Laser-stimulated fluorescence reveals unseen details in fossils from the Upper Jurassic Solnhofen Limestones

Laser-stimulated fluorescence (LSF) has seen increased use in palaeontological investigations in recent years. The method uses the high flux of laser light of visible wavelengths to reveal details sometimes missed by traditional long-wave ultraviolet (UV) methods using a lamp. In this study, we compare the results of LSF with UV-A-generated fluorescence on a range of fossils from the Upper Jurassic Solnhofen Limestone Konservat-Lagerstätte of Bavaria, Germany. The methodology follows previous protocols of LSF with modifications made to enhance laser beam intensity, namely keeping the laser at a constant distance from the specimen, using a camera track. Our experiments show that along with making surface details more vivid than UV-A or revealing them for the first time, LSF has the additional value of revealing shallow subsurface specimen detail. Fossil decapods from the Solnhofen Limestone reveal full body outlines, even under the matrix, along with details of segmentation within the appendages such as limbs and antennae. The results indicate that LSF can be used on invertebrate fossils along with vertebrates and may often surpass the information provided by traditional UV methods.

-Methods: Once again, UV appears to be less familiar to the authors. The distance, power/ output, duration of exposure and wavelengths must be varied to provide the promised comparison. Some specimens show overexposure, some do not. Virtually nobody successfully working with UV is happy after one certain procedure from a single publication. The entire paragraph (starting line 137) is outstandingly poor, as is the work behind. Only self-optimized procedures on the same specimens can be used for such a comparison, regarding any method included -Why are the results sorted by taxa? If possible, try to find methodical criteria to structure a methodical study, such as preservation, size of observed section, observed effects, setup, or usability -Why are some studied fossils not in the "results" section, but in a supplement? Why do some of them miss UV counterparts (including Fig. 8)? Right, it's said in the limitations section at the end, but why then using them anyway? Please provide a single, well-described result block, even if there's no UV for all -Camera setup / Fig. 1: Did the authors use an oblique perspective on the specimen, and if, how was it corrected? Is it possible to integrate a measuring grid, or how? Shouldn't workers be encouraged to use orthogonal views -maybe this is obvious and also meant in this way, but I'd recommend to design Fig. 1 according to such settings, to avoid unwanted implications (maybe lift specimen and objective, as the LASER works in an oblique angle anyway) - Were there any actions to compensate for the grid-like blurring in LSF imaging? Resolution is considerable low under LSF photographing, but as a central part of the results, is not sufficiently addressed in the paper - The siphuncle of the ammonite (Fig. 2) is visible also under normal light, which is usually found in Solnhofen fossils, so the caption is misleading for readers who are not familiar with such fossils in that the UV and LSF images are not the methods finally revealing this feature, or even details within -UV isn't UV. The application of UV A, B or C, or combinations, must be tested to compare detailed contrasts, instead of comparing LSF with some generalized "UV" technique. From own experiences, there are "Solnhofen-like" fossils that work only under UV A, while others revealed nothing except under UV C. The conclusions made here do not work at all, as they test only two different procedures, not method vs. method in general -Readers unfamiliar with the topic will find it easier to read a standardized vocabulary. Please use "UV" or "ultraviolet fluorescence", same with "LSF" vs. "LASER-stimulated fl.", same with the use of A, B, C… (found in some caption's sub-sections) -In Fig. 3, the use of LSF is convincing as a better tool than UV. Again, no differentiation of UV was performed. Furthermore, the role of intensity (total energy input) was neither controlled nor discussed. Many of the depicted fossils look overexposed (both UV or LSF), which can certainly support the detection of hidden details, but cause heavy blurring on the total image -For Fig. 4, and others, the detection of missing parts should be discussed in greater detail. Why are some sections missing, or look so? Is that due to locally changed preservation, or incomplete preparation? In the latter case, LASER stimulation might work through thin sheets of limestone -as said in the introduction: subsurface! The authors must underline that the big advantage they found (or applied) is just subsurface detection, not a comparison of various surface methods. In contrast, one edge of the telson is missing (Fig. 4), appearing black in both UV and LSF (due to sole imprint?) -Identification of the potential caudofemoralis muscle in Alligatorellus required more detail, as well as established UV control. The same bluish blurring occurs