Non-avian dinosaur eggshell calcite can contain ancient, endogenous amino acids
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Proteins are the most stable of the macromolecules that carry genetic information over long periods of time. Closed systems are more likely to retain endogenous proteins or their degradation products. Amino acid racemisation data in experimental and subfossil material suggests that mollusc shell and avian eggshell calcite crystals can demonstrate closed system behaviour, retaining endogenous amino acids. Here, Late Cretaceous (Campanian–Maastrichtian) Argentine titanosaurian sauropod eggshells show dark, organic stains under light microscopy/photography and fluorescence imaging. Raman spectroscopy can yield bands consistent with various organic molecules, possibly including N-bearing molecules or geopolymers. Pyrolysis-gas chromatography-mass spectrometry reveals pyrolysates consistent with amino acids as well as aliphatic hydrocarbon homologues that are not present in modern eggshell, consistent with kerogen formation deriving from eggshell lipids. High-performance liquid chromatography reveals that their intra-crystalline fraction can be enriched in some of the most stable amino acids (Glx, Gly, Ala, and possibly Val) and are fully racemic (despite being some of the slowest racemising amino acids), indicating ancient origin. This preservation varies across localities, but similar ancient amino acid profiles were also observed in Late Cretaceous Spanish titanosaurians from several localities and Chinese putative hadrosaurid eggshell. These amino acid results are consistent with previous studies on degradation trends deduced from modern, thermally matured, sub-fossil, and ∼3.8–6.5 Ma avian eggshell, as well as ∼30 Ma calcitic mollusc opercula. Selective preservation of certain fully racemic amino acids, which do not racemise in-chain, and the concentration of free amino acids suggests likely complete hydrolysis of original peptides. Liquid chromatography-tandem mass spectrometry supports this hypothesis by failing to detect any non-contamination peptide sequences from the Mesozoic eggshell. These closed-system amino acids are possibly the most thoroughly supported non-avian dinosaur endogenous protein-derived constituents, at least those that have not undergone oxidative condensation with other classes of biomolecules. Biocrystal matrices can help preserve mobile organic molecules by trapping them (perhaps with the assistance of resistant organic polymers), but trapped organics are nevertheless prone to diagenetic degradation, even if such reactions might be slowed in exceptional circumstances. Future work should survey fossil biocalcite to determine variability in amino acid preservation.
| Originalsprog | Engelsk |
|---|---|
| Tidsskrift | Geochimica et Cosmochimica Acta |
| Vol/bind | 365 |
| Sider (fra-til) | 1-20 |
| Antal sider | 20 |
| ISSN | 0016-7037 |
| DOI | |
| Status | Udgivet - 2024 |
Bibliografisk note
Funding Information:
We thank Jennika Greer (University of Chicago, Field Museum) for assistance in aseptic polishing of the eggshells that were not embedded in a matrix, Sheila Taylor (University of York) for assistance in preparing the samples for RP-HPLC, Matthew Von Tersch (University of York) for photographing the LACM specimens, Erzsebet Thornberry (University of Bristol) for assistance in Py-GC-MS data analysis, Claudia Hildebrandt (University of Bristol) for assistance in polarized light microscopy, and Jesper Velgaard Olsen (Novo Nordisk Center for Protein Research, University of Copenhagen) for providing MS access and resources. Work supported by the University of Bristol Bob Savage Memorial Fund and the Leverhulme Trust (PLP-2012-116). We thank Maureen Walsh, Luis Chiappe, and Lina Candrella of the Natural History Museum of Los Angeles County for access to Auca Mahuevo specimens. We thank Rodolfo Coria (Universidad Nacional de Río Negro), Leonardo Salgado (Universidad Nacional de Río Negro), Juliana Sterli (Museo Paleontológico Egidio Feruglio), Pablo Tubaro (Museo Provincial Patagónico de Ciencias Naturales), Gabriela Costanzo, Ernesto Rodrigo Paz, José Luis Garrido, Asociación Paleontológica Argentina, and National Authority of the Application