Review History


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Summary

  • The initial submission of this article was received on November 13th, 2014 and was peer-reviewed by 2 reviewers and the Academic Editor.
  • The Academic Editor made their initial decision on December 6th, 2014.
  • The first revision was submitted on February 5th, 2015 and was reviewed by the Academic Editor.
  • A further revision was submitted on March 30th, 2015 and was reviewed by the Academic Editor.
  • A further revision was submitted on March 31st, 2015 and was reviewed by the Academic Editor.
  • The article was Accepted by the Academic Editor on March 31st, 2015.

Version 0.4 (accepted)

· · Academic Editor

Accept

Dear authors,

Considering that I have no other major concerns about text and figure performance, I am pleased to confirm that your paper “The first occurrence of the enigmatic archosauriform Crosbysaurus Heckert 2004 from the Chinle Formation of southern Utah " has been accepted for publication in PeerJ. I have marked just a minor changes that I will send directly to the PeerJ staff.

Thank you for submitting your work to this journal.

With kind regards,
Graciela Piñeiro

Version 0.3

· · Academic Editor

Minor Revisions

Dear authors,

I am glad to see how much the manuscript has been improved. Thus, it is almost ready to be accepted for publication in PeerJ. However, I suggested some minor changes to the text that you can see at the edited Word version that I am attaching to this letter. Besides, references must be modified as following the style of the journal. I fixed just some of the first references; you can follow the following examples for to complete the list:

Gottmann-Quesada A, Sander PM. 2009. A redescription of the early archosauromorph
Protorosaurus speneri Meyer, 1832 and its phylogenetic relationships. Palaeontographica
Abteilung 287:123–220.
Ottone EG,Monti M,Marsicano CA, de la Fuente MS, Naipauer M, Armstrong R,Mancuso AC.
2014. A new Late Triassic age for the Puesto Viejo Group (San Rafael depocenter, Argentina):
SHRIMP U–Pb zircon dating and biostratigraphic correlations across southern Gondwana.
Journal of South American Earth Sciences 56:186–199 DOI 10.1016/j.jsames.2014.08.008.
Piñeiro G, Ferigolo J, Ribeiro AM, Spindler F,Meneghel M, Ramos A. 2013. The first record of
sphenacodontid synapsids from Gondwana. In: XXIII Congresso Brasileiro de Paleontologia,
Gramado, Brazil. 265.
Gower DJ, Sennikov AG. 2000. Early archosaurs from Russia. In: Benton MJ, Kurochkin IN,
Shishkin MA, Unwin DM, eds. The age of dinosaurs in russia and mongolia. Cambridge:
Cambridge University Press, 140–159.

Please, you must to provide figure captions! I do not remember seeing them before.

After you have fixed all this, please submit just the corrected manuscript (including figure captions) following my suggestions, as I have already approved the figures.

Finally, please note that comments and corrections from UP are from me, your handling editor, so, you do not have to acknowledge an anonymous reviewer.

I hope you can do the requested changes and submit very soon.

Very best wishes,
Graciela Piñeiro

Version 0.2

· · Academic Editor

Major Revisions

Dear authors,
The manuscript has been improved with the inclusion of the reviewer suggestions. However, there are some weaknesses that can be fixed:

1. You should provide a better identification of the site from where the described tooth comes. A very simple map (as Figure 1) showing the geographical position of the outcrops relative to an important city or a geographic accident will be fine.
2. You should provide better pictures of the tooth, where its entire surface is in focus (please, see the annotated PDF file, that will follow).
3. Improve Figure 3 by adding some lithological information to the caption (e.g, describe the lithological arrangement at the different sections A, B, and C).
4. Improve the text by follow the recommendations in the Edited Manuscript file (which will be provided to you).
5. Once you have all these items fixed, please resubmit the manuscript for revision.

Best regards,
Dr. Graciela Piñeiro

Version 0.1 (original submission)

· · Academic Editor

Major Revisions

Two reviewers have now commented on your paper. Both found the material interesting, and agreed with the interpretation and the taxonomic assignment of the material. However both the reviewers consider that you should provide more precise stratigraphic information and improve the use of dental nomenclature and descriptions.
One of the reviewers recommended some changes to improve the figures that should be applied.

Please submit a list of changes or a rebuttal against each comment and recommendation made by the reviewers, which will be taken into account when you submit the revised manuscript.