around the digits or inside the orbit. Would you conclude that this croc had webbed fingers? Or is there indication of matrix rock signals? From my experience, preparation liquids can cause intensive glow under UV -how about LSF then? -I cannot confirm that (by the comparison in Fig. 9) LSF surpassed UV (line 266) in any way that would concern anatomical documentation - The discussion is a mixture of introduction stuff, things that are already said, but again not explained (line 300), and awaited outlook. No discussion of true effects is given, which is no surprise due to the lack of any systematic variation of settings. In a methodical paper, I'd expect a  Viohl 1998: no short hyphen between limestone and genesis -I strongly recommend deleting the Archaeopteryx passage (starting line 63) and all related references, as there's no further link to this special field. To underline the meaning of "Solnhofen" plattenkalk fossils, address diversity and disparity, preservation, marine-terrestrial relation, Late Jurassic evolutionary transitions -but not the supposed one iconic textbook missing-link Archaeopteryx which is not even studied in the current submission. -A similar aspect is confusing regarding further citations: please just cite, instead of underlining avian/flight origins (line 93) as a special interest. -Again, the description of vertebrates (starting line 235) should lack a list of just nice fossil groups that were not studied, notably since this is the "results" section -"Solnhofen" in the used way is a generic term for many and partially not related lagerstaetten (line 110; which is why they are frequently referred to as Solnhofen archipelago, or Solnhofen-like plattenkalk). In the younger literature, this issue is increasingly recognized. Using "Solnhofen Limestones" or any other generalization is an unneeded step back. Same for Jehol: it must be plural (lagerstätten) in line 51 -In the caption of Fig. 9, "D" appears to be missing (typos in capital letters) The submitted manuscript is partially convincing as a method worth been applied for documentation. Unfortunately, severe issues concerning sharpness and systematic comparison are not addressed, nor documented in detail. Not least the use of UV deserves improvement, at least for a methodical paper The paper can be published as some sort of pioneer experiment, but must also clearly point out weaknesses (resolution) and so far undescribed comparisons (discretion of UV) If detection of so far unseen parts (for example, Fig. 6F) bases on incomplete preparation, LSF should be discussed as a chance to protect tricky specimens, or support their final preparation. If the detection of hidden parts is due to chemical remains, instead of subsurface stimulation, please explain in comparison In total, LSF is far from what I'd call a must-have method for the study of Solnhofen limestones. This can be gained by increased systematic experiments. Until then, the study should be discernable as a first initiative. Nonetheless, major revisions are needed to make this a sound study.
Decision letter (RSOS-210983.R0) We hope you are keeping well at this difficult and unusual time. We continue to value your support of the journal in these challenging circumstances. If Royal Society Open Science can assist you at all, please don't hesitate to let us know at the email address below.

Dear Mr Barlow
The Editors assigned to your paper RSOS-210983 "Laser-Stimulated Fluorescence reveals unseen details in fossils from the Upper Jurassic Solnhofen Lithographic Limestones of Bavaria, Germany" have made a decision based on their reading of the paper and any comments received from reviewers.
Regrettably, in view of the reports received, the manuscript has been rejected in its current form. However, a new manuscript may be submitted which takes into consideration these comments.
You will see that both reviewers see positive aspects to the paper and believe that the material could be valuable and interesting to readers, however both feel that the standard of presentation is significantly below that required for publication. Making appropriate revision will be quite time-consuming --not just a case of making limited changes in organisation or limited rewording. That is why the rejection allowing resubmission decision has been made. But Editors and reviewers alike hope that in due course you will be able to resubmit a version of the paper after having considered carefully how to address the general and specific comments of the reviewers.
We invite you to respond to the comments supplied below and prepare a resubmission of your manuscript. Below the referees' and Editors' comments (where applicable) we provide additional requirements. We provide guidance below to help you prepare your revision.
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Please resubmit your revised manuscript and required files (see below) no later than 02-Mar-2022. Note: the ScholarOne system will 'lock' if resubmission is attempted on or after this deadline. If you do not think you will be able to meet this deadline, please contact the editorial office immediately.
