22 Working Up an Apatite: Teeth as Paleo -Ecological and -Climatological Archives

Teeth are used as archives of paleo -ecological, -climatological, and -biological information. This session welcomes presentations using teeth as archives or testing new methods; from morphology, microwear, and histology to geochemical tools.

Sunday, 19 October 2025
8:00 AM - 12:00 PM
HBGCC, 304A

Reconstructing a Macropredator-Rich Miocene Ocean Using Stable Calcium Isotopes

Paper number: 22-5
Program: Technical Sessions
Time: 9:10 AM – 9:25 AM

Authors

  • Tessa Holzmann Presenting Author
    Univ California - Santa Cruz, Dept. of Earth & Planetary Sciences, Santa Cruz, CA
  • Ana Valenzuela Torro
    Corporation for the Research and Advancement of Paleontology and Natural History of Atacama Park, Atacama
  • Stefania Gili
    Princeton University - Department of Geosciences, Princeton, NJ
  • John Higgins
    Princeton University - Department of Geosciences, Princeton, NJ
  • Paul Koch
    Univ California - Santa Cruz, Dept. of Earth & Planetary Sciences, Santa Cruz, CA

Abstract

Marine mammals have shaped ecosystems as architects of trophic structure for millions of years. Yet knowledge of their ancient ecology remains elusive, and many extant species are difficult to observe. The Miocene marine mammal community was diverse and transitional, including early baleen whales, raptorial sperm whales, large-bodied eared seals, and sirenians, many of which were adapted to warm, productive coastal ecosystems. Pliocene marine mammals were part of a now-extinct food web dominated by increasingly macropredatory marine vertebrates, forming an unprecedentedly long food chain. Some researchers suspect climate-driven shifts in primary productivity during the Pