.
- line 1249: the poplietal fossa is ventral and the tendinal fossa dorsal, not the other way around.
- Lines 1266, 1270: please caption the linea obliqua and acetabulum on fig. 51.
- Lines 1277-1305: please caption the intertrochanteric fossa, trochanter, adductor crest, poplietal fossa and intercondylar fossa on figs. 52-53.
- Lines 1310-1311: please caption the ‘shallow groove’ and fibular sulcus in fig. 54.
- Line 1316: how exactly are they different from A. browni?
- Lines 1318-1326: please caption the cnemial crest and through, and the cristae anterior tibiae on fig. 55.
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