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This manuscript has been improved significantly and all statements and findings are supported by evidence and documented. This careful study is ready for publication.
All issues from previous review have been adequately addressed.
This manuscript is publishable but requires careful reconsideration and rewriting. The discussion of body size will need to include the points made by reviewer 2. Also, it would benefit from discussing the relevance of work on modern balaenids, such as that of George et al, 2016 (PLoS One), and references cited therein (including different models for estimating size based on length). Balaenids grow throughout life and their neck vertebrae fuse very gradually which was documented by Moran et al (2015, J. Mammal Evol). A figure needs to be added along the lines of comment 2 of reviewer 2, I am less concerned about 1 and 3.
Reviewer 2 read the manuscript very carefully, please also take care of his minor comments. Reviewer 1 provided an annotated manuscript.
Good. Several comments are placed in the manuscript itself suggesting minor improvements.
Good. Phylogenetic procedures are sound. Identifications of possible ancestral relationships are sound, although the multi-point reasoning for why they consider their species an ancestor seems much too long.
Good. I'm surprised the phylogenetic analysis only produced a single tree. More explanation of how good alternative trees are would be helpful.
Overall the manuscript is verbose. Perhaps the authors could try to trim the language overall to make it shorter and more succinct.
This paper redescribes a historically important specimen of a right whale from the Pliocene of Belgium, reevaluates the incomplete holotype cervical vertebrae of Balaena belgica, and erects the new name Eubalaena ianitrix for the skull reported in the 1960s. The paper is quite important for students of marine mammal evolution, Pliocene marine mammal assemblages, and baleen whale evolution, and will be publishable with some revision. The paper is of excellent quality and minimal language polishing is required. I've made a few major suggestions and a long list of minor corrections. I trust the authors to make these, and will leave the decision up to the editor. The authors should implement all the minor comments and seriously consider the major comments, which would strongly improve the paper.
Kind regards, Robert W. Boessenecker
This study would benefit from some kind of ancestral character state reconstruction for body size, and would strengthen the case for interpreting ancestor-descendant relationships in the E. ianitrix-glacialis lineage. I suggest using body length rather than mass as per arguments made in Churchill et al. (2014: Journal of Anatomy 225:232-245); a simple ACR would be quite informative and could help exclude the hypothesis that small body size is derived rather than primitive in E. ianitrix. Furthermore, extra figures, and some more substantive discussion of body size as relating to sea surface temperature in the proto-North Sea would greatly improve the appeal and importance of the study.
A few extra figures would be highly informative, including:
1) A series of comparative line drawings comparing the crania of various Eubalaena spp., Eubalaena ianitrix, and other modern/fossil balaenids.
2) A figure showing body size in the Balaenidae. Perhaps this could be done with silhouettes scaled to size.
3) Fig. 13 is useful but the character states should be spelled out and completely labeled so that the reader does not need to refer to the appendix. Additional views, and comparative photos with other balaenids would really make this figure useful rather than numbers in a vacuum.
Lines 62-67: This list is incomplete. I reported specimens of Eubalaena from the Pliocene Purisima Formation of California (Boessenecker, 2013: Geodiversitas); Field et al. (2017: Palaeontology) very recently reported a specimen of Eubalaena from the Pliocene Tjornes Formation of Iceland, and Morgan (1994:250; Proceedings of the San Diego Soc. Nat. Hist.).
Line 73: should cite inclusion of B. belgica in the Marx and Fordyce (2015) analysis here.
74-75: “lacking…assignment” this wording is awkward and should be rephrased.
93: change to “bowhead whales (1) reveal the timing of the origin”
121: change “about” to “for”
179: This is not correct. Eubalaena shinshuensis has already been coded into several analyses, including Fordyce and Marx (2015) and Boessenecker and Fordyce (2015A, 2015B, 2016).
210: change “were” to “where”
368: change “big” to “large”
369: perhaps listing the maximum humeral lengths would be useful – e.g. Balaena mysticetus (XX mm), Eubalaena glacialis (XX mm)
424: does an unnamed species need to be included in the diagnosis?
428: “differently shaped” – please be specific
Diagnosis section: while this is a differential diagnosis in the truest possible sense, it should probably also list some autapomorphies and characterize the taxon rather than just include a list of comparisons.
444: the family Balaenidae is transversely compressed? Suggest changing to “transverse compression present in Balaenidae”
538: Abrasion has a very specific preservational definition, and that is attritional damage to bone caused by sediment interaction. I suspect that many of the damaged parts of the skull relate to damage during collection, which falls outside the definition of abrasion.
539: change to “a convex lateral border and a widely rounded”
545: “relieves” – unclear.
556: “parassial” – unclear. Parasaggital?
566-567: What are the proportions? A comparative figure showing line drawings or even photographs would be highly informative.
575-576: There is a paper by Tadasu Yamada et al. (2006) which discusses the problems with photographing large mysticetes and would be a relevant citation here: Yamada, T. K., Chou, L.-S., Chantrapornsyl, S., Adulyanukosol, K., Chakravarti, S. K., Oishi, M., et al. (2006). Middle sized balaenopterid whale specimens (Cetacea: Balaenopteridae) preserved at several institutions in Taiwan, Thailand, and India. Memoirs of the National Science Museum, Tokyo, 44, 1–10
582: change “superimposed onto” to “overlaps”
604: reniform might be a good substitute for kidney-shaped
606: “inclined…point” is awkward and should be rephrased.
606: Concavity sounds like the ventral condyloid fossa, but the writer appears to mean the intercondylar notch.
607-610: this should be included in a table and seems a bit out of place here.
612: anteroposterior seems wrong here, and should be dorsoventral.
627: Which direction is the zygomatic process short and stocky?
629: delete “it is”
635: From what I remember the tympanosquamosal recess is an odontocete feature.
639: “falciform…anteriorly”. This statement is uninformative and should be clarified with specifics. Is it transversely narrow and sharp? Is it parasagittally oriented? Is it “higher” posteriorly or anteriorly? Where does it begin/end?
640: change “included between” to “formed between” or “bordered by”
643: widely rounded…. In the transverse plane?
643: zygomatic process of frontal – is this not the postorbital process?
648: there is an extra space after B. montalionis.
654: delete “the posterior border of”
669: “are worn” – change to damaged or incomplete
709: olive shape – this is unclear. Oval shaped?
Body size estimate (713-732): A few statements about body size comparisons (e.g. with extant mysticetes and other extinct balaenids) would be useful here.
753: All of this should be included in the main text since this is PeerJ and has no page limits.
775: what is a “low tympanic cavity”?
856: “The calculus” – please clarify. Calculation?
913-918: It is important to note here that the McLeod et al. phylogeny was not computer-assisted and is a hand-drawn phylogeny.
973: A citation of Tsai and Fordyce (2015) on ancestor-descendant relationships or their paper and their paper on heterochrony in mysticetes should be included here.
1023-1024: Do these parasites have a fossil record? If not, then this is a moot point.
1050: The publication year for Churchill et al. is 2012.
1057: A citation is needed for the divergence dates between Neobalaenidae and Balaenidae.
1062: change to “scope”
1089: change “shortcuts” to “shortcomings”
1067-1074: Ancestor-descendant relationships have also been demonstrated for the fur seal Callorhinus (Boessenecker, 2011: J. Vert Paleo), great white sharks (Ehret et al. 2012: Palaeontology), and the dinosaur Triceratops (Scannella et al. 2014: PNAS).
1101-1105: Why? Eubalaena could have dispersed through equatorial waters or through the arctic portal numerous times during this period. See Boessenecker (2013: Geodiversitas), Peredo and Uhen (2016: PPP) and Churchill et al. (2014: Zoological Journal of the Linnean Society).
1117: The 2 million years species longevity is a complete guess appearing in multiple works which RE Fordyce is attached to. It’s not really based on densely sampled parts of the cetacean fossil record. I don’t think it’s unreasonable, but there’s not any paleontological evidence supporting it. It’s based on Pleistocene occurrences of modern taxa, but it’s unclear whether these are A) truly identifiable to modern species and B) unclear whether these species are preserved in the Pliocene. So, a longer or shorter longevity is possible given the data.
1127-1130: Another possibility, and I think the authors should attempt this, would be to investigate the temperature tolerance of extant Eubalaena spp., and compare it with the paleotemperature of the Lillo Fm. and see if this could explain the difference in body size in a quantifiable manner.
1151: What about during the Pliocene? The current record provides evidence that Eubalaena and Balaena were sympatric during the Pliocene in the North Atlantic (Field et al., 2017).
Fig. 12: Tokarahia is misspelled as Tokaraia
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