Collaborative Research: Biogeochemical Fingerprinting of the Megatoothed ("Megalodon") Shark: A Dual Study in Thermophysiological Evolution and Seawater Chemistry

合作研究：巨齿鲨（“巨齿鲨”）的生物地球化学指纹：热生理进化和海水化学的双重研究

• 批准号: 1830581
• 负责人: Michael Griffiths
• 金额: $ 25.76万
• 依托单位: William Paterson University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-09-01 至 2022-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1830581&HistoricalAwards=false
• 关键词: Collaborative; Research; Biogeochemical; Fingerprinting; Megatoothed

The biology of iconic megatoothed 'megalodon' shark-the largest shark species to have existed on Earth-and other extinct sharks remain largely unknown. For example, it is unclear whether 'megalodon' was 'cold blooded' or 'warm blooded' and how other fossil shark species compare. Understanding these biological details coupled with environmental reconstructions could help researchers understand what led to the demise of 'megalodon' during the late Pliocene (about 2.6 million years ago), and thus help to better understand the sensitivity of large shark species to ecosystem changes. This project uses isotopic 'fingerprinting' of teeth to reconstruct not only the body temperatures, but also dietary behavior and seawater chemistry of 'megalodon' and other shark species during the past 15 million years. In addition, this work supports a PhD student, a postdoctoral research fellow at a Hispanic Serving Institution, and undergraduate research experiences for under-represented minority (URM) students. Shark teeth are the most abundant vertebrate fossil and their resistance to diagenetic alteration provides a substrate for gechemical analysis. This project explores the phylogenetic history of endothermy within lamniform sharks using a coupled paleoecological and geochemical framework. Specifically, this work consists of four objectives: (1) estimate body temperatures of modern and ancestral marine vertebrates using 'clumped' isotope thermometry (i.e., thermodynamic preference of 13C and 18O to form bonds, or 'clump', in the carbonate mineral lattice), and assess foraging behavior using calcium isotopes (44Ca/42Ca) and 3D microwear analysis in bioapatite; (2) reconstruct and compare shark habitats using oxygen isotopes ( 18O) of shark tooth phosphate and carbonate; (3) infer changes in seawater Sr/Ca between the mid-Miocene Climate Optimum (17-15 million years before present) and Pliocene (~5.3-2.6 million years before present) from bioapatite; (4) build a research community of under-represented minority students. Coupling 'clumped' isotope thermometry-a relatively new method to determine body temperature-with other stable isotope and biogeochemical proxies to explore shark paleoecology through geologic time is the first of its kind. In addition, this project coincides with an upsurge of interest in the debate surrounding the rise and extinction of 'megalodon.' This research, therefore, combines paleontological questions with geochemical techniques to bring scientists one step closer to tackling the 'megalodon extinction hypothesis'.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

标志性的巨齿鲨——地球上最大的鲨鱼物种——的生物学和其他灭绝的鲨鱼在很大程度上仍然未知。例如，目前还不清楚“巨齿鲨”是“冷血动物”还是“温血动物”，以及其他鲨鱼化石物种的比较情况。了解这些生物细节，再加上环境重建，可以帮助研究人员了解上新世晚期（约260万年前）“巨齿鲨”灭绝的原因，从而有助于更好地了解大型鲨鱼物种对生态系统变化的敏感性。该项目利用牙齿的同位素“指纹图谱”，不仅重建了体温，还重建了“巨齿鲨”和其他鲨鱼物种在过去1500万年中的饮食行为和海水化学。此外，这项工作还支持一名博士研究生，一名西班牙裔服务机构的博士后研究员，以及为代表性不足的少数民族（URM）学生提供本科研究经验。鲨鱼牙齿是最丰富的脊椎动物化石，它们对成岩蚀变的抵抗力为化学分析提供了基础。本项目利用古生态和地球化学相结合的框架探讨板形鲨鱼的恒温动物系统发育历史。具体来说，这项工作包括四个目标：(1)使用“团块”同位素测温法（即13C和18O在碳酸盐矿物晶格中形成键或“团块”的热力学偏好）估计现代和祖先海洋脊椎动物的体温，并使用钙同位素（44Ca/42Ca）和生物磷灰石的3D微磨损分析评估捕食行为；(2)利用鲨齿磷酸盐和碳酸盐的氧同位素（18O）重建和比较鲨鱼栖息地；(3)利用生物磷灰石推测中中新世（距今1700万年~ 1500万年）至上新世（距今约530万年~ 260万年）间海水Sr/Ca的变化；(4)建立一个由代表性不足的少数民族学生组成的研究社区。将“团块”同位素测温法——一种相对较新的测定体温的方法——与其他稳定的同位素和生物地球化学代理相结合，通过地质时间来探索鲨鱼的古生态，这是同类方法中的第一个。此外，这个项目恰逢人们对“巨齿鲨”的兴起和灭绝争论的兴趣高涨。因此，这项研究将古生物学问题与地球化学技术结合起来，使科学家更接近解决“巨齿鲨灭绝假说”。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Revisiting body size trends and nursery areas of the Neogene megatooth shark, Otodus megalodon (Lamniformes: Otodontidae), reveals Bergmann’s rule possibly enhanced its gigantism in cooler waters

