New Material of Karakoromys (Ctenodactylidae, Rodentia) from Late Eocene-Early Oligocene of Ulantatal (Nei Mongol): Taxonomy, Diversity, and Response to Climatic Change

Round 1

Reviewer 1 Report

This is a good study, a bit narrow as only one group of rodents is considered - but this makes the story clear and supports the interpretation.  The turnover in this group seems clear and calls for explanation of what factors drove it - the authors perceive abiotic drivers - probably precipitation.

Authors say that Euryodontomys is close to Karakoromys - okay, but they should say simply how these are related (same subfamily?) and whether any other related genera occur there.  Otherwise, why consider Euryo?

Authors clearly say how their species differ, but they should briefly say how they distinguished them in a mixed sample.  For example, the sample at 30 m: okay, chelkaris is small, but are the others easily distinguished? By the way, I did not see that body mass was discussed later, although invoked in section 3.5.  This study is novel and important in that it examines successive biotic samples for changes in relative abundance of species - that is just the sort of study that should be done!

I attach a pdf with edits - both bits deleted and suggested other terms - plus a couple of comments.

Comments for author File: Comments.pdf

English is really very good and the authors are to be commended for their efforts.  I do include what I hope are improvements on the pdf.

Author Response

Dear reviewer:

We are very grateful to you for your careful revisions and helpful suggestions. We have made revisions and responses based on your feedback and suggestions. For specific revisions, please download the main text, and the following is a brief response. 

Point 1: Authors say that Euryodontomys is close to Karakoromys - okay, but they should say simply how these are related (same subfamily?) and whether any other related genera occur there.  Otherwise, why consider Euryo?

Response 1: We have briefly added a description of the relationship between Euryodontomys and Karakoromys and the reasons for choosing Euryodontomys. Please see Line 137-144 in the revised manuscript (Under the "Track Changes" function in Microsoft Word)

 

Point 2: Authors clearly say how their species differ, but they should briefly say how they distinguished them in a mixed sample.  For example, the sample at 30 m: okay, chelkaris is small, but are the others easily distinguished?

Response 2: Firstly, most of the specimens were collected independently from scattered fossil sites, and the samples were not extensively mixed, even though they were of the same layer. In addition, although these four species have very similar overall morphology, they have stable distinguishing features that enable us to easily distinguish them. However, in order to make it easier for readers to grasp their differences, we have added the most prominent distinguishing features of these species in the genus remarks. (Please see Line 234-243)

 

Point 3: By the way, I did not see that body mass was discussed later, although invoked in section 3.5. 

Response 3: Thank you for pointing out this issue. Anyway, we did not discuss body mass in the following text. In fact, this article is not intended to reconstruct precise body mass, but only to use molar size to examine the potential body size change and ecological shift in Karakoromys-Euryodontomys lineage. To reduce misunderstandings, we have removed the introduction of body mass (size) from the materials and methods, and only retained the necessary tooth size analysis in the discussion section. (Please see Line 154-157; 897-903)

We have accepted most of your suggestions regarding words and expressions, except for a few where we have made our own adjustments or maintained the original expressions.

Line 13: Response: We have made minor modifications. (Please see Line 13)

 

Line 380-381: What do you call these?

Response: We are confident that these two molars do not belong to Karakoromys, but preliminary identification suggests that these two molars do not match well with other members of the superfamily Ctenodactyloidea. Thanks to your reminder, we have added a sentence “Accurate classification of these two specimens require further research in the future”.

Line 419: Response: We think original expression ” Small ctenodactylid.” is more accurate in expressing what we mean.

Line 475: Response: It is a key identification feature of Karakormys whether the posterior arm of protoconid has a lingual end. We think original expression is more accurate in expressing what we mean.

Author Response File: Author Response.docx

Reviewer 2 Report

Xu and colleagues describe new material of ctenodactylid rodents, limited to the genus Karakoromys, from the Late Eocene-Early Oligocene Ulantatal, providing taxonomic attributions, diversity analyses, and discussion in relation to climate change.