of the Law of Paleontological Heritage for assisting in our efforts to repatriate the independently acquired M. megadermus specimens to Argentina. We also thank two anonymous reviewers and the editors Robert Asher (University of Cambridge), Jérémy Anquetin (Jurassica Museum), and Guillaume Billet (Muséum national d'Histoire naturelle) at PCI Paleo for helpful comments on our previously drafted preprint. Finally, we thank three anonymous reviewers that commented upon the manuscript as published here. Gallus gallus domesticus (Public Domain Dedication 1.0, https://creativecommons.org/publicdomain/zero/1.0/legalcode), Struthio camelus (Lukasiniho, Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported, https://creativecommons.org/licenses/by-nc-sa/3.0/legalcode, CC BY-NC-SA 3.0), hadrosaur (Iain Reid, Attribution 3.0 Unported, https://creativecommons.org/licenses/by/3.0/legalcode, CC BY 3.0), and titanosaurians (T. Tischler, Creative Commons Attribution-ShareAlike 3.0 Unported, https://creativecommons.org/licenses/by-sa/3.0/legalcode, CC BY-SA 3.0; Ryan Santos Soledade, CC0 1.0 Universal Public Domain Dedication, https://creativecommons.org/publicdomain/zero/1.0/legalcode; Scott Hartman, Attribution-NonCommercial-ShareAlike 3.0 Unported, https://creativecommons.org/licenses/by-nc-sa/3.0/legalcode, CC BY-NC-SA 3.0) silhouettes were obtained from phylopic.org with some color modifications. Research data has been supplied via a repository: https://doi.org/10.6084/m9.figshare.23784300.
Funding Information:
We thank Jennika Greer ( University of Chicago , Field Museum) for assistance in aseptic polishing of the eggshells that were not embedded in a matrix, Sheila Taylor ( University of York ) for assistance in preparing the samples for RP-HPLC , Matthew Von Tersch (University of York) for photographing the LACM specimens, Erzsebet Thornberry (University of Bristol) for assistance in Py-GC-MS data analysis, Claudia Hildebrandt ( University of Bristol ) for assistance in polarized light microscopy, and Jesper Velgaard Olsen ( Novo Nordisk Center for Protein Research, University of Copenhagen ) for providing MS access and resources. Work supported by the University of Bristol Bob Savage Memorial Fund and the Leverhulme Trust (PLP-2012-116). We thank Maureen Walsh, Luis Chiappe, and Lina Candrella of the Natural History Museum of Los Angeles County for access to Auca Mahuevo specimens. We thank Rodolfo Coria ( Universidad Nacional de Río Negro ), Leonardo Salgado (Universidad Nacional de Río Negro), Juliana Sterli (Museo Paleontológico Egidio Feruglio), Pablo Tubaro (Museo Provincial Patagónico de Ciencias Naturales), Gabriela Costanzo, Ernesto Rodrigo Paz, José Luis Garrido, Asociación Paleontológica Argentina, and National Authority of the Application of the Law of Paleontological Heritage for assisting in our efforts to repatriate the independently acquired M. megadermus specimens to Argentina. We also thank two anonymous reviewers and the editors Robert Asher ( University of Cambridge ), Jérémy Anquetin (Jurassica Museum), and Guillaume Billet (Muséum national d’Histoire naturelle) at PCI Paleo for helpful comments on our previously drafted preprint. Finally, we thank three anonymous reviewers that commented upon the manuscript as published here. Gallus gallus domesticus (Public Domain Dedication 1.0, https://creativecommons.org/publicdomain/zero/1.0/legalcode ), Struthio camelus (Lukasiniho, Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported, https://creativecommons.org/licenses/by-nc-sa/3.0/legalcode , CC BY-NC-SA 3.0 ), hadrosaur (Iain Reid, Attribution 3.0 Unported, https://creativecommons.org/licenses/by/3.0/legalcode , CC BY 3.0 ), and titanosaurians (T. Tischler, Creative Commons Attribution-ShareAlike 3.0 Unported, https://creativecommons.org/licenses/by-sa/3.0/legalcode , CC BY-SA 3.0 ; Ryan Santos Soledade, CC0 1.0 Universal Public Domain Dedication, https://creativecommons.org/publicdomain/zero/1.0/legalcode ; Scott Hartman, Attribution-NonCommercial-ShareAlike 3.0 Unported, https://creativecommons.org/licenses/by-nc-sa/3.0/legalcode , CC BY-NC-SA 3.0 ) silhouettes were obtained from phylopic.org with some color modifications.
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