The first occurrence of the enigmatic archosaur Crosbysaurus (Heckert 2004) from the Chinle Formation of Southern Utah

Robert J Gay; Isabella St. Aude

doi:10.7287/peerj.preprints.537v1

The first occurrence of the enigmatic archosaur Crosbysaurus (Heckert 2004) from the Chinle Formation of Southern Utah

October 14, 2014

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Abstract

Originally identified as an ornithisichian dinosaur, Crosbysaurus has been found in New Mexico, Arizona, and the type locality in Texas, the genus has been reassessed by other workers in light of revelations about the postcrania of another putative Triassic ornithischian, Revueltosaurus. The understanding of Triassic dental faunas has become more complicated by the extreme convergence between pseudosuchian archosaurus and ornithichian dinosaur dental morphologies. This new specimen does not help resolve the affinities of Crosbysaurus but does extend the range of this taxon into southern Utah. This specimen may also represent the youngest-known member of this genus

Cite this as

Gay RJ, St. Aude I. 2014. The first occurrence of the enigmatic archosaur Crosbysaurus (Heckert 2004) from the Chinle Formation of Southern Utah. PeerJ PrePrints 2:e537v1 https://doi.org/10.7287/peerj.preprints.537v1

Author comment

This manuscript will be submitted to PeerJ for peer review. This study comes out of work described by the senior author in a poster to be presented at the 2014 SVP Annual Meeting in Berlin, Germany.

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Competing Interests

The authors declare they have no competing interests.

Author Contributions

Robert J Gay conceived and designed the experiments, performed the experiments, analyzed the data, contributed reagents/materials/analysis tools, wrote the paper, prepared figures and/or tables, reviewed drafts of the paper.

Isabella St. Aude performed the experiments, wrote the paper, reviewed drafts of the paper.

Data Deposition

The following information was supplied regarding the deposition of related data:

The poster describing the fieldwork and associated paleontology program will be archived on FigShare once it has been presented in Berlin in November.

Funding

This work was funded solely by student fundraising at Mission Heights Preparatory High School. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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3811 days ago - Andrew Farke

The specimen described here is sure to be of interest to many experts on Triassic terrestrial faunal assemblages. As currently written, the manuscript contains a nice, cohesive project, and many of the essential pieces of a thorough paper are here. However, I would recommend reorganization of the text, addition of a few other pieces of background information, and some revision of the figures, in order to maximize the readability and usability of the manuscript. Specific points are outlined in detail below.

Full disclosure: I am a volunteer editor for PeerJ, and also am co-presenting a paper for an upcoming scientific meeting with the senior author.

SPECIFIC COMMENTS:

- I would strongly advise reworking the abstract; there is lots of summary about Crosbysaurus, but very little on the specimen itself. You should include basic locality information, how it is referred to the taxon, etc. As it stands, the abstract is not particularly effective in summarizing the unique results of this study.

- The introduction might be restructured to improve readability and accessibility to most readers. I would start with a brief discussion of Crosbysaurus and the problems of Triassic "ornithischian" teeth, and perhaps include the current first paragraph somewhere in the middle, or else move it to the methods. The discovery narrative is good to include, but could perhaps be condensed a little.

- Where are the various institutions located? Cities, states, and countries should be included in the abbreviations list.

- Please include a basic geological background for the locality, in a concise paragraph or two. How old is the locality? What other fauna are known? What was the basic lithology? Where does it sit in section?

- I strongly recommend framing the description in a conventional "systematic paleontology" format. See, for example, https://peerj.com/articles/182/#results -- the standardized layout can make it easier for the typical paleontologist reader to navigate the paper and find the relevant information.

- How were measurements taken? Sliding calipers? Digital measurement? On what equipment were photos taken?

- In referring the tooth to Crosbysaurus, you should also mention why you do not refer it to similar tooth taxa. How is it different from Revueltosaurus, Tecovasaurus, etc.? A stronger differential diagnosis must be included.

- Conclusions: "Cosmopolitan" can be taken to mean spanning many countries, but Crosbysaurus is only found in the United States. Maybe use the term "widespread" instead?

- Acknowledgments should be under a separate heading.

- Because geographic range is such a big part of this paper's conclusions, I would include a figure (or modify Figure 1) showing the new find relative to other localities with Crosbysaurus.

- In Figure 2, the letters / lines added on the photo are hard to see in places. I would use light-colored drop lines/drop letters to help them stand out.

- Figure 3 should be redone; part 1 is quite blurry, and part 2 is not entirely in focus either. I might recommend coating the specimens for photography (e.g., ammonium chloride or a similar removable powder); color can obscure important morphology on teeth, and for this paper it is essential to have high-quality photographs. The lettering is really big relative to the teeth itself; I would scale the text on the figure down, to improve aesthetics. If possible, get a photo showing a close-up of the denticles drawn in Figure 5. This is a pretty key piece of anatomy and should be as well-illustrated as possible. Consider moving Figure 4 into part of Figure 3, so that it is alongside Figure 3C. This too would improve usability by the reader and ease comparisons between figures.

The first occurrence of the enigmatic archosaur Crosbysaurus (Heckert 2004) from the Chinle Formation of Southern Utah

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