Résumé
Life evolution has been shaped by marine and continental environmental dichotomy. Particularly, the ecological history of vertebrates is divided into several aquatic and terrestrial phases. Even today, some species spend time in both marine and continental environments during their lifetime. Nevertheless, the timing and location of past ecological transitions, as well as the monitoring of current migration, are still challenging to trace. To reconstruct the aquatic environments of vertebrates (i.e. seawater vs freshwater), stable (delta (super 13) C, delta (super 18) O, delta (super 34) S) and radiogenic ( (super 87) Sr/ (super 86) Sr) isotope systems applied to mineralized tissues have been commonly used in the past decades (super 1-6) . Nevertheless, these methods hold some limitations as they cannot be applied universally. Here, we measured the lithium stable isotope composition of mineralized tissues (delta (super 7) Li) from extant vertebrates living in various aquatic environments (seawater, freshwater/terrestrial, and "transitional environments"). We highlight the potential of delta (super 7) Li to decipher vertebrates that live in these different environments, in contrast to delta (super 34) S and delta (super 18) O that cannot distinguish - in some cases - species living in intermediate waters from those living in seawater. Furthermore, we measured the delta (super 7) Li values of fossil apatites from extinct vertebrates and obtained values that fall within the range of aquatic environment of their extant relatives (super 7) . This new proxy may therefore profit studies in ecology, archaeology and palaeontology. 1. M. T. Clementz, A. Goswami, P. D. Gingerich and P. L. Koch, Journal of Vertebrate Paleontology, 2006, 26, 355-370. 2. J. Fischer, S. Voigt, M. Franz, J. W. Schneider, M. M. Joachimski, M. Tichomirowa, J. Goetze and H. Furrer, Palaeogeography, Palaeoclimatology, Palaeoecology, 2012, 353-355, 60-72. 3. J. Goedert, C. Lecuyer, R. Amiot, F. Arnaud-Godet, X. Wang, L. Cui, G. Cuny, G. Douay, F. Fourel, G. Panczer, L. Simon, J.-S. Steyer and M. Zhu, Nature, 2018, 558, 68-72. 4. J. Goedert, R. Amiot, D. Berthet, F. Fourel, L. Simon and C. Lecuyer, Sci Nat, 2020, 107, 10. 5. L. Kocsis, A. Osi, T. Vennemann, C. N. Trueman and M. R. Palmer, Palaeogeography, Palaeoclimatology, Palaeoecology, 2009, 280, 532-542. 6. B. Schmitz, S. L. Ingram, D. T. Dockery and G. Aberg, Chemical Geology, 1997, 140, 275-287. 7. F. Thibon, J. Goedert, N. Seon, L. Weppe, J. E. Martin, R. Amiot, S. Adnet, O. Lambert, P. Bustamante, C. Lecuyer and N. Vigier, Earth and Planetary Science Letters, 2022, 599, 117840. [Copyright Author(s) 2023. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]