Ancient marine isoscapes and isotopic evidence of bulk-feeding by Oligocene cetaceans

Mark T. Clementz; R. Ewan Fordyce; Stephanie L. Peek; David L. Fox

doi:10.1016/j.palaeo.2012.09.009

Ancient marine isoscapes and isotopic evidence of bulk-feeding by Oligocene cetaceans

Mark T. Clementz, R. Ewan Fordyce, Stephanie L. Peek, David L. Fox

Earth and Environmental Sciences-Twin Cities

Research output: Contribution to journal › Article › peer-review

52 Scopus citations

Abstract

The first appearance and evolution of the crown group Cetacea - Mysticeti (baleen whales) and Odontoceti (toothed whales and dolphins) - from archaeocete ancestors corresponds with major climatic and oceanographic changes shortly before the Eocene-Oligocene boundary (ca. 34.0Ma). These environmental changes impacted marine productivity and may have sparked the evolution of the distinct bulk-feeding strategy used by mysticete whales today. The movements and feeding habits of living cetaceans can be tracked using the isotopic composition of the structural carbonate within bioapatite of their bones and teeth, which records latitudinal gradients in marine δ¹³C and δ¹⁸O values. Here, we exploit this relationship to determine the past movements and feeding habits of late-surviving archaeocetes (kekenodontids) and early odontocetes and mysticetes sampled from Oligocene fossil sites in the USA (latitude: ~30°N) and New Zealand (latitude: ~50°S). Bioapatite δ¹³C and δ¹⁸O values for fossilized tooth enamel and bullae from fossil cetaceans were surprisingly similar to those for living cetaceans, which indicates that the feeding habits of these species and the isotopic composition of Oligocene seawater (ca. 28Ma) were very close to present-day conditions. Values for toothed mysticetes and odontocetes match expectations based on cetacean species feeding at these latitudes today, suggesting these individuals were residents that foraged in close proximity to where their fossils were discovered. In contrast, the extremely low δ¹³C and δ¹⁸O values for some edentulous mysticetes from New Zealand are more similar to values observed in extant mysticetes that seasonally migrate to high latitudes, where they bulk-feed on lipid-rich zooplankton. Enamel δ¹³C values for kekenodontids showed the greatest range and overlapped with both edentulous mysticetes and resident species; these differences correlate most strongly with tooth type and may reflect an ontogenetic shift in diet associated with the transition from nursing to marine prey. When combined with evidence of increasing morphological disparity, fossil bioapatite δ¹³C and δ¹⁸O values support interpretations that the Oligocene was an interval of heightened taxonomic and ecological diversification within Cetacea.

Original language	English (US)
Pages (from-to)	28-40
Number of pages	13
Journal	Palaeogeography, Palaeoclimatology, Palaeoecology
Volume	400
DOIs	https://doi.org/10.1016/j.palaeo.2012.09.009
State	Published - Apr 15 2014

Bibliographical note

Funding Information:
We thank the following curators and collection managers who provided us access to and assistance with specimens: J.G. Mead and C.W. Potter (USNM), J.E. Heyning and D. Janiger (LACM), A.E. Sanders (ChM), A. Grebneff (OU), and L. Rowe (OM). University of Wyoming undergraduate students M. Klein and P. Haselhorst provided assistance with the chemical treatment of specimens prior to analysis. We thank C. Macdonald, P. Warden, and D. Wolfe for assistance when analyzing specimens at the University of Wyoming Stable Isotope Facility. Funding was provided by grants from the National Science Foundation to MTC ( SGP EAR 0847413 ) and to DLF ( SGP EAR 0519052 ), and from the National Geographic Society to REF ( 3542–87 , 3657–87 , 4024–88 , 4314–90 , 4846–92 , 5381–94 and 6164–98 ). We thank the Geology Museum, University of Otago for permission to include the photo of OU22294 (Fig. 2). We also appreciate the helpful comments provided by two anonymous reviewers.

Keywords

Archaeoceti
Bulla
Enamel
Filter feeding
Neoceti
Oligocene
Stable isotopes

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title = "Ancient marine isoscapes and isotopic evidence of bulk-feeding by Oligocene cetaceans",

abstract = "The first appearance and evolution of the crown group Cetacea - Mysticeti (baleen whales) and Odontoceti (toothed whales and dolphins) - from archaeocete ancestors corresponds with major climatic and oceanographic changes shortly before the Eocene-Oligocene boundary (ca. 34.0Ma). These environmental changes impacted marine productivity and may have sparked the evolution of the distinct bulk-feeding strategy used by mysticete whales today. The movements and feeding habits of living cetaceans can be tracked using the isotopic composition of the structural carbonate within bioapatite of their bones and teeth, which records latitudinal gradients in marine δ13C and δ18O values. Here, we exploit this relationship to determine the past movements and feeding habits of late-surviving archaeocetes (kekenodontids) and early odontocetes and mysticetes sampled from Oligocene fossil sites in the USA (latitude: ~30°N) and New Zealand (latitude: ~50°S). Bioapatite δ13C and δ18O values for fossilized tooth enamel and bullae from fossil cetaceans were surprisingly similar to those for living cetaceans, which indicates that the feeding habits of these species and the isotopic composition of Oligocene seawater (ca. 28Ma) were very close to present-day conditions. Values for toothed mysticetes and odontocetes match expectations based on cetacean species feeding at these latitudes today, suggesting these individuals were residents that foraged in close proximity to where their fossils were discovered. In contrast, the extremely low δ13C and δ18O values for some edentulous mysticetes from New Zealand are more similar to values observed in extant mysticetes that seasonally migrate to high latitudes, where they bulk-feed on lipid-rich zooplankton. Enamel δ13C values for kekenodontids showed the greatest range and overlapped with both edentulous mysticetes and resident species; these differences correlate most strongly with tooth type and may reflect an ontogenetic shift in diet associated with the transition from nursing to marine prey. When combined with evidence of increasing morphological disparity, fossil bioapatite δ13C and δ18O values support interpretations that the Oligocene was an interval of heightened taxonomic and ecological diversification within Cetacea.",

