The Origin of the Mangrove and Saltmarsh Snail Ellobium (Eupulmonata, Ellobiidae)^†

Round 1

Reviewer 1 Report

Mollusca Base is not a very reliable source. Cite rather original publications. All the taxa, even genera, are based solely on the shell. which for me is rather unusual, especially since some of the representatives of the genus are still extant. There are no methods. In the description of the new genus there is no differential diagnosis, following the rules of ICZN. later in the discussion the differences are given, but they should be listed in differential diagnosis, not just mentioned somewhere. Line 140-141 - too speculative. In the description of a new species the differential diagnosis is also lacking.

Line 289-290: "...is reminiscent of the Paratethyanspecies in its general outline... Whar does it mean? which outline? of phylogeny? of the shell shape? of geography?

Line 137-138: "large and beautiful species'? What does it mean? How a species may be large?

Line294-295: "Concerning the prominent palatal swelling E. kerwaense nov. sp. is closer... How and why closer? In shape? Phylogenetically? Why?

Line 359-360: "is superficially reminiscent of E. subjudae in its elongate outline" please rephrase

Lines 429-433 - the analogy between the truly marine Tridacna and Strombus vs brackishwater/amphibious Ellobium is hardly justified

Author Response

Dear Colleague,

thank you for the kind review which was easy to follow.  In the folowing we anser your points step by step:

Language: Bernard Landau is a native speaker and went through the text again.  

Mollusca Base is not a very reliable source. Cite rather original publications.

This is true but it is a widely accepted platform and is run by experts in the field. It is the only available source where all fossil and extant Ellobium species are listed (though uncritically). No conclusion is based by us on this list and for seven of the extant species we give references and ecological data. Therefore, we do not see a problem with referring to MolluscaBase. Moreover, we discuss those species for which we disagree with molluscabase.

All the taxa, even genera, are based solely on the shell. which for me is rather unusual, especially since some of the representatives of the genus are still extant.

We are dealing with fossils and therefore we cannot refer to anatomical data. Nevertheless, we have added a reference on anatomical data of Ellobium in the diagnosis of the genus.

In the description of the new genus there is no differential diagnosis, following the rules of ICZN. later in the discussion the differences are given, but they should be listed in differential diagnosis, not just mentioned somewhere.

we have added this in the diagnosis

Line 140-141 - too speculative.

We kindly disagree. We wrote “might represent”, which is a hypothesis and we would like to have this hypothsis be documented for future discussions.

Line 289-290: "...is reminiscent of the Paratethyans pecies in its general outline... What does it mean? which outline? of phylogeny? of the shell shape? of geography?

we mean shell shape. This is clarified now

Line 137-138: "large and beautiful species'? What does it mean? How a species may be large?

This is a verbatim translation of the original French translation. We cannot modify this.

Line294-295: "Concerning the prominent palatal swelling E. kerwaense nov. sp. is closer... How and why closer? In shape? Phylogenetically? Why?

we mean morphologically (added)

Line 359-360: "is superficially reminiscent of E. subjudae in its elongate outline" please rephrase

we have deleted “superficially”

Lines 429-433 - the analogy between the truly marine Tridacna and Strombus vs brackishwater/amphibious Ellobium is hardly justified

This is a good point and we have added a line that both groups had different ecologies and habitats.

Reviewer 2 Report

The manuscript "The origin of the mangrove and saltmarsh snail Ellobium (Eupulmonata, Ellobiidae)":

I found the entire manuscript to be expertly and very clearly written. So clearly written that I had barely any questions and I would thus recommend to publish this without changes. In fact, I several times found arising questions (e.g. "are there *any* old ellobiid fossils from the Eastern Tethys/present IWP area? Or are these only from Europe?") to be answered by the authors only a few lines afterwards. The main hypothesis is clearly argued and the figures are of excellent quality and perfectly augment the text. Congratulations to the authors to their work!

It also seems entirely fair that the authors decided to not discuss their finding (paraphrased by myself as "European origin of Ellobium") in the larger context of ellobiid phylogeny, which may open more questions about biogeography and the fossil record than are within the sensible scope of this paper.