 

The manuscript represents a valid and detailed contribution for specialists of the group as well as being of potential interest for a wider audience, in the framework of the climatic and environmental changes of the Eocene–Oligocene transition. Therefore, I think it perfectly fits the scope of the journal in general and the special issue in particular.

 

The figures are also nice and clear, but In Figure 3: the indication “mm” is missing in some cases. Anyway, I suggest removing any reference to mm in the graphs and adding “measurements in mm” or equivalent expressions in the caption.

 

I have some further comments I ask the authors to consider when revising the manuscript.

 

The authors should add in materials and methods information on the software package(s) used for the analyses.

 

Similarly, they should provide information on how box plots are constructed (whiskers length, quartiles approximation, outliers…).

 

Further, a concise description of the Cluster analysis used and the rationale for choosing it are needed, rather than a simple citation.

 

I recommend providing the complete set of measurements collected in supplementary materials, for transparency and replicability. This is especially relevant as the authors stated that “All data generated during this study are included in this published article” in the appropriate section, while they are not.

 

Line 137: reference to “body mass” is confusing here, as if anticipating estimates. Whether M2 and m2 measurements are in the same relationship with the real body mass of the animal and what kind of relation exists (isometric, allometric, etc.) is not easy to say. Simply “size” would be better.

 

The authors should be consistent in the use of lower or uppercase for certain terms, like early Oligocene or Early Oligocene. Check everything.

 

Other things are listed below:

 

In the title: stata? perhaps strata?

 

Line 39: rodent group.

 

Line 45: but not limited to.

 

Line 49: from Lower Oligocene deposits (or strata, or sites).

 

Line 141: this sentence is unclear. I suggest, “Kakaromys has long been considered to include only one species…”

 

Line 462: here and elsewhere, better spell out in full names after punctuation.

 

Line 465: “Significance at at P ≤0.05α” check and correct.

 

Lines 776-777: … but without providing GPS coordinates or detailed stratigraphic information…

 

Line 912: in line with the Court Jester hypothesis.

 

Line 915: as predicted by the Red Queen hypothesis.

 

Line 925: Karakoromys is not in italics.

 

In the supplementary doc: Scale Bar not in uppercase.

The text is well-written, although it would benefit from a careful proofread, especially in the description. I annotated below some typos/confusing sentences, but I invite the authors to check the entire manuscript carefully.

Author Response

Dear reviewer:

We are very grateful to you for your careful revisions and helpful suggestions. We have made revisions and responses based on your feedback and suggestions. For specific revisions, please download the main text, and the following is a brief response.

 

 Point 1: In Figure 3: the indication “mm” is missing in some cases. Anyway, I suggest removing any reference to mm in the graphs and adding “measurements in mm” or equivalent expressions in the caption.

Response 1: We have modified Figure 3 according to your suggestion and added measurement unit in the caption. Please see Line 513 and Line 522 in the revised manuscript (Under the "Track Changes" function in Microsoft Word)

 

Point 2: The authors should add in materials and methods information on the software package(s) used for the analyses.

Response 2: We have added information on the softwares used for the analyses in Materials and Methods. (Please see Line 129, 130, 153)

 

Point 3: Similarly, they should provide information on how box plots are constructed (whiskers length, quartiles approximation, outliers…).

Response 3: We have added information on how box plots are constructed in the caption of Figure 3. (Please see Line 517-521)

 

Point 4: Further, a concise description of the Cluster analysis used and the rationale for choosing it are needed, rather than a simple citation.

Response 4: We have briefly introduced the cluster analysis (CONISS) method and its applicability. (Please see Line 151-153)

 

Point 5: I recommend providing the complete set of measurements collected in supplementary materials, for transparency and replicability. This is especially relevant as the authors stated that “All data generated during this study are included in this published article” in the appropriate section, while they are not.

Response 5: We will add the complete measurement dataset in the Supplementary materials according to your suggestion.

