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Posted by MSales on 03 Feb 2016 at 19:37 GMT
My colleagues and I are pleased by the fact that our new paper has attracted the attention of some readers. However, before addressing some comments, we’d like to advice the readers that some formatting errors occurred, especially regarding Tables 1-9, which may cause some confusion. Actually, PLOS ONE is already aware of such mistakes and working in order to fix them. At this moment, anyone can feel comfortable to contact me and get by e-mail the correct, original tables.
Now, regarding the suggestions of Christophe Hendrickx, we are in agreement with all the points raised by him. Our critics on some dubious theropod records were not developed because it was not the main point of our work, although it is an important assumption of it. In fact, we hope to eventually cover these questions in future studies. Also, it was a request that was made during the review process in order not to lengthen even more the text.
And, what about the impact of such occurrences over our results? Indeed, they could be responsible for “unreal” associations or their absence. However, such occurrences were not included in our Dataset IV (see S1 Dataset), which lacked all occurrences we judged as problematic. In fact, we assembled four sets of occurrences (our Datasets I-IV) and tested all of them. We did so in order to have a broader look on the caveats of this kind of analysis and better discuss our inferences. So, it is possible to see our results excluding the problematic occurrences checking the results for Dataset IV obtained by each test. In this regard, the formatting errors may be especially problematic, as I mentioned above.
With respect to the hypothetical scenario presented by our Fig 5 and based on two references (Buffetaut and Suteethorn, 1989, 1999), we also agree that it is impossible to rule out completely a hypothetical taphonomic process as the responsible for the association between the sauropod skeleton and the (here assumed) spinosaurid teeth. However, Fig 5, despite not being the main illustration of our work, does represent the hypothesis we favor in this discussion. We judge a trophic relationship (scavenging or predation) the most plausible explanation because it seems, in our view, to be the most parsimonious scenario in which these two distinct types of remains, regarding their transportability could be buried together. Laje do Coringa (Alcântara Formation, São Luís-Grajaú Basin), for instance, presents Cretaceous bone-beds with sauropod bones scattered among thousands of theropod teeth. However, the sauropod remains are mainly isolated elements that seem to have suffered reworking, which is a condition also found in the theropod teeth (Medeiros et al., 2007, 2014), contrasting to the sauropod partial skeleton in the Thai case. The preservation of teeth of a carnivorous animal along with the remains of a herbivore suggests a prey-predator relationship, although it is far from being a definitive clue. In addition, the Thai theropod teeth associated to the skeleton reported so far were not yet assigned to more than one morphotype that could be possibly attributed to more than one theropod taxon, which could be expected in a random deposition of teeth and bones. Again, Alcântara Fm. is also illustrative because anyone can easily find a carcharodontosaurid tooth along with another one of spinosaurid affinities and this pattern is seen throughout the outcrop. Although none of the points presented above is conclusive, taking all of them into account makes the taphonomic hypothesis the least probable one in our opinion. Furthermore, despite possessing piscivore-like teeth, there is no clear, insuperable ecological restriction that could make Siamosaurus (or whoever those teeth may belong to) to be a strictly piscivorous animal, similar to what was suggested by Therrien et al. (2007) for Suchomimus.
… But it’s science! As stated in our “Final Remarks”, we hope that our tests and assumptions propel future works, in particular, those on our dubious occurrences, mainly based on undescribed specimens. They may corroborate or refute our inferences, including the paleoecological scenario of Fig 5.
Marcos Sales, on behalf of all the authors
REFERENCES:
Buffetaut E, Suteethorn V. A sauropod skeleton associated with theropod teeth in the Upper Jurassic of Thailand: remarks on the taphonomic and palaeoecological significance of such associations. Palaeogeogr Palaeoclimatol Palaeoecol. 1989; 73: 77–83.
Buffetaut E, Suteethorn V. The dinosaur fauna of the Sao Khua Formation of Thailand and the beginning of the Cretaceous radiation of dinosaurs in Asia. Palaeogeogr Palaeoclimatol Palaeoecol. 1999; 150: 13–23.
Medeiros MA, Freire PC, Pereira AA, Santos RAB, Lindoso RM, Coêlho AFA, et al. Another African dinosaur recorded in the Eocenomanian of Brazil and a revision of the Laje do Coringa site. In: Carvalho IS, Cassab RCT, Schwanke C, Carvalho MA, Fernandes ACS, Rodrigues MAC, et al., editors. Paleontologia: Cenários de Vida. Vol. 1. Rio de Janeiro: Editora Interciência; 2007. p. 413–23.
Medeiros MA, Lindoso RM, Mendes ID, Carvalho IS. The Cretaceous (Cenomanian) continental record of the Laje do Coringa flagstone (Alcântara Formation), northeastern South America. J South Am Earth Sci. 2014; 53: 50–8.
Therrien F, Henderson DM, Ruff CB. Bite me: Biomechanical models of theropod mandibles and implications for feeding behavior. In: Carpenter K, editor. The Carnivorous Dinosaurs. Bloomington: Indiana University Press; 2005. p. 179–237.