Minor thoughts on specific chapters (which I hope, may be in some way valuable feedback to the authors): 

 - Introduction as a whole: I appreciated the very clear yet detailed explanation and listing of extant and extinct species. The habitat of Ellobium species, line 63: "Comparable habitat requirements are proposed by us for fossil species" led me to wonder if there are, then, clear cases where the fossil record of Ellobium spp. also contains fossil species of the gastropod genera you discuss before, namely Cerithidea and Nerita? (Your lines 147-148 seem to say otherwise due to the mixing of many taxa at the fossil sites).

- The fossil record: I found this question to be satisfactorily answered in the Discussion section, but the authors might consider (or not) to already briefly add here that the majority of discussed fossil Ellobium species are from Europe but not from other places. At this point of the manuscript it might seem that the European origin COULD be a bias in the literature (simply because the two major works cited in l. 69-71 focus on Europe only). Line 73, "Since then, several new species have been described" also led me to ask if these are also all from Europe? It appears from the names of species and authors that they are (I did not check), but if not, please add the localities for listed species that are not from Europe (if there are any).

- Systematics, chapter Diagnosis of Eoellobium: perhaps it may be helfpul to readers who are not specialists in gastropod apertural dentition to briefly repeat what the columellar and parietal folds are or where they are located. This COULD be shown by small arrows e.g. in Fig. 1 (the shell in 1B showing three folds) or simply explained in a half-sentence in the text. Same for the term "fasciole".

Further notes that are, however, essentially editorial: 

line 95 "differ considerably from extant Ellobium species" - ... in morphology and fossil age?

l 130 clicking the second link presently does not lead to a valid page due to the hyphenation dividing "catalognumber"

l 190 "resulting in irregularly granulose" - there is a word missing here.

l 225: "inner shell walls partly resorbed" - I would assume this character is also not present in Eoellobium? Is this possible to tell from any of the known, broken, fossils?

l 274: "Fasciole broad, indistinct" - see above. Perhaps briefly explain the term fasciole in this context?

l 433: genus name presently not in italics

Congratulations to the authors to their work!

Author Response

We thank Reviewer 2 for the positive feedback and try to answer his comments and suggestions in the following:

 - Introduction as a whole: I appreciated the very clear yet detailed explanation and listing of extant and extinct species. The habitat of Ellobium species, line 63: "Comparable habitat requirements are proposed by us for fossil species" led me to wonder if there are, then, clear cases where the fossil record of Ellobium spp. also contains fossil species of the gastropod genera you discuss before, namely Cerithidea and Nerita? (Your lines 147-148 seem to say otherwise due to the mixing of many taxa at the fossil sites).

We added a line on the co-occurrence of Nerita and Potamididae with the fossil species.

The fossil record: I found this question to be satisfactorily answered in the Discussion section, but the authors might consider (or not) to already briefly add here that the majority of discussed fossil Ellobium species are from Europe but not from other places. At this point of the manuscript it might seem that the European origin COULD be a bias in the literature (simply because the two major works cited in l. 69-71 focus on Europe only). Line 73, "Since then, several new species have been described" also led me to ask if these are also all from Europe? It appears from the names of species and authors that they are (I did not check), but if not, please add the localities for listed species that are not from Europe (if there are any).

This is true and we have added a line on set: Overall, our knowledge on the history of Ellobium is clearly biased towards European occurrences.

Systematics, chapter Diagnosis of Eoellobium: perhaps it may be helfpul to readers who are not specialists in gastropod apertural dentition to briefly repeat what the columellar and parietal folds are or where they are located. This COULD be shown by small arrows e.g. in Fig. 1 (the shell in 1B showing three folds) or simply explained in a half-sentence in the text. Same for the term "fasciole".

We prefer not to insert arrows in the figure because this is quite unusual and would obscure parts of the pictures. However, we have added a short note in the methods that the terminology follows Cox 1960. This is a standard reference and widely accepted.

line 95 "differ considerably from extant Ellobium species" - ... in morphology and fossil age?

clarified (conchological features)

130 clicking the second link presently does not lead to a valid page due to the hyphenation dividing "catalognumber"

it does work if copied to the browser. I do not know how I could change it.

190 "resulting in irregularly granulose" - there is a word missing here.

“surface” added

225: "inner shell walls partly resorbed" - I would assume this character is also not present in Eoellobium? Is this possible to tell from any of the known, broken, fossils?

we don’t know because there is no broken shell

274: "Fasciole broad, indistinct" - see above. Perhaps briefly explain the term fasciole in this context?

we have referred to Cox 1960 in the methods where all terms are explained

433: genus name presently not in italics

done