{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,27]],"date-time":"2026-06-27T07:12:37Z","timestamp":1782544357438,"version":"3.54.5"},"reference-count":49,"publisher":"National Academy of Sciences","issue":"33","license":[{"start":{"date-parts":[[2025,8,4]],"date-time":"2025-08-04T00:00:00Z","timestamp":1754265600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"}],"funder":[{"name":"German science foundation","award":["AP PA909\/20-1"],"award-info":[{"award-number":["AP PA909\/20-1"]}]},{"name":"DFG Heisenberg grant","award":["HE 6357\/4-1"],"award-info":[{"award-number":["HE 6357\/4-1"]}]},{"name":"VeWA consortium LOEWE program","award":["no. 681450"],"award-info":[{"award-number":["no. 681450"]}]}],"content-domain":{"domain":["www.pnas.org"],"crossmark-restriction":true},"short-container-title":["Proc. Natl. Acad. Sci. U.S.A."],"published-print":{"date-parts":[[2025,8,19]]},"abstract":"<jats:p>\n                    Air-breathing vertebrates incorporate a fraction of isotopically anomalous air O\n                    <jats:sub>2<\/jats:sub>\n                    in their body water. The\n                    <jats:sup>17<\/jats:sup>\n                    O isotope anomaly of air O\n                    <jats:sub>2<\/jats:sub>\n                    (expressed as \u0394\u2019\n                    <jats:sup>17<\/jats:sup>\n                    O\n                    <jats:sub>air<\/jats:sub>\n                    ) is related to atmospheric CO\n                    <jats:sub>2<\/jats:sub>\n                    concentrations (\n                    <jats:italic toggle=\"yes\">p<\/jats:italic>\n                    CO\n                    <jats:sub>2<\/jats:sub>\n                    ) and gross primary production (GPP). Tooth enamel records the \u0394\u2019\n                    <jats:sup>17<\/jats:sup>\n                    O of body water and can thus preserve such paleo-\n                    <jats:italic toggle=\"yes\">p<\/jats:italic>\n                    CO\n                    <jats:sub>2<\/jats:sub>\n                    or paleo-GPP information over geological time periods. Here, we demonstrate the potential of respective reconstructions of atmospheric\n                    <jats:italic toggle=\"yes\">p<\/jats:italic>\n                    CO\n                    <jats:sub>2<\/jats:sub>\n                    or GPP from the triple oxygen isotope composition of fossil dinosaur tooth enamel. The data from unaltered enamel samples, along with an assumed modern GPP\n                    <jats:sub>t<\/jats:sub>\n                    \/GPP\n                    <jats:sub>0<\/jats:sub>\n                    ratio of 1 for the Mesozoic, suggest a mean Late Jurassic\n                    <jats:italic toggle=\"yes\">p<\/jats:italic>\n                    CO\n                    <jats:sub>2<\/jats:sub>\n                    = 1,200 \u00b1 150 ppmv and Late Cretaceous\n                    <jats:italic toggle=\"yes\">p<\/jats:italic>\n                    CO\n                    <jats:sub>2<\/jats:sub>\n                    = 750 \u00b1 200 ppmv. These estimates are in good agreement with other\n                    <jats:italic toggle=\"yes\">p<\/jats:italic>\n                    CO\n                    <jats:sub>2<\/jats:sub>\n                    proxy data for the same time intervals. When utilizing a\n                    <jats:italic toggle=\"yes\">p<\/jats:italic>\n                    CO\n                    <jats:sub>2<\/jats:sub>\n                    inferred from other proxies, tooth enamel \u0394\u2019\n                    <jats:sup>17<\/jats:sup>\n                    O\n                    <jats:sub>PO4<\/jats:sub>\n                    may also serve as a proxy for GPP. Using published\n                    <jats:italic toggle=\"yes\">p<\/jats:italic>\n                    CO\n                    <jats:sub>2<\/jats:sub>\n                    data, we reconstructed GPP\n                    <jats:sub>t<\/jats:sub>\n                    \/GPP\n                    <jats:sub>0<\/jats:sub>\n                    ratios with 1.20 \u00b1 0.17 for the Late Jurassic and 2.24 \u00b1 0.96 for the Late Cretaceous, which would imply a 20 to 120% higher GPP in the Mesozoic than today. Overall, triple oxygen isotope analysis of fossil teeth of terrestrial amniotes can provide insights into past atmospheric greenhouse gas content and global primary productivity.\n                  <\/jats:p>","DOI":"10.1073\/pnas.2504324122","type":"journal-article","created":{"date-parts":[[2025,8,4]],"date-time":"2025-08-04T19:05:47Z","timestamp":1754334347000},"update-policy":"https:\/\/doi.org\/10.1073\/pnas.cm10313","source":"Crossref","is-referenced-by-count":5,"title":["Mesozoic atmospheric CO\n                    <sub>2<\/sub>\n                    concentrations reconstructed from dinosaur tooth enamel"],"prefix":"10.1073","volume":"122","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-1777-3136","authenticated-orcid":false,"given":"Dingsu","family":"Feng","sequence":"first","affiliation":[{"name":"Abteilung Geochemie & Isotopengeologie, Geowissenschaftliches Zentrum, Georg-August-Universit\u00e4t","place":["G\u00f6ttingen, Germany"]},{"name":"Institut f\u00fcr Geowissenschaften, Ruhr-Universit\u00e4t Bochum","place":["Bochum, Germany"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2590-8600","authenticated-orcid":false,"given":"Thomas","family":"T\u00fctken","sequence":"additional","affiliation":[{"name":"Institut f\u00fcr Geowissenschaften, AG Angewandte und Analytische Pal\u00e4ontologie, Universit\u00e4t Mainz","place":["Mainz, Germany"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2166-487X","authenticated-orcid":false,"given":"Eva Maria","family":"Griebeler","sequence":"additional","affiliation":[{"name":"Institut f\u00fcr Organismische und Molekulare Evolutionsbiologie, Universit\u00e4t Mainz","place":["Mainz, Germany"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3604-8295","authenticated-orcid":false,"given":"Daniel","family":"Herwartz","sequence":"additional","affiliation":[{"name":"Institut f\u00fcr Geowissenschaften, Ruhr-Universit\u00e4t Bochum","place":["Bochum, Germany"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2618-2768","authenticated-orcid":false,"given":"Andreas","family":"Pack","sequence":"additional","affiliation":[{"name":"Abteilung Geochemie & Isotopengeologie, Geowissenschaftliches Zentrum, Georg-August-Universit\u00e4t","place":["G\u00f6ttingen, Germany"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"341","published-online":{"date-parts":[[2025,8,4]]},"reference":[{"key":"e_1_3_4_1_2","doi-asserted-by":"publisher","DOI":"10.1080\/14786449608620846"},{"key":"e_1_3_4_2_2","first-page":"349","article-title":"Climate and atmospheric history of the past 420, 000 years from the Vostok ice core, Antarctica","volume":"54","author":"Petit J. 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