Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Matters Arising
  • Published:

Reply to: Triassic sauropodomorph eggshell might not be soft

Nature volume 610, pages E11–E14 (2022)Cite this article

Subjects

The Original Article was published on 19 October 2022

replying to S. Choi et al. Nature https://doi.org/10.1038/s41586-022-05151-9 (2022)

In the accompanying Comment, Choi et al.1 dispute morphological, histological, geochemical and biomechanical evidence for a soft-shelled egg in Mussaurus2, an Early Jurassic sauropodomorph, based on three main assertions, namely that: (1) the carbonate signal associated with Mussaurus eggshell could represent original biomineral, despite its chemical and petrographic resemblance to the limy sediment matrix; (2) the endogenous N-, O- and S-heterocyclic polymers, which generate the Mussaurus egg morphology and encode the biomineralization signal, might represent sedimentary kerogen (refuted in figure 2a of ref. 2) or graphitic carbon, which cannot possibly form under the pressure and temperature conditions in question3; (3) birefringence, which would indicate eggshell calcite, may be obscured in the thin section by organic matter (contra the previous claim suggesting only graphite might be preserved). Choi et al.1 disagree with our analyses of the Mussaurus eggshell while ignoring the biomechanical evidence and compound maps presented in Norell et al.2 and accepting identical analyses for the Protoceratops eggshell1. Choi et al.1 did not perform new analyses, but scored the Mussaurus eggshell as hard on the basis of comparisons with hard-shelled but unrelated non-dinosaurian eggshell (Aenigmaoolithus) from a dissimilar age, region and volcanic setting4. They re-ran our ancestral state reconstruction without time scaling and obtained an ambiguous 52% probability of hard-shelled eggs in the ancestral dinosaur, in contrast to our inference of an ancestrally soft egg2.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: The geochemistry of Mussaurus eggshell.

Data availability

All relevant data are available in the paper and Supplementary Data 1 and 2, the original paper2 and ref. 12.

Code availability

R code used for the ancestral state reconstruction is available as Supplementary Code.

References

  1. Choi, S., Yang, T.-R., Moreno-Azanza, M., Zhang, S. & Kim, N.-H. Triassic sauropodomorph eggshell might not be soft. Nature https://doi.org/10.1038/s41586-022-05151-9 (2022).

  2. Norell, M. A. et al. The first dinosaur egg was soft. Nature 583, 406–410 (2020).

    Article  ADS  CAS  Google Scholar 

  3. Buseck, P. R. & Beyssac, O. From organic matter to graphite: graphitization. Elements 10, 421–426 (2014).

    Article  CAS  Google Scholar 

  4. Choi, S., Lee, S. K., Kim, N. H., Kim, S. & Lee, Y. N. Raman spectroscopy detects amorphous carbon in an enigmatic egg from the Upper Cretaceous Wido Volcanics of South Korea. Front. Earth Sci. 7, 349 (2020).

    Article  ADS  Google Scholar 

  5. Chave, K. E. Carbonates: association with organic matter in surface seawater. Science 148, 1723–1724 (1965).

    Article  ADS  CAS  Google Scholar 

  6. Suess, E. Interaction of organic compounds with calcium carbonate. I. Association phenomena and geochemical implications. Geochim. Cosmochim. Acta 34, 157–168 (1970).

    Article  ADS  CAS  Google Scholar 

  7. Borromeo, L. et al. Raman spectroscopy as a tool for magnesium estimation in Mg‐calcite. J. Raman Spectrosc. 48, 983–992 (2017).

    Article  ADS  CAS  Google Scholar 

  8. Wiemann, J., Crawford, J. M. & Briggs, D. E. Phylogenetic and physiological signals in metazoan fossil biomolecules. Sci. Adv. 6, eaba6883 (2020).

    Article  ADS  CAS  Google Scholar 

  9. Lafuente, B., Downs, R. T., Yang, H. & Stone, N. in Highlights in Mineralogical crystallography (eds Armbruster, T. & Danisi, R. M.) Ch. 1, 1–30 (De Gruyter, 2015).

  10. Mikhailov, K. E. Classification of fossil eggshells of amniotic vertebrates. Acta Palaeontol. Pol. 36, 21–39 (1991).

  11. Wiemann, J. & Briggs, D. E. G. Raman spectroscopy is a powerful tool in molecular paleobiology: an analytical response to Alleon et al. BioEssays 44, 2100070 (2022).

    Article  Google Scholar 

  12. Wiemann, J. et al. Fossilization transforms vertebrate hard tissue proteins into N-heterocyclic polymers. Nat. Commun. 9, 4741 (2018).

    Article  ADS  Google Scholar 

  13. Anthony, J. W., Bideaux, R. A., Bladh, K. W. & Nichols, M. C. Handbook of Mineralogy: Volume I. Elements, Sulfides, Sulfosalts (Mineral Data Pub., 1990).

  14. Stein, K. et al. Structure and evolutionary implications of the earliest (Sinemurian, Early Jurassic) dinosaur eggs and eggshells. Sci. Rep. 9, 4424 (2019).