• DOI: 10.1080/08912963.2022.2032024
• 发表时间: 2022-03
• 期刊: Historical Biology
• 影响因子: 1.4
• 作者: K. Shimada;Harry M. Maisch;Victor J. Perez;Martin A Becker;M. Griffiths

Macroborings in Otodus megalodon and Otodus chubutensis shark teeth from the submerged shelf of Onslow Bay, North Carolina, USA: implications for processes of lag deposit formation

美国北卡罗来纳州昂斯洛湾水下陆架中巨齿鲨和楚布特齿鲨牙齿的宏观钻孔：对滞后沉积物形成过程的影响

• DOI: 10.1080/10420940.2019.1697257
• 发表时间: 2020
• 期刊: Ichnos
• 影响因子: 0.8
• 作者: Maisch, Harry M.;Becker, Martin A.;Chamberlain, John A.
• 通讯作者: Chamberlain, John A.

Chondrichthyans from the Lower Clayton Limestone Unit of the Midway Group (Paleocene) near Malvern, Arkansas, USA, with comments on the K/Pg boundary

来自美国阿肯色州马尔文附近中途岛群（古新世）下克莱顿石灰岩单元的软骨鱼，以及对 K/Pg 边界的评论

• DOI: 10.1007/s12542-019-00494-7
• 发表时间: 2019
• 期刊: PalZ
• 影响因子: 1.8
• 作者: Maisch, Harry M.;Becker, Martin A.;Griffiths, Michael L.
• 通讯作者: Griffiths, Michael L.

A record of the δ44/40Ca and [Sr] of seawater over the last 100 million years from fossil elasmobranch tooth enamel

过去 1 亿年软骨鱼牙釉质化石中海水的 δ44/40Ca 和 [Sr] 记录

• DOI: 10.1016/j.epsl.2020.116354
• 发表时间: 2020
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: Akhtar, Alliya A.;Santi, Lauren M.;Griffiths, Michael L.;Becker, Martin;Eagle, Robert A.;Kim, Sora;Kocsis, László;Rosenthal, Yair;Higgins, John A.
• 通讯作者: Higgins, John A.

Fossil fishes from a lag deposit within the Upper Cretaceous Mancos Shale in New Mexico, USA, with comments on correlative Turonian–Coniacian time-transgressive lags in the Western Interior Seaway of North America

美国新墨西哥州上白垩统曼科斯页岩滞后沉积物中的鱼类化石，以及对北美西部内海航道相关土伦阶-康尼亚阶时间海侵滞后的评论

• DOI: 10.1016/j.cretres.2021.104886
• 发表时间: 2021
• 期刊: Cretaceous Research
• 影响因子: 2.1
• 作者: Maisch, Harry M.;Becker, Martin A.;Shimada, Kenshu
• 通讯作者: Shimada, Kenshu