keywords = "Archaeoceti, Bulla, Enamel, Filter feeding, Neoceti, Oligocene, Stable isotopes",

author = "Clementz, {Mark T.} and Fordyce, {R. Ewan} and Peek, {Stephanie L.} and Fox, {David L.}",

note = "Funding Information: We thank the following curators and collection managers who provided us access to and assistance with specimens: J.G. Mead and C.W. Potter (USNM), J.E. Heyning and D. Janiger (LACM), A.E. Sanders (ChM), A. Grebneff (OU), and L. Rowe (OM). University of Wyoming undergraduate students M. Klein and P. Haselhorst provided assistance with the chemical treatment of specimens prior to analysis. We thank C. Macdonald, P. Warden, and D. Wolfe for assistance when analyzing specimens at the University of Wyoming Stable Isotope Facility. Funding was provided by grants from the National Science Foundation to MTC ( SGP EAR 0847413 ) and to DLF ( SGP EAR 0519052 ), and from the National Geographic Society to REF ( 3542–87 , 3657–87 , 4024–88 , 4314–90 , 4846–92 , 5381–94 and 6164–98 ). We thank the Geology Museum, University of Otago for permission to include the photo of OU22294 (Fig. 2). We also appreciate the helpful comments provided by two anonymous reviewers.",

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N1 - Funding Information: We thank the following curators and collection managers who provided us access to and assistance with specimens: J.G. Mead and C.W. Potter (USNM), J.E. Heyning and D. Janiger (LACM), A.E. Sanders (ChM), A. Grebneff (OU), and L. Rowe (OM). University of Wyoming undergraduate students M. Klein and P. Haselhorst provided assistance with the chemical treatment of specimens prior to analysis. We thank C. Macdonald, P. Warden, and D. Wolfe for assistance when analyzing specimens at the University of Wyoming Stable Isotope Facility. Funding was provided by grants from the National Science Foundation to MTC ( SGP EAR 0847413 ) and to DLF ( SGP EAR 0519052 ), and from the National Geographic Society to REF ( 3542–87 , 3657–87 , 4024–88 , 4314–90 , 4846–92 , 5381–94 and 6164–98 ). We thank the Geology Museum, University of Otago for permission to include the photo of OU22294 (Fig. 2). We also appreciate the helpful comments provided by two anonymous reviewers.

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N2 - The first appearance and evolution of the crown group Cetacea - Mysticeti (baleen whales) and Odontoceti (toothed whales and dolphins) - from archaeocete ancestors corresponds with major climatic and oceanographic changes shortly before the Eocene-Oligocene boundary (ca. 34.0Ma). These environmental changes impacted marine productivity and may have sparked the evolution of the distinct bulk-feeding strategy used by mysticete whales today. The movements and feeding habits of living cetaceans can be tracked using the isotopic composition of the structural carbonate within bioapatite of their bones and teeth, which records latitudinal gradients in marine δ13C and δ18O values. Here, we exploit this relationship to determine the past movements and feeding habits of late-surviving archaeocetes (kekenodontids) and early odontocetes and mysticetes sampled from Oligocene fossil sites in the USA (latitude: ~30°N) and New Zealand (latitude: ~50°S). Bioapatite δ13C and δ18O values for fossilized tooth enamel and bullae from fossil cetaceans were surprisingly similar to those for living cetaceans, which indicates that the feeding habits of these species and the isotopic composition of Oligocene seawater (ca. 28Ma) were very close to present-day conditions. Values for toothed mysticetes and odontocetes match expectations based on cetacean species feeding at these latitudes today, suggesting these individuals were residents that foraged in close proximity to where their fossils were discovered. In contrast, the extremely low δ13C and δ18O values for some edentulous mysticetes from New Zealand are more similar to values observed in extant mysticetes that seasonally migrate to high latitudes, where they bulk-feed on lipid-rich zooplankton. Enamel δ13C values for kekenodontids showed the greatest range and overlapped with both edentulous mysticetes and resident species; these differences correlate most strongly with tooth type and may reflect an ontogenetic shift in diet associated with the transition from nursing to marine prey. When combined with evidence of increasing morphological disparity, fossil bioapatite δ13C and δ18O values support interpretations that the Oligocene was an interval of heightened taxonomic and ecological diversification within Cetacea.

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KW - Stable isotopes

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ER -

Ancient marine isoscapes and isotopic evidence of bulk-feeding by Oligocene cetaceans

Abstract

Bibliographical note

Keywords

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