Please note article processing charges apply to papers accepted for publication in Royal Society Open Science (https://royalsocietypublishing.org/rsos/charges). Charges will also apply to papers transferred to the journal from other Royal Society Publishing journals, as well as papers submitted as part of our collaboration with the Royal Society of Chemistry (https://royalsocietypublishing.org/rsos/chemistry). Fee waivers are available but must be requested when you submit your manuscript (https://royalsocietypublishing.org/rsos/waivers). This paper represents a simple, concrete and worthwhile study to highlight the important interest of a -not much known -imaging technic adapted to the analysis of flat fossils (a type of preservation that refers to among the most nicely preserved Meso/Cenozoic animals), as in Plattenkalk. At the same time, it provides a new setup context for the applicability/usage of this method "in routine", or at least more commonly, by paleontologists during collection visit or at any lab, without requiring excessive equipment. The illustration set is nicely built and the whole UV/ new lab-based LSF comparison idea is very worth it. The big weakness of this whole manuscript is its little failure at sticking well to article writing standards, probably explained by the fresh experience of main authors in academia/paleo drafting. This should not be a limit to publication but required though an extensive rework of the manuscript -partitioning text, per standard article sections -targeting much better the -to be discussed -real aspects (say less but more specific) -and very important, re-writing of the results, which, once things have been cleared up, consist in total of only very few sentences per results sub-headings.
In order to do so, I encourage the authors at re-ordering their speech in a much more detailed comparative description, dealing with UV, and then LSF, and this in each of the 3 results subheading. I encourage describing much more the particularity of LSF as a rule, per group, and generally (as it is said once well only, in the conclusion), to give much more strength and specificities to the content of the manuscript, that right now is too "volatile". And also to introduce background on the imaging of specific fossils groups somewhere in material. For this, I placed in my review a set of highlights, changes and advices to guide the re-writing, hoping it will be of good help. Ultimately, a second/last polishing review will have to be brought to the reworked ms, after structural changes.
I finally hope that all authors, of all academic levels, could give an input to this end, to encourage and teach a progression toward the expected standard paper writing.
All best and success with paper modifications, Reviewer: 2 Comments to the Author(s) Review on RSOS-210983 -Laser-Stimulated Fluorescence reveals unseen details in fossils from the Upper Jurassic Solnhofen Lithographic Limestones of Bavaria, Germany L. Barlow et al. provide fossil photography using LSF and UV in comparison with "normal light" documentation. This is the first study applying LSF to a variety of macro-fossils from the Bavarian Upper Jurassic plattenkalk lagerstätten ("Solnhofen limestones"). Subsequent to an overview regarding non-destructive imaging methods applicable for such fossils, the authors describe photographic differences on a random series of specimens. In many details LSF shows impressive details, for which a general explanation is performed in a less focused manner. Abstract: -The supposed double use for both vertebrate and invertebrate studies deserves no discretion, as long as you do not refer to physical aspects (taphonomy, source of phosphate; see your citation of Wilby et al., 1996, line 67f) -LSF is said to "surpass… UV methods in some aspects" -if I'm right in that this advantage is mainly due to subsurface detection, please point out more clearly General topic and Figures -UV is stated to provide "low sensitivity and overemphasising effect on dust" (line 103f). This is a bit poor for a general characterization of UV photography. First, what is meant by sensitivity?
