Mechanistic Thermal Modeling of Late Triassic Terrestrial Amniotes Predicts Biogeographic Distribution

Round 1

Reviewer 1 Report

Based on the work of [35], the Mean Annual Temperature was 23~29 C for Late Triassic at Utah, and semiarid to subhumid conditions. If you use this one, the temperature range should be beyond 10~40C based on current knowledge, similar to temperature range used in [14] (Cold: 16–30˚C; warm: 20–34˚C; hot: 26–40˚C), not 21-31 C you used. For high latitudes (I am not sure what is the range?>60 ), the lowest temperature should below 0 C as the recent work of Olsen et al. 2022. So your 14~24 C is totally wrong!

Olsen et al., 2022 Arctic ice and the ecological rise of the dinosaurs | Science Advances

 [61] You cited this as the reference for the cloud cover, but I do not get how do you get 50-90% as the range?

The hairs in the Permian coprolites are still controversial, but no one I know think dicynodonts with fur. But your treat of Placeria is correct.

 The only body fossil of a Triassic mammaliaforme is from the poorly-known docudont Tikitherium

Wrong. This genus is known by one single tooth. Morganucodon is the best known mammaliforms from Late Triassic (>205Ma), and it is no problem to use its skeleton even known from the Early Jurassic.

which survived until the mid-Late Triassic [70,71].  I don’t think ref. [71] is related here.

Fig.3  the weight of Mammaliaforme (cf. Morganucodon) is totally wrong. They are generally 100g. This group is small, cannot reach 1kg until much later.

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Reviewer 2 Report

This is a well conducted and interesting study. Despite their complexity, the text is clear,  with extensive description of all the methodological issues. I have only a couple of minor points that can be easily improved.

Fig. 4. I can’t see which panel is A and which one is B. It is clear from the text that 4a (text) and A (legend) are upper panel, and 4b and B are lower panel, but once labels A-B are used, they must be specified in the figure itself. Same for figures 5 and 6: just add labels A and B or don’t use they in the text (a mention to upper and lower panels in figure legends should be enough). It is 0k in Fig 7.

Fig 7 and related text. To avoid confusion, perhaps it’s better to use torpor throughout this section instead of hibernation. Obviously both hibernation and torpor are compatible with burrowing, but here you refer explicitly to torpor. Therefore, change “Impact of modeling hibernation on ME plots” to “Impact of modeling torpor on ME plots”, and thus no further explanation (“Note this behaviour …”) is needed.

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Reviewer 3 Report

This is a compelling and exciting research avenue. I was impressed with how the complex thermal modeling the authors used complemented known data (anatomy, inferred behavior, biogeography) on the fossil organisms in question. 

However, many of the most important model inputs regarding the biology of extinct animals is at best uncertain: BMR, integument, etc. The authors are candid here, but even so there are some issues. I also want to commend the authors on including so many very different kinds of Triassic organisms in their study. That is not without its difficulties though, and I recommend several substantial revisions or reframings. 

For example: I am uncomfortable with the Mammaliaformes input as a small Jurassic taxon scaled up based on a single controversial Triassic tooth when several other candidate cynodonts might be more appropriate. Similarly, our understanding of lagerpetid ornithodirans has also evolved substantially over the last couple years, and it would serve the authors to reconsider the heavy lean into lagerpetid burrowing hypotheses. 

Generally, the wide taxonomic scope of the work means that there are many quibbles to be reconciled, & nuance and clarifications to add. 

This work is impressive and quite novel. There is a reason there is so much to pick at! I think the authors are usually appropriately conservative in their interpretations.

Please see my attached detailed file for line-by-line edits, questions, and suggestions.

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Round 2

Reviewer 1 Report

I think your paper is interesting for using detailed model to calculate the distribution of tetrapods. I think most of the result are soundable. However, I am not quite understand how did your select your parameters, especially the temperature. Did you only choose the temperature for one month or all range? Or it is Mean annual temperature? For me, the upper and lower bound of the temperature really controlled the distribution of life, so you need use the real temperature range. Your range is different from what I read from table S1, which I think is accepetable except for the high latitude. 

Prochnow et al. (2006) stated the MAT within Chile Formation was 23 to 29, really corresponding the tropical zone.

Sellwood et al. (2006)

“Continental regions between about 40°N and S are generally warm (>20 °C) throughout the year but have sustained highs into the 30s and 40s during most of the year.”

For arid zones of same latitute, the temperature variation should be wider than tropical zone.

I checked your Table S1, you really use 41 as your high temperature, but the lower bound for the high latitudes is 14. For high latitude, 14~24°C is problematic, it is possibly only within the summer; winter is much colder.  One thing is you need state tetrapods cannot active during T<14, they either migrated or hibernated (so burrowing).

 Although cloud cover were insignificant in the model. Your citation on could cover [Parrish (1993)] is not correct. I do not know your source, but 50-90% cannot applied to Arid zone, it may be correct for tropical zone and warm temperate zone. 

Olsen et al. 2022 result is not strange, Landwehrsetal. (2020) modeled same result, “significant sea ice is present north of 60°N”. In Siberia, T<-20°C.

For your result, “Looking at the results of low latitude Late Triassic microclimates [14,37] there is little difference in thermal performance between the monsoon and arid environments”

Did you test use different temperature range for them? I cannot get it. If you really test for diffrent T ranges, it is ok.

For Fig. 14, it is hard to differentiate different colors, you can use different shapes or letters.

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Reviewer 3 Report

I commend the authors for quickly and fully responding to my comments, criticisms, and suggestions. There are still some small quibbles, but the manuscript is greatly improved. I think the lagerpetid section is much better suited to our current understanding, and I applaud the switch to Tritylodon for the mammaliamorph input. 

Two very small errors: 1) in the abstract mammaliamorph is misspelled; 2) Figure 3D I think there is a typo in the legend and it is meant to read "Desmatosuchus (based on the skeleton of Stagonolepis)"

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Round 3

Reviewer 1 Report

As you said in reply, it is better specific how your modeled range is selected, and it is not the real temperature range.  The test models are still far from the real work.

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