NSF Org:	EAR Division Of Earth Sciences
Recipient:	UNIVERSITY OF CALIFORNIA, LOS ANGELES
Initial Amendment Date:	August 14, 2018
Latest Amendment Date:	August 14, 2018
Award Number:	1830638
Award Instrument:	Standard Grant
Program Manager:	Dena Smith-Nufio dmsmith@nsf.gov  (703)292-7431 EAR  Division Of Earth Sciences GEO  Directorate for Geosciences
Start Date:	September 1, 2018
End Date:	August 31, 2021 (Estimated)
Total Intended Award Amount:	$72,430.00
Total Awarded Amount to Date:	$72,430.00
Funds Obligated to Date:	FY 2018 = $72,430.00
History of Investigator:	Robert Eagle (Principal Investigator) robeagle@g.ucla.edu
Recipient Sponsored Research Office:	University of California-Los Angeles 10889 WILSHIRE BLVD STE 700 LOS ANGELES CA  US  90024-4200 (310)794-0102
Sponsor Congressional District:	36
Primary Place of Performance:	University of California-Los Angeles CA  US  90095-1406
Primary Place of Performance Congressional District:	36
Unique Entity Identifier (UEI):	RN64EPNH8JC6
Parent UEI:
NSF Program(s):	Sedimentary Geo & Paleobiology
Primary Program Source:	01001819DB NSF RESEARCH & RELATED ACTIVIT
Program Reference Code(s):	7459
Program Element Code(s):	745900
Award Agency Code:	4900
Fund Agency Code:	4900
Assistance Listing Number(s):	47.050

ABSTRACT

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.

PROJECT OUTCOMES REPORT

Disclaimer

This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.

Otodus megalodon was a relative of great white sharks that went extinctaround 3.6 million years ago and could grow to the enormous size of at least 15 meters long, making it the largest apex marine predator since the extinction of the dinosaurs. Here we test hypotheses relating to its extinction by providing the first quantitative estimates of its body temperature, thereby constraining its thermal physiology. We found it had body temperatures significantly elevatedcompared to other sharks, consistent with it having a degree of internal heat production as modernwarm-blooded endotherms do. High metabolic costs associated with maintaining at least partialendothermy may have contributed to the vulnerability of this species to extinction compared to othershark species that persist until this day.

With collaborators we also examine the evolution of the trophic position of Otodus megalodon and related Otodus species through time, using two distinct proxies, based on N and Zn isotopes. The proxies showed that Otodus achived very high trophic positions - some of the highest recorded by these proxies. They also show that the high trophic level of Otodus species was reached in the oligocene period, with the shift beginning to high levels in the eocene. This work also illustrated the potential for trophic competition between Otodus and great white sharks in the Pliocene that may have been a contributing factor in Otodus extinction. 

Last Modified: 10/20/2022
Modified by: Robert Eagle

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