The camera's sensitivity? Or input/radiation, which can be adjusted. Dust, admittedly gleaming under UV, can be removed -Methods: Once again, UV appears to be less familiar to the authors. The distance, power/ output, duration of exposure and wavelengths must be varied to provide the promised comparison. Some specimens show overexposure, some do not. Virtually nobody successfully working with UV is happy after one certain procedure from a single publication. The entire paragraph (starting line 137) is outstandingly poor, as is the work behind. Only self-optimized procedures on the same specimens can be used for such a comparison, regarding any method included -Why are the results sorted by taxa? If possible, try to find methodical criteria to structure a methodical study, such as preservation, size of observed section, observed effects, setup, or usability -Why are some studied fossils not in the "results" section, but in a supplement? Why do some of them miss UV counterparts (including Fig. 8)? Right, it's said in the limitations section at the end, but why then using them anyway? Please provide a single, well-described result block, even if there's no UV for all -Camera setup / Fig. 1: Did the authors use an oblique perspective on the specimen, and if, how was it corrected? Is it possible to integrate a measuring grid, or how? Shouldn't workers be encouraged to use orthogonal views -maybe this is obvious and also meant in this way, but I'd recommend to design Fig. 1 according to such settings, to avoid unwanted implications (maybe lift specimen and objective, as the LASER works in an oblique angle anyway) -Were there any actions to compensate for the grid-like blurring in LSF imaging? Resolution is considerable low under LSF photographing, but as a central part of the results, is not sufficiently addressed in the paper -The siphuncle of the ammonite (Fig. 2) is visible also under normal light, which is usually found in Solnhofen fossils, so the caption is misleading for readers who are not familiar with such fossils in that the UV and LSF images are not the methods finally revealing this feature, or even details within -UV isn't UV. The application of UV A, B or C, or combinations, must be tested to compare detailed contrasts, instead of comparing LSF with some generalized "UV" technique. From own experiences, there are "Solnhofen-like" fossils that work only under UV A, while others revealed nothing except under UV C. The conclusions made here do not work at all, as they test only two different procedures, not method vs. method in general -Readers unfamiliar with the topic will find it easier to read a standardized vocabulary. Please use "UV" or "ultraviolet fluorescence", same with "LSF" vs. "LASER-stimulated fl.", same with the use of A, B, C… (found in some caption's sub-sections) -In Fig. 3, the use of LSF is convincing as a better tool than UV. Again, no differentiation of UV was performed. Furthermore, the role of intensity (total energy input) was neither controlled nor discussed. Many of the depicted fossils look overexposed (both UV or LSF), which can certainly support the detection of hidden details, but cause heavy blurring on the total image -For Fig. 4, and others, the detection of missing parts should be discussed in greater detail. Why are some sections missing, or look so? Is that due to locally changed preservation, or incomplete preparation? In the latter case, LASER stimulation might work through thin sheets of limestoneas said in the introduction: subsurface! The authors must underline that the big advantage they found (or applied) is just subsurface detection, not a comparison of various surface methods. In contrast, one edge of the telson is missing (Fig. 4) -I cannot confirm that (by the comparison in Fig. 9) LSF surpassed UV (line 266) in any way that would concern anatomical documentation -The discussion is a mixture of introduction stuff, things that are already said, but again not explained (line 300), and awaited outlook. No discussion of true effects is given, which is no surprise due to the lack of any systematic variation of settings. In a methodical paper, I'd expect a  1998: no short hyphen between limestone and genesis -I strongly recommend deleting the Archaeopteryx passage (starting line 63) and all related references, as there's no further link to this special field. To underline the meaning of "Solnhofen" plattenkalk fossils, address diversity and disparity, preservation, marine-terrestrial relation, Late Jurassic evolutionary transitions -but not the supposed one iconic textbook missing-link Archaeopteryx which is not even studied in the current submission. -A similar aspect is confusing regarding further citations: please just cite, instead of underlining avian/flight origins (line 93) as a special interest. -Again, the description of vertebrates (starting line 235) should lack a list of just nice fossil groups that were not studied, notably since this is the "results" section -"Solnhofen" in the used way is a generic term for many and partially not related lagerstaetten (line 110; which is why they are frequently referred to as Solnhofen archipelago, or Solnhofen-like plattenkalk). In the younger literature, this issue is increasingly recognized. Using "Solnhofen Limestones" or any other generalization is an unneeded step back. Same for Jehol: it must be plural (lagerstätten) in line 51 -In the caption of Fig. 9, "D" appears to be missing (typos in capital letters) The submitted manuscript is partially convincing as a method worth been applied for documentation. Unfortunately, severe issues concerning sharpness and systematic comparison are not addressed, nor documented in detail. Not least the use of UV deserves improvement, at least for a methodical paper The paper can be published as some sort of pioneer experiment, but must also clearly point out weaknesses (resolution) and so far undescribed comparisons (discretion of UV) If detection of so far unseen parts (for example, Fig. 6F) bases on incomplete preparation, LSF should be discussed as a chance to protect tricky specimens, or support their final preparation. If the detection of hidden parts is due to chemical remains, instead of subsurface stimulation, please explain in comparison In total, LSF is far from what I'd call a must-have method for the study of Solnhofen limestones. This can be gained by increased systematic experiments. Until then, the study should be discernable as a first initiative. Nonetheless, major revisions are needed to make this a sound study.

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Decision letter (RSOS-211601.R0)
We hope you are keeping well at this difficult and unusual time. We continue to value your support of the journal in these challenging circumstances. If Royal Society Open Science can assist you at all, please don't hesitate to let us know at the email address below.
Dear Mr Barlow, I am pleased to inform you that your manuscript entitled "Laser-Stimulated Fluorescence reveals unseen details in fossils from the Upper Jurassic Solnhofen Limestones" is now accepted for publication in Royal Society Open Science.
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Response to Reviewers
We wish to thank the editor and the two anonymous reviews for their constructive and helpful comments. Please see our point-by-point response below. We hope that you enjoy our revised manuscript.
Editor comments: Regrettably, in view of the reports received, the manuscript has been rejected in its current form. However, a new manuscript may be submitted which takes into consideration these comments.
You will see that both reviewers see positive aspects to the paper and believe that the material could be valuable and interesting to readers, however both feel that the standard of presentation is significantly below that required for publication. Making appropriate revision will be quite time-consuming -not just a case of making limited changes in organisation or limited re-wording. That is why the rejection allowing resubmission decision has been made. But Editors and reviewers alike hope that in due course you will be able to resubmit a version of the paper after having considered carefully how to address the general and specific comments of the reviewers.
Many thanks for your comments. We believe we have addressed the comments from Reviewer 1 and 2 in our revised manuscript and it has strengthened our manuscript.
Reviewer 1 comments: This paper represents a simple, concrete, and worthwhile study to highlight the important interest of a -not much known -imaging technic adapted to the analysis of flat fossils (a type of preservation that refers to among the most nicely preserved Meso/Cenozoic animals), as in Plattenkalk. At the same time, it provides a new setup context for the applicability/usage of this method "in routine", or at least more commonly, by paleontologists during collection visit or at any lab, without requiring excessive equipment. The illustration set is nicely built and the whole UV/ new lab-based LSF comparison idea is very worth it.
We thank the reviewer for believing that our manuscript will form a nice submission to this journal as it was our intention to bring this technique to a wider audience along with displaying new comparative results.
The big weakness of this whole manuscript is its little failure at sticking well to article writing standards, probably explained by the fresh experience of main authors in academia/paleo drafting. This should not be a limit to publication but required though an extensive rework of the manuscript -partitioning text, per standard article sections -targeting much better the -to be discussed -real aspects (say less but more specific) -and very important, re-writing of the results, which, once things have been cleared up, consist in total of only very few sentences per results sub-headings.
Many thanks for the constructive bullet points and we have done our best to address the above concerns. This revised manuscript has been reduced in size to take out unnecessary information.
In order to do so, I encourage the authors at re-ordering their speech in a much more detailed comparative description, dealing with UV, and then LSF, and this in each of the 3 results subheading. I encourage describing much more the particularity of LSF as a rule, per group, and generally (as it is said once well only, in the conclusion), to give much more strength and specificities to the content of the manuscript, that right now is too "volatile". And also to introduce background on the imaging of specific fossils groups somewhere in material. For this, I placed in my review a set of highlights, changes and advices to guide the re-writing, hoping it will be of good help. Ultimately, a second/last polishing review will have to be brought to the reworked ms, after structural changes.
Thanks so much for providing a detailed set of highlights on the manuscript which became a starting point for the changes made and was extremely helpful to have.
I finally hope that all authors, of all academic levels, could give an input to this end, to encourage and teach a progression toward the expected standard paper writing.
All best and success with paper modifications, Reviewer 2 comments: L. Barlow et al. provide fossil photography using LSF and UV in comparison with "normal light" documentation. This is the first study applying LSF to a variety of macro-fossils from the Bavarian Upper Jurassic plattenkalk lagerstätten ("Solnhofen limestones"). Subsequent to an overview regarding non-destructive imaging methods applicable for such fossils, the authors describe photographic differences on a random series of specimens. In many details LSF shows impressive details, for which a general explanation is performed in a less focused manner.
Abstract: -The supposed double use for both vertebrate and invertebrate studies deserves no discretion, as long as you do not refer to physical aspects (taphonomy, source of phosphate; see your citation of Wilby et al., 1996, line 67f) -LSF is said to "surpass… UV methods in some aspects" -if I'm right in that this advantage is mainly due to subsurface detection, please point out more clearly These points have been noted and changed accordingly making subsurface detection far more pointed out in our revised manuscript. Well pointed out by the reviewer and cyan-red photography has been mentioned in comparative methods. The study was restricted to UV-A vs LSF as UV-A is well established in palaeontology and the equipment was most accessible. We believe the comparison between LSF on a new site and other groups of fossils with UV-A is worthwhile.
-UV is stated to provide "low sensitivity and overemphasising effect on dust" (line 103f). This is a bit poor for a general characterization of UV photography. First, what is meant by sensitivity? The camera's sensitivity? Or input/radiation, which can be adjusted. Dust, admittedly gleaming under UV, can be removed We believe this has been made clearer now.
-Methods: Once again, UV appears to be less familiar to the authors. The distance, power/ output, duration of exposure and wavelengths must be varied to provide the promised comparison. Some specimens show overexposure, some do not. Virtually nobody successfully working with UV is happy after one certain procedure from a single publication. The entire paragraph (starting line 137) is outstandingly poor, as is the work behind. Only self-optimized procedures on the same specimens can be used for such a comparison, regarding any method included Thank you for the detailed criticism. The blanket studying of fossils under UV-A followed a well-established method so while they could have been further optimised, the figures still show adequate information for a comparison to be made. The paragraph has been reworked to a level we believe is better.
-Why are the results sorted by taxa? If possible, try to find methodical criteria to structure a methodical study, such as preservation, size of observed section, observed effects, setup, or usability This has been changed and the results now consist of two headings for each technique.
-Why are some studied fossils not in the "results" section, but in a supplement? Why do some of them miss UV counterparts (including Fig. 8)? Right, it's said in the limitations section at the end, but why then using them anyway? Please provide a single, well-described result block, even if there's no UV for all Limitations has now been moved to Materials and Methods section. Results are now in a single block.
-Camera setup / Fig. 1: Did the authors use an oblique perspective on the specimen, and if, how was it corrected? Is it possible to integrate a measuring grid, or how? Shouldn't workers be encouraged to use orthogonal viewsmaybe this is obvious and also meant in this way, but I'd recommend to design Fig. 1 according to such settings, to avoid unwanted implications (maybe lift specimen and objective, as the LASER works in an oblique angle anyway) The figure has been fixed to avoid any confusion, thank you for the suggestions.
-Were there any actions to compensate for the grid-like blurring in LSF imaging? Resolution is considerable low under LSF photographing, but as a central part of the results, is not sufficiently addressed in the paper No there we no actions, we provide a simple method that others can replicate easily.
-The siphuncle of the ammonite (Fig. 2) is visible also under normal light, which is usually found in Solnhofen fossils, so the caption is misleading for readers who are not familiar with such fossils in that the UV and LSF images are not the methods finally revealing this feature, or even details within We have now addressed this to prevent misleading future readers. See line 204.
-UV isn't UV. The application of UV A, B or C, or combinations, must be tested to compare detailed contrasts, instead of comparing LSF with some generalized "UV" technique. From own experiences, there are "Solnhofen-like" fossils that work only under UV A, while others revealed nothing except under UV C. The conclusions made here do not work at all, as they test only two different procedures, not method vs. method in general We disagree that our UV-A method is insufficient for displaying results as it is well documented on in various Solnhofen papers using UV-A (365 nm) which is what was used in this paper. UV-A has been more clearly stated in the paper.
-Readers unfamiliar with the topic will find it easier to read a standardized vocabulary. Please use "UV" or "ultraviolet fluorescence", same with "LSF" vs. "LASER-stimulated fl.", same with the use of A, B, C… (found in some caption's sub-sections) Thank you for this, we have made these changes.
-In Fig. 3, the use of LSF is convincing as a better tool than UV. Again, no differentiation of UV was performed. Furthermore, the role of intensity (total energy input) was neither controlled nor discussed. Many of the depicted fossils look overexposed (both UV or LSF), which can certainly support the detection of hidden details, but cause heavy blurring on the total image LSF and UV-A have always been used as tools for detecting unseen details. We agree that the images could be sharper, but the important details are still evident, overexposed or otherwise.
