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PLOS One

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Additional Editor Comments:

Dear authors,

After a complex search for reviewers, I agree with two of them that the submitted work is of very high quality and will undoubtedly be a very important contribution to the study of sigmodontines. According to both reviewers, only a few minor details need to be addressed before accepting your manuscript for publication. I apologize for the delay, but I am certain your wait will be well worth it.

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

Reviewer #1: Yes

Reviewer #2: Yes

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2. Has the statistical analysis been performed appropriately and rigorously? -->?>

Reviewer #1: Yes

Reviewer #2: No

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3. Have the authors made all data underlying the findings in their manuscript fully available??>

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.-->

Reviewer #1: Yes

Reviewer #2: Yes

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4. Is the manuscript presented in an intelligible fashion and written in standard English??>

Reviewer #1: Yes

Reviewer #2: Yes

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Reviewer #1: This manuscript presents the first discovery and documentation of Sigmodon minor from the early Blancan deposits of the San Miguel de Allende Basin (SMA), central Mexico, supported by radiometric age control ranging between 3.9 and 3.68 Ma. This represents a significant biochronological and paleobiogeographic contribution, extending the known range of S. minor well into southern North America and offering a new perspective on Blancan faunal exchanges.

The taxonomic identification is robust and well-supported through extensive morphological comparison with other Blancan and extant Sigmodon species. The conclusions regarding dispersal from the Great Plains and the paleoecological interpretation of open grassland-dominated habitats are consistent with the presented evidence and stratigraphic context.

The geological background and stratigraphic framework are well summarized, referencing both volcanic ash layers and associated index fossils (e.g., Nannippus peninsulatus, Glossotherium). These data provide solid age constraints and contextual support for the early Blancan assignment. The integration of radiometric and biostratigraphic data enhances the manuscript’s biochronological reliability.

The description of the maxillary and mandibular elements is detailed and precise, with clear specimen documentation (MPGJ series, UNAM collection). The authors provide adequate anatomical terminology and comparative analysis, which together justify the taxonomic identification of Sigmodon minor. The inclusion of both juvenile and adult morphotypes is particularly valuable for understanding intraspecific variation and ontogenetic trends.

However, a more quantitative component—such as plots or scatter diagrams of molar length vs. width—would significantly strengthen the analysis. This addition would illustrate variation across specimens and facilitate visual comparison with other Blancan populations (e.g., Meade Basin material). Even simple bivariate plots could reinforce the morphological conclusions already discussed in text form.

The paleobiogeographic synthesis is one of the manuscript’s strengths. The discussion effectively integrates Sigmodon minor occurrences across North America and identifies an asymmetrical dispersal pattern from the Great Plains toward both western and southern regions. Although largely qualitative, this discussion is well supported by the available data.

Typographical error at P25L425 (“Anterocone”) should be corrected.

This is a scientifically sound and significant paper, documenting an important southern occurrence of Sigmodon minor that enhances our understanding of Blancan rodent biogeography and early Pliocene faunal dynamics in North America. The study is technically solid, methodologically appropriate, and well contextualized within regional geology.

The manuscript will be ready for publication after these very minor refinements.

Reviewer #2: I have completed the review of the manuscript PONE-D-25-46840, entitled “First record of Sigmodon minor (Rodentia) in the early Blancan of central Mexico: asymmetrical dispersal from the Great Plains and paleoecology inferences”

This is a novel and valuable study, and I recommend it for publication in PLOS ONE. The authors present an important taxonomic, biogeographic, and paleoenvironmental analysis of cranio-dentary remains of the extinct cricetid rodent Sigmodon minor recovered from the early Blancan (Pliocene) of the San Miguel de Allende Basin, Guanajuato, Mexico. The morphological description of the fossil remains is of high quality. However, I have noted a few comments below, which I believe will help to improve the overall quality of the submission.

1. The authors propose that it is possible to distinguish between older and more recent populations of Sigmodon minor based on molar size, as this species appears to decrease in size over time or to be replaced by larger cotton rat species. However, no statistical analyses were conducted to evaluate size variation through time. I suggest applying a multivariate approach (e.g., principal component analysis).

2. The authors should provide details on the accumulation conditions. Specifically, how the microvertebrate remains were accumulated at the site (e.g., predation, in situ death, or reworking by post-depositional agents). Understanding the taphonomic history of the fossil assemblage, supported by robust evidence, is essential for interpreting paleoecological relationships and for refining paleoenvironmental reconstructions.

3. line 49: It should be clarified that the genus belongs to a sigmodontine cricetid, Sigmodon (Cricetidae, Sigmodontinae). Line 659: the genus name Sigmodon should be italicized.

4. Figure 1 should be improved: (1) the location of the fossil-bearing locality is too general. I suggest improving the map by increasing the zoom level and providing greater detail for the area where the record was found; (2) in the stratigraphic column on the left, italics should be removed from Sciuridae, as it is a suprageneric taxonomic category.

5. Figures 2 and 4: the main diagnostic characters (e.g., principal cusps, loph/ids, flex/ids, etc.) should be indicated in order to make the description easier to follow for non-specialist readers.

6. Figures 5 and 6: I suggest that the graphic quality and color of these figures be improved in order to better meet the standards of this journal.

Kind regards,

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what does this mean?). If published, this will include your full peer review and any attached files.). If published, this will include your full peer review and any attached files.). If published, this will include your full peer review and any attached files.). If published, this will include your full peer review and any attached files.

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Reviewer #1: Yes:Ferhat KayaFerhat KayaFerhat KayaFerhat Kaya

Reviewer #2: No

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First record of Sigmodon minor (Rodentia) in the early Blancan of central Mexico: asymmetrical dispersal from the Great Plains and paleoecology inferences

PONE-D-25-46840R1

Dear Dr. Wang,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

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Kind regards,

Pablo Colunga-Salas

Academic Editor

PLOS One

Additional Editor Comments (optional):

Dear authors,

It is with great pleasure that we announce that, following peer review, your manuscript has been accepted. Congratulations on this contribution to the taxonomy and fossil knowledge of sigmodontines. We are confident that this work will be warmly received by the scientific community.

Reviewers' comments: