What do fossils tell us about ancient marine ecosystems?


The evolution of ‘megatooth’ sharks, particularly the iconic Otodus megalodon, remains enigmatic despite recent paleontological advances. Central questions persist regarding the thermophysiological origins, environmental habitats, and paleodiets of these large predatory sharks and their fossil ancestors. These evolutionary details could elucidate the role of thermophysiology and dietary shifts in megatooth shark evolution since the Cretaceous, and help decipher the causes(s) for their ultimate extinction in megalodon during the Late Pliocene. Using novel biogeochemical proxies in both modern and fossil fish/shark teeth, our group is tackling some of these questions and uncertainties. Specific objectives of this research thus far are threefold:

(1) Estimate the body temperatures of modern and ancestral marine vertebrates using ‘clumped’ (13C-18O; ∆47) isotopes and phosphate δ18O (18O/16O) of elasmobranch tooth enameloid.

(Left) Modern Δ47–temperature calibration from wild-caught and aquarium-reared elasmobranch teeth, along with wild-caught bony fish and mammals. Lines indicate linear regressions calculated from our data (orange line and colored symbols) along with that of Anderson et al. (2021) (blue line). Shaded regions surrounding regression lines indicate 95% CI. Error bars in the x and y directions on symbols indicate uncertainty in temperature and one external SE of the average Δ47, respectively. Uncertainty in regression parameters indicates one SE. (Right) Body temperature reconstructions of O. megalodon, Mysticeti, and the Carcharodon lineage (C. hastalis and C. carcharias) from the eastern United States (North Carolina) and Japan from Δ47 (n = 53) and δ18Op (n = 39) for the Pliocene. Shark illustrations by Christina Spence Morgan, copyright 2021. Figure is an adaptation from Griffiths et al. (2023), Proceedings of the National Academy of Sciences.

(2) Unlock the paleo trophic-level habitats and food web dynamics of these predatory sharks using various other isotopic systems (δ66Zn, enamel-bound δ15N).

(3) Through combination of these isotope systems with analysis of elemental ratios (e.g., Sr/Ca) in the same teeth, infer changes in seawater chemistry through time.

Representative Publications

Enigmatic Carbonate Isotope Values in Shark Teeth: Evidence for Environmental and Dietary Controls.
Karnes, M.E., Chan, R.L., Kuntz, J.P., Griffiths, M.L., Shimada, K., Becker, M.A., Maisch IV, H.M., Eagle, R.A., Brenner-Coltrain, J., Miller, S., Kim, S.L., 2024. Palaeogeography, Palaeoclimatology, Palaeoecology 635, 111943.

Endothermic physiology of extinct megatooth sharks.
Griffiths, M.L., Eagle, R.A., Kim, S.L., Flores, R.J., Becker, M.A., Maisch IV, H.M., Trayler, R.B., Chan, R.L., McCormack, J., Akhtar, A.A. and Tripati, A.K., 2023. Proceedings of the National Academy of Sciences, 120(27), p.e2218153120. See associated Commentary.

Cenozoic megatooth sharks occupied extremely high trophic positions.
Kast, E.R., Griffiths, M.L., Kim, S.L., Rao, Z.C., Shimada, K., Becker, M.A., Maisch, H.M., Eagle, R.A., Clarke, C.A., Neumann, A.N., Karnes, M.E., Lüdecke, T., Leichliter, J.N., Martínez-García, A., Akhtar, A.A., Wang, X.T., Haug, G.H., Sigman, D.M., 2022. Science Advances 8, eabl6529. See associated Focus.

Trophic position of Otodus megalodon and great white sharks through time revealed by zinc isotopes.
McCormack, J., Griffiths, M.L., Kim, S.L., Shimada, K., Karnes, M., Maisch IV, H.M., Pederzani, S., Bourgon, N., Jaouen, K., Becker, M.A., Jons, N., Sisma-Ventura, G., Straube, N., Pollerspock, J., Hublin, J.J., Eagle, R.A., and Tutken, T., 2022. Nature Communications 13, 2980.

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.
Shimada, K., Maisch IV, H.M., Perez, V.J., Becker, M.A., and Griffiths, M.L., 2022. Historical Biology, 1-10.

Ontogenetic growth pattern of the extinct megatooth shark Otodus megalodon, and implications for its reproductive biology, development, and life expectancy.
Shimada, K., Bonnan, M.F., Becker, M.A., Griffiths, M.L., 2021. Historical Biology, 1-6.

Body, jaw, and dentition lengths of macrophagous lamniform sharks, and body size evolution in Lamniformes with special reference to ‘off-the-scale’ gigantism of the megatooth shark, Otodus megalodon.
Shimada, K., Becker, M.A. and Griffiths, M.L., 2020. Historical Biology, pp.1-17.

A record of the δ44/40Ca and [Sr] of seawater over the last 100 million years from fossil elasmobranch tooth enamel.
Akhtar, Alliya A., Santi, L.M., Griffiths, M.L., Becker, M., Eagle, R.A., Kim, S., Kocsis, L., Rosenthal, Y., and Higgins, J.A., 2020. Earth and Planetary Science Letters 543: 116354.

Chondrichthyans from the Lower Clayton Limestone Unit of the Midway Group (Paleocene) near Malvern, Arkansas, USA, with Comments on the K/Pg boundary.
Maisch IV, H.M., Becker, M.A., Griffiths, M.L., 2019. PalZ, DOI: 10.1007/s12542-019-00494-7.


Collaborative Research: Biogeochemical fingerprinting of the megatoothed (‘megalodon’) shark: a dual study in thermophysiological evolution and seawater chemistry [PI: M.L. Griffiths; co-PIs: M. Becker (WPU), Sora Kim (UC Merced), R. Eagle (UCLA), K. Shimada (DePaul University)] National Science Foundation, Sedimentary Geology and Paleobiology (SGP) EAR-7858820, $571,014 ($257,959 to Griffiths). 09/01/18 – 08/31/22.

Late Phanerozoic Evolution of Seawater Temperature and Sr/Ca: New Insights from “Clumped Isotope” Thermometry in Biogenic Apatite [PI: M.L. Griffiths]. American Chemical Society Petroleum Research Fund Undergraduate New Investigator Grant, PRF–#54852-UNI2, $55,000. 01/01/15 – 01/01/17.


Marty Becker, William Paterson University
Harry Maisch IV, Bergen Community College
Kenshu Shimada, DePaul University
Sora Kim, University of California, Merced
Robert Eagle, University of California, Los Angeles
John Higgins, Princeton University
Aradhna Tripati, University of California, Los Angeles
Elizabeth Sibert, Yale University
Yair Rosenthal, Rutgers University
Emma Kast, University of Cambridge
Danny Sigman, Princeton University
Jeremy McCormack, Max Planck Institute for Evolutionary Anthropology
Thomas Tütken, Johannes Gutenberg University of Mainz