Content of review 1, reviewed on July 07, 2014

Basic reporting

In general, this is a carefully considered and well-argued contribution. However, the MS could be shortened somewhat by removal of some unnecessary repetition. Also, the wording can be tightened, and altered in certain places to avoid language that does not comply with generally accepted scientific standards. I also found some of the language very awkward and in places confusing and have have made numerous suggestions for changes on the annotated MS.

Anatomical descriptions are refreshingly clear and concise. But there are one or two examples of ambiguous wording. This should be altered where indicated and figures provided (see below).

No description of characters defining Atoposauridae is provided and differential diagnoses are lacking. I do not feel the MS is complete without them.

References are in good order except where indicated but the authors need to check for compliance with journal style requirements, mostly in the case of references to articles and chapters appearing in books (which I have not done in the case of any aspect of the MS). However, Fiorillo 1999 is cited in the text but is not included in the list of references and Buscalioni et al. 2011 appears in the list but is not cited in the text.

So far as figures are concerned, Fig. 1 shows dotted lines in black for Theriosuchus sp. and Atoposauridae indet. No explanation of the geographical occurrence(s) is provided. Furthermore, I suspect that indeterminate isolated teeth representing atoposaurids are known from deposits throughout their spatiotemporal range. E.g. indeterminate (or possibly undetermined) teeth representing a small atoposaurid are abundant among microvertebrate remains recovered from the Barremian Wessex Formation (Sweetman. 2011. Text-fig. 16.4E,F p. 201, in Batten (ed.) Palaeontological Association Field Guide to Fossils 14. English Wealden Fossils. Pal. Ass. London).

As mentioned in an annotation, I think it would be better to place the anatomical annotations shown in Fig. 2 below the institutional abbreviations. With regard to the former, the authors should give thought to their format and the use of capital letters, e.g. AF is used for Antorbital fenestra whereas Cav is used for caudal vertebra. This looks untidy to my eye. Perhaps use juxtaposed capitals only for osteoderms?

Figures of described specimens, so far as they go, are satisfactory but the authors need to provide detailed drawings of many of the elements they describe (unless these were provided by Wellnhofer (1971), in which case reference to his figures should be provided in the text where appropriate). Additional figures must include skull diagrams to aid comparisons between Alligatorellus beaumonti and A. bavaricus.

There was no reference to Fig. 6 in the text. I have made one suggestion but, if it is retained, reference to it should be made elsewhere. I find comparison between A and B confusing. Localities 5 and 6 are shown in the same place on each map but B shows the Iberian Peninsula as it was before the current configuration was achieved. Also, what does the diagonal line towards the bottom in B represent? Paleaogeography did not change much between the Late Jurassic and Early Cretaceous and the map provided is simplistic and schematic so I think it would be useful to include early Cretaceous occurrences (indicated by a different coloured dot) as these are discussed in the text.

In the case of all Figs. capital letters are used do designate elements in each whereas lowercase letters are used in the captions. Also, in Fig. 6 bold text is not required. The Captions should be changed.

Experimental design

NA

Validity of the findings

I agree with the authors’ re-evaluation of the taxa discussed. I also agree with their comments concerning allopatric speciation, not least because a recent study has confirmed that very short geographical separations can result in speciation (Sweetman et al. In press. A new bernissartiid crocodyliform from the Lower Cretaceous Wessex Formation (Wealden Group, Barremian) of the Isle of Wight, southern England. Acta Pal. Pol.). However, I strongly disagree with those concerning insular dwarfism. There is no evidence for this so far as crocodyliforms in this part of Laurasia are concerned.

Looking at the Early Cretaceous (Berriasian – Early Aptian, a time span of at least 20 million years during which the area under consideration still comprised an island archipelago) diminutive crocodyliforms such as atoposaurids coexisted with large forms, e.g. goniopholids. Early Cretaceous atoposaurids appear to have been about and remain the same size as they were during the Late Jurassic and there is no sign of a reduction in size of large taxa. It seems much more likely to me that size difference relates to adaptations between taxa to exploit different trophic resources in the environments in which they coexisted. Furthermore, the authors fail to but should make mention of bernissartiid crocodyliforms. These are of a similar size to coexisting atoposaurids but with a unique dentition indicating further environmental partitioning among small crocodyliforms. A couple of words concerning the small size of atoposaurids is appropriate but the long discussion about dwarfism should be removed.

Comments for the author

In addition to the above please refer to the annotated MS and advise the editor if you would like this as a Word document. Please also note that the title and abstract page was tacked onto the top of the main part of the MS as it was not part of the source file. Two deleted words near the bottom of the abstract (three and the) are not shown as such in the markup.

Please note that I am somewhat dyslexic. I may have made typographical errors in some of my comments and may not have seen others in the original MS.

Source

    © 2014 the Reviewer (CC-BY 4.0 - source).

References

    P., T. J., D., M. P. 2014. Revision of the Late Jurassic crocodyliform Alligatorellus, and evidence for allopatric speciation driving high diversity in western European atoposaurids. PeerJ.