Giant Bird Tracks (Family Gastornithidae) from the Paleogene Chuckanut Formation, Northwest Washington, USA, with a Review of Gastornis Distribution

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This article does a good job of reviewing the bird tracks from Washington and presents new data based on recent discoveries. It merits publication after minor revision--see my comments/edits in the pdf. The main content concern is the title, which really does not reflect the article content-- in addition to its presentation of the tracks from Washington, it provides a review of the distribution, taxonomy, paleoecology etc of Gastornis, so something about that should be in the title.

Comments for author File: Comments.pdf

Author Response

Thanks for the encouraging review. I have changed the title in accordance to your recommendation. I have also made the several edits suggested in the PDF review, including improving the quality of the captions for two figures.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This is a highly interesting paper providing important new ichnological information about the Paleogene giant bird Gastornis. The evidence is well presented with detailed information about the geology, stratigraphy and paleoenvironment of the localities. The trackways are well described and illustrated with the necessary measurements. I agree with the author's conclusions about the paleobiology of Gastornis. The discovery of footprints of a Gastornis chick is especially interesting since little is known about the growth of this giant bird. On the whole the paper is very convincing and should attract some attention.

To improve the paper, it would be good to provide more comments about two points:

- estimated speed of adult Gastornis on the basis of the newly discovered trackway. Although it is not long (3 footprints), would it be possible to estimate the walking speed of the bird, using one of the various equations that have been published to estimate speed from trackways, notably for bipedal dinosaurs and some birds ? Although the author convincingly suggests a slow walk, it would be very useful to have a quantitative estimate.

- estimated size of the Gastornis chick on the basis of the available footprints. Although the error margin may be relatively high, it should be possible to provide an estimate of the height of the chick by comparison with the dimensions of the adult prints and the height of the rather complete adult skeleton described by Matthew and Granger. This will not provide a precise individual age estimate for the chick, but it may suggest whether it was a very young bird or had already reached a certain age.

I have corrected various typos directly on the MS (see attached file).

Comments for author File: Comments.pdf

Author Response

Thanks for the keen-eyed proof reading. I have fixed all of the various typos that you discovered. In regards to larger issues, I prefer not to attempt to quantify a locomotion rate based on a trackway than contains only three footprints.  I have adopted your suggestion to estimate the size of the Gastornis chick based on track parameters. Thanks for that good idea.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Revision is fine and complete.

Reviewer 2 Report

Comments and Suggestions for Authors

Thank you for revising the paper. The trackway is indeed a little short to provide a reliable speed estimate. Congratulations for that really nice paper !