·

Basic reporting

The authors describe a new fossil specimen based on a single, shed tooth crown from the Late Triassic of southern Utah. The authors refer this specimen to the enigmatic genus Crosbysaurus based on an autapomorphic character that only occurs in this taxon among Triassic archosauromorphs (Heckert, 2004). The specimen is well figured and rather well described, but some parts of the description should be improved.
The manuscript is generally well-written and figured, but I have several comments that the authors must address before its resubmission.
1) Dental anatomical terminology: the authors use a reptilian skeletal anatomical terminology, but they should use a dental terminology, i.e. “mesial” instead of “anterior”, “distal” instead of “posterior”, “labial” instead of “lateral, and “lingual” instead of “medial.”
2) Distribution of serrated crowns in Archosauromorpha: the authors follow Irmis et al. (2007) in the interpretation of Crosbysaurus as an indeterminate archosauriform. This interpretation is mainly based on the presence of denticles in the tooth crown, which was supposed to be an archosauriform diagnostic feature (Dilkes, 1998; Nesbitt, 2011). However, the recent description of Azendohsaurus as a non-archosauriform archosauromorph has proved the presence of denticles among more basal archosauromorphs (Flynn et al., 2010). As a result, I think that Crosbysaurus cannot be diagnosed unambiguously beyond an indeterminate archosauromorph and the authors should consider and discuss this possibility in the text.
3) The authors must provide a list of type specimens and locality/horizons in Systematic Paleontology.
4) Quotations in the main text are not homogenous, sometimes they have a comma and others don’t. The authors should homogenize them following the guidelines of the journal.
5) The authors describe the new specimen as distally curved. However, I can’t see a distal curvature of the crown as preserved, and the morphology resembles the crowns with straight distal margins of Crosbysaurus. I think that the curved region described by the authors is a broken/weathered margin. If it is the case, the authors should modify the discussion about the two morphotype of Crosbysaurus in the discussion. Beyond the curvature of the crown, the new specimen possesses differences with previously published teeth of Crosbysaurus and the rest of the discussion provided by the authors is well supported.
6) The authors should provide more information about the mesial margin of the crown. Can provide further details in the description to answer the following questions: does the portion of the margin basal to the ridge completely lack denticles? do the preserved denticles possess accessory serrations?
7) It is rather difficult to figure out the portions of the crown that are broken off or weathered down (see comment 5). I strongly suggest drawing an outline of the supposed complete silhouette of the crown based on other Crosbysaurus specimen and superposed on it the new specimen. In that way it could be discerned in the figure which margins of the apex are natural and which ones are broken.

The occurrence of Crosbysaurus in southern Utah is novel and its implications for regional biostratigraphy and for the Triassic of North America as a whole are interesting and deserve publication if the seven points outlined above are addressed satisfactorily. In addition, I attached a PDF of the manuscript with minor comments that the authors should also consider. As a result, I consider that the manuscript deserves publication in PeerJ after major revisions.

Experimental design

The collection and study protocols are well described and follow standard paleontological procedures.

Validity of the findings

The taxonomic assignment of the new specimen is well supported.

·

Basic reporting

Generally the article is adequately written—one weak point is the stratigraphy—the authors really should be able to indicate the stratigraphic level of the fossil horizon more precisely, and discussing (or at least mentioning relevant units) of other Crosbysaurus occurrences. From Figure 2 it looks like they are either in the lower Petrified Forest Formation (I would call it Blue Mesa Member) or else in the Monitor Butte Formation---can they at least say how high above the base or Shinarump Formation the locality is?

The authors also need to adapt tooth nomenclature—I advocate using mesial, distal, labial, lingual, and occlusal. Smith & Dodson (2003) is worth consulting, as is, perhaps, a classic such as Farlow et al. (1991).

Smith, J.B. and Dodson, P., 2003. A proposal for a standard terminology of anatomical notation and orientation in fossil vertebrate dentitions. Journal of Vertebrate Paleontology, 23(1): 1-12.

Farlow, J.O., Brinkman, D., Abler, W.L. and Currie, P.J., 1991. Size, shape, and serration density of theropod dinosaur lateral teeth. Modern Geology, 16: 161-198.

Experimental design

The design is adequate, but the authors need to (1) expand their comparisons and (2) use more explicit terminology.

RE: (1) There are other teeth with compound denticles from the Chinle both named (e.g., Lucianosaurus, Hunt and Lucas, 1994, in biblio) and unnamed (see Butler et al., 2006, for example, for Owl Rock Fm teeth originally described by Kirby in his thesis), as well as Kryzyzanowskisaurus, which is distinct from Revueltosaurus callenderi (e.g., Heckert, 2005, in article biblio already). The authors need to make that comparison as well as include some statements at the beginning of the "differential diagnosis" to indicate that only taxa with oblique, subdivided denticles need be compared (basically flesh out "most described Triassic tooth taxa" to indicate that these teeth are different from most archosauriform teeth.

RE: (2) Throughout I think the authors should look at Heckert (2004) and Irmis et al. (2007) and make sure that they are using very similar, highly specific language in their comparisons.

Butler, R. J., Porro, L. B., and Heckert, A. B., 2006 A supposed heterodontosaurid tooth from the Rhaetian of Switzerland and a reassessment of the European Late Triassic record of Ornithischia (Dinosauria): Neues Jahrbuch für Geologie und Paläontologie Monatshefte, v. 2006(10), p. 613-633.

Validity of the findings

I think the authors are correct—this tooth fragment probably should be referred to Crosbysaurus. Hopefully they have recovered more from the locality as additional, more complete material would certainly cement the importance of the paper.

I do think that the more convex side of the tooth is labial and the flatter side lingual.

Comments for the author

I think Figure 3 would benefit form sketches of the teeth (outline drawings, similar to Heckert, 2004). I like Fig. 4, but outlines of 3A and 3B would help two, with the right alignment figs 2 and 4 could be combined, this would also help offset the blurry nature of parts of 3A and 3B. The key morphology is clear, but parts of the tooth are out-of focus.

Also, check the NM map in Figure 1B—I think you have the star in the wrong place for the NM Crosbysaurus specimens (from Zuni Mountains).

Also, we identified Crosbysaurus sp. in North Carolina (Heckert et al., 2012), so I would amend the caption of Figure 1 to read "Crosbysaurus localities (yellow) in the southwestern U.S.A. Note that Crosbysaurus needs to be italicized in the figure caption.

Heckert, A.B., Mitchell, J.S., Schneider, V.P. and Olsen, P.E., 2012. Diverse new microvertebrate assemblage from the Upper Triassic Cumnock Formation, Sanford subbasin, North Carolina, USA. Journal of Paleontology, 86(2): 368-390.

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