-For Fig. 4, and others, the detection of missing parts should be discussed in greater detail. Why are some sections missing, or look so? Is that due to locally changed preservation, or incomplete preparation? In the latter case, LASER stimulation might work through thin sheets of limestoneas said in the introduction: subsurface! The authors must underline that the big advantage they found (or applied) is just subsurface detection, not a comparison of various surface methods. In contrast, one edge of the telson is missing (Fig. 4), appearing black in both UV and LSF (due to sole imprint?) Thank you for pointing these out and we agree, making this clearer in our revised manuscript.
-Identification of the potential caudofemoralis muscle in Alligatorellus required more detail, as well as established UV control. The same bluish blurring occurs around the digits or inside the orbit. Would you conclude that this croc had webbed fingers? Or is there indication of matrix rock signals? From my experience, preparation liquids can cause intensive glow under UVhow about LSF then?
More detail has now been added. Glue has also been mentioned to glow under fluorescence. Starting line 538.
-I cannot confirm that (by the comparison in Fig. 9) LSF surpassed UV (line 266) in any way that would concern anatomical documentation We disagree with this point as the skull, vertebral column and tail are all different under LSF compared with UV-A.
-The discussion is a mixture of introduction stuff, things that are already said, but again not explained (line 300), and awaited outlook. No discussion of true effects is given, which is no surprise due to the lack of any systematic variation of settings. In a methodical paper, I'd expect a table or close meshed structure of advantages/disadvantages, possible ranges, combined values… We do not believe a table is necessary, but we have reworked the discussion so that it reads easier.
-If possible, please give an outlook on possible microscopic use Done, see line 256.
-Limitations section: This should be part of the methods block (limited equipment, incomplete UV comparison) We agree and it has now been moved.
Minor comments -If T. Kaye is a contributing author, is a pers.-comm. citation the right way? (line 45) This has now been removed.
-Please correct brackets vs. comma in line 54 Corrected.
-Reference list: Viohl 1998: no short hyphen between limestone and genesis This has now been fixed in the revised manuscript.
-I strongly recommend deleting the Archaeopteryx passage (starting line 63) and all related references, as there's no further link to this special field. To underline the meaning of "Solnhofen" plattenkalk fossils, address diversity and disparity, preservation, marineterrestrial relation, Late Jurassic evolutionary transitionsbut not the supposed one iconic textbook missing-link Archaeopteryx which is not even studied in the current submission. -A similar aspect is confusing regarding further citations: please just cite, instead of underlining avian/flight origins (line 93) as a special interest. -Again, the description of vertebrates (starting line 235) should lack a list of just nice fossil groups that were not studied, notably since this is the "results" section This has been taken onboard and the sections have been removed in the revised manuscript.
-"Solnhofen" in the used way is a generic term for many and partially not related lagerstaetten (line 110; which is why they are frequently referred to as Solnhofen archipelago, or Solnhofen-like plattenkalk). In the younger literature, this issue is increasingly recognized. Using "Solnhofen Limestones" or any other generalization is an unneeded step back. Same for Jehol: it must be plural (lagerstätten) in line 51 The plural of lagerstätten has now been edited. We do not think the use of Solnhofen limestones is an issue to address.
-In the caption of Fig. 9, "D" appears to be missing (typos in capital letters) Corrected.
The submitted manuscript is partially convincing as a method worth been applied for documentation. Unfortunately, severe issues concerning sharpness and systematic comparison are not addressed, nor documented in detail. Not least the use of UV deserves improvement, at least for a methodical paper The paper can be published as some sort of pioneer experiment, but must also clearly point out weaknesses (resolution) and so far undescribed comparisons (discretion of UV) Thanks for seeing some worth in the paper in its current state and we have done our utmost to make the changes required for resubmission.
If detection of so far unseen parts (for example, Fig. 6F) bases on incomplete preparation, LSF should be discussed as a chance to protect tricky specimens, or support their final preparation. If the detection of hidden parts is due to chemical remains, instead of subsurface stimulation, please explain in comparison This has been made clearer in the revised manuscript. Line 278.
In total, LSF is far from what I'd call a must-have method for the study of Solnhofen limestones. This can be gained by increased systematic experiments. Until then, the study should be discernable as a first initiative. Nonetheless, major revisions are needed to make this a sound study.
We thank the reviewer for noticing this as a first initiative. We feel that the revisions should be more than sufficient.