This is a nicely illustrated paper of an important specimen. A few areas of minor change are suggested, particularly in addressing issues of geological context, specimen association, and scaling / allometry. Additionally, because so much of the topic has systemetic relevance, a revised diagnosis should be presented for Barosaurus lentus. Finally, some of the descriptions could be augmented in places to create a more comprehensive treatment of the specimen.
p. 1: "Barosaurus is widely thought of as merely Diplodocus with a longer neck." - This statement really needs some context. Has anyone actually said this in print? I recognize that these sorts of memes are often passed from researcher to researcher, but does anyone actually believe this? (later in the paper are some statements that might indicate this, but they really should be up front). Is there a recent diagnosis of the taxon that would indicate such things? Is this a longer neck relative to torso length? Femur length? Is it real, or just a meme?
- Vertebra T is dismissed as too incomplete, but shouldn't it still get a brief description and photos? Or are we talking so incomplete as to be doubtful as a vertebra?
- Because you focus a great deal on anatomy of the neck in Barosaurus, and distinguishing it from Diplodocus, you really should provide a revised diagnosis for Barosaurus. This is partway given in the conclusions, but it is not anything of real utility. If one of the goals of the paper is to provide new information on the neck of Barosaurus, this information should be put to use! As an overall note, I would recommend including a full systematic paleontology section, with taxonomic authorities, referred material, stratigraphic horizons, autapomorphic and differential diagnoses, etc. Minimal work, maximal utility to the reader.
- Figure 2. Include a scale bar (here and elsewhere). Yes, parallax is an issue. As a compromise, indicate where the scale bar is relative to the specimen, as a way to acknowledge parallax. For figures like Figure 4, the lack of a scale bar is a serious deficit. When I see vertebrae of different shapes and from different taxa, I immediately think about scaling effects and the like. Without a scale bar and some way to tell intuitively which vertebrae are largest and which are smallest, the reader is left in the dark. In fact, scaling effects are pretty much ignored in this paper. How do the sizes of the vertebrae in Barosaurus stack up relative to those of Diplodocus, Apatosaurus, etc.? How big are the vertebrae of AMNH 6341 vs. YPM 429? They are said to be roughly the same size (p. 19), but if measurements are available (or can be estimated), this should be quantified.
- Figure 3. The orientation of anterior and posterior views are odd. I would put them into "standard" position, with dorsal to the top and ventral to the front. Also, add letters to the figure to indicate which view is which. The same goes for other figures in this paper.
- Give strong consideration to including interpretive line drawings that label portions of the figure, or at a minimum, some labeling on the photographic plates. Not every reader is going to know where the lateral laminae are, and things such as the neural spine are not immediately obvious on some views of some vertebrae (particularly where the neural spine is very subdued). In the absence of a line drawing, consider labeling parts of the figures. For instance, in Figure 4 the bifurcation of the neural spine is an important feature, but it is really hard for this non-sauropodologist to pick out the neural spine in some of the photos. In figure 6, it is really hard to pick out the prezygapophyseal facet. Etc.
- Figure 4. Include letter labels. This is far more intuitive than trying to pick out top and bottom specimens, etc.
- Figure 5. I appreciate the desire to illustrate this specimen (it is beautiful), but it is so minimally referenced in the text as to seem a little superfluous. Do you really need 6 views to get across the relevant points? Granted, I like things to be illustrated in detail, but it seems odd to have 6 views of a vertebra from a taxon that is only distantly related to Barosaurus.
- Does YPM 429 have a broader context? Where was it found? Which rock formation? As is, it is just dropped into the discussion, which not a lot of context. Given the later questions about association of the specimen, surely there must be some field notes at the YPM that talk about this. Or maybe not? Something to check into. Given the concerns about association, field data are critical. Were they found in the same quarry? This is mentioned in one part (p. 10), but then the whole issue of a quarry map is discarded for the section on association at p. 14. Are there other sauropods from the same site? These sort of data are critical, but not realy addressed at the appropriate points in the text.
- How do the AMNH and YPM Barosaurus compare in size? Are any measurements available for the AMNH specimen?
- The vertebral descriptions seem a little brief; rather than just calling out a few features, why not include a comprehensive redescription using modern terminology (which was not used by Lull or Marsh)? What are the shapes, orientations, etc., of the laminae? Of the pleurocoels? Some of these descriptions occur in some places, but I was really hoping for the definitive description of the cervical vertebrae of YPM 429. Maybe that's beyond the scope of the paper...but why not broaden the scope just a little? It would only improve the utility of the work to a broader audience!
- For AMNH 6341 vs. YPM 429, do you have any stratigraphic comparisons?Although morphology is primary, it would be important and interesting to know how these animals stack up to each other in geological time. Perhaps John Foster's thesis has some data that would be of help.
--Andrew A. Farke, 23 September 2013