 

Point 6: Line 137: reference to “body mass” is confusing here, as if anticipating estimates. Whether M2 and m2 measurements are in the same relationship with the real body mass of the animal and what kind of relation exists (isometric, allometric, etc.) is not easy to say. Simply “size” would be better.

Response 6: this article is not intended to reconstruct precise body mass, but only to use molar size to examine the potential body size change and ecological shift in Karakoromys-Euryodontomys lineage. To reduce misunderstandings, we have removed the introduction of body mass (size) from the materials and methods, and only retained the necessary tooth size analysis in the discussion section. (Please see Line 154-157; 897-903 )

 

Point 7: The authors should be consistent in the use of lower or uppercase for certain terms, like early Oligocene or Early Oligocene. Check everything.

Response 7: We have unified the entire text into uppercase letters, such as Late Eocene, Early Oligocene.

 

Point 8: In the title: stata? perhaps strata?

Response 8: I'm sorry for the spelling error caused by my carelessness. I have deleted the word 'stata'. (Please see Line 3)

 

 

We have accepted all of your suggestions regarding words and expressions.

Author Response File: Author Response.docx

Reviewer 3 Report

Overall the paper is well written.  There are a number of very minor issues with the English.  For example the use of the word occlusal instead of occluded is often used although the later word is used correctly towards the end of the paper.  This may be more of an automatic spell check issue than anything else.  Please see my attached file in which I have listed by line suggestions regarding the English.  These should be able to quickly addressed.  In many cases these are just typos.

The science is good, but I noticed that for some taxa there is a discussion of the root pattern but not for all.  As the root pattern seems to be important in some taxa, in order to be consistent, it should be described/discussed for all the taxa, especially if it is considered an important character which is used to distinguish relationships.  In the attached document, other similar issues are described so should be easy to address by the authors.

This paper will be publishable once these minor issues are addressed.

Comments for author File: Comments.pdf

Please see my notes on the English at the beginning of the previous comments and suggestions for authors.

Author Response

Dear reviewer:

We are very grateful to you for your careful revisions and helpful suggestions. We have made revisions and responses based on your feedback and suggestions. For specific revisions, please download the attached document, and the following is a brief response.

 

Point 1: I noticed that for some taxa there is a discussion of the root pattern but not for all. As the root pattern seems to be important in some taxa, in order to be consistent, it should be described/discussed for all the taxa, especially if it is considered an important character which is used to distinguish relationships.

Response 1: We have added a description of root pattern for all taxa, listed in the first paragraph of each species' description. Please see Line 278-282; 421-422; 560-561; 711-712 in the revised manuscript (Under the "Track Changes" function in Microsoft Word)

 

Point 2: Title: is stata supposed to be strata?

Response 2: I'm sorry for the spelling error caused by my carelessness. I have deleted the word 'stata'. (Please see Line 3)

 

We have accepted most of your suggestions regarding words and expressions, except for a few where we have made our own adjustments or maintained the original wording.

 

Line 18: suggest it read … based on the rich accumulation of fossils…

Response: For the sake of sentence conciseness, we believe that the original expression may be better. (Please see Line 18)

 

Line 181: metaloph and hypocone absent to present, then to developed, longitudinal I am not sure what, then to developed, or what it refers to. Please clarify.

Response: Our original intention is that the connection between the metaloph and the hypocone goes from absent to present and then to well-developed. To reduce ambiguity, we have deleted the phrase “then to developed”. (Please see Line 197)

 

Line 190: absent, and the absent. Not sure what and the absent means or to what if refers, please clarify.

Response: Our original intention is that hyposinusid is usually reduced or absent, and the absence of hyposinusid will result in continuous ridge fused by hypoconid and hypoconulid. We have made modifications to its expression to make the sentence meaning clearer. (Please see Line 206)

 

Line 415: Is there any indication for the presence of a DP3 in K. arcanus? It is mentioned for K. decessus, so mentioning whether a DP3 is or is not present in this species should be addressed.

Response: We have added relevant descriptions based on the DP3 of the type specimen. (Please see Line 456)

Author Response File: Author Response.docx