    Article  ADS  Google Scholar 

  15. Legendre, L. J. et al. A giant soft-shelled egg from the Late Cretaceous of Antarctica. Nature 583, 411–414 (2020).

    Article  ADS  CAS  Google Scholar 

  16. Bapst, D. W. paleotree: an R package for paleontological and phylogenetic analyses of evolution. Methods Ecol. Evol. 3, 803–807 (2012).

    Article  Google Scholar 

  17. Revell, L. J. phytools: an R package for phylogenetic comparative biology (and other things). Methods Ecol. Evol. 3, 217–223 (2012).

    Article  Google Scholar 

  18. Paradis, E. & Schliep, K. ape 5.0: an environment for modern phylogenetics and evolutionary analyses in R. Bioinformatics 35, 526–528 (2019).

    Article  CAS  Google Scholar 

  19. Harmon, L. J. et al. GEIGER: investigating evolutionary radiations. Bioinformatics 24, 129–131 (2008).

    Article  CAS  Google Scholar 

Download references

Acknowledgements

We thank D. E. G. Briggs for helpful comments and edits. J. O’Connor and P. Heck offered laboratory and instrument access. A. Shinya prepared the new thin section and G. Olack helped to collect the elemental maps. I.M. was funded by project no. PGC2018-094955-A-I00 granted by the Spanish Ministerio de Ciencia, Innovación y Universidades.

Author information

Authors and Affiliations

  1. Division of Paleontology, American Museum of Natural History, New York, NY, USA

    Mark A. Norell & Congyu Yu

  2. Department of Earth and Planetary Sciences, Yale University, New Haven, CT, USA

    Jasmina Wiemann & Matteo Fabbri

  3. Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA

    Jasmina Wiemann

  4. Departamento de Geodinámica, Estratigrafía y Paleontología, Facultad de Ciencias Geológicas, Universidad Complutense de Madrid, Madrid, Spain

    Iris Menéndez

  5. Departamento de Cambio Medioambiental, Instituto de Geociencias (UCM, CSIC), Madrid, Spain

    Iris Menéndez

  6. Negaunee Integrative Research Centre, Field Museum of Natural History, Chicago, IL, USA

    Matteo Fabbri

  7. Departamento de Ciencias Geológicas, Universidad de Buenos Aires, Buenos Aires, Argentina

    Claudia A. Marsicano

  8. Earth Sciences, Montana State University, Bozeman, MT, USA

    Anita Moore-Nall & David J. Varricchio

  9. CONICET, Museo Paleontológico Egidio Feruglio, Trelew, Argentina

    Diego Pol

  10. Department of Geoscience, University of Calgary, Calgary, Alberta, Canada

    Darla K. Zelenitsky

Authors
  1. Mark A. Norell
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Jasmina Wiemann
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Iris Menéndez
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Matteo Fabbri
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Congyu Yu
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Claudia A. Marsicano
    View author publications

    You can also search for this author in PubMed Google Scholar

  7. Anita Moore-Nall
    View author publications

    You can also search for this author in PubMed Google Scholar

  8. David J. Varricchio
    View author publications

    You can also search for this author in PubMed Google Scholar

  9. Diego Pol
    View author publications

    You can also search for this author in PubMed Google Scholar

  10. Darla K. Zelenitsky
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

J.W. collected and analysed in situ Raman microspectroscopy data, prepared Fig. 1 and wrote, together with D.K.Z., M.F. and I.M. the first draft of the manuscript. M.F. collected elemental maps and imaged the new thin section. I.M. performed the time-scaled ancestral state reconstruction and prepared Extended Data Fig. 1. All authors contributed to the discussion of the data and the final version of the manuscript.

Corresponding authors

Correspondence to Jasmina Wiemann, Iris Menéndez or Matteo Fabbri.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data figures and tables

Extended Data Fig. 1 Time-scaled ancestral state reconstruction of diapsid eggshell evolution with the status of Mussaurus eggs changed to ‘hard-shelled’ despite evidence for its soft nature.

Time scaling of the tree2 (100 times) was performed in the R16 ‘paleotree’ package. Branch scaling: stratigraphic appearance of each taxon (minimum and maximum age); node calibration: minimum age of clade appearance. The consensus tree was calculated using consensus.edges in R ‘phytools’17. Model: maximum likelihood (ML: ace in ‘ape’18). fitdiscrete in the R package ‘geiger’19 was used to determine ARD (= all rates differ) as the best transition model (ER; SYM; ARD). Node numbers and state probabilities can be found in the Supplementary Data 2.

Supplementary information

Supplementary Data 1

All spectroscopy-related data.

Supplementary Data 2

Ancestral state reconstruction.

Supplementary Code

Source code containing the R script.

Reporting Summary

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Norell, M.A., Wiemann, J., Menéndez, I. et al. Reply to: Triassic sauropodomorph eggshell might not be soft. Nature 610, E11–E14 (2022). https://doi.org/10.1038/s41586-022-05152-8

Download citation

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/s41586-022-05152-8

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Search

Advanced search

Quick links

Nature Briefing Microbiology

Sign up for the Nature Briefing: Microbiology newsletter — what matters in microbiology research, free to your inbox weekly.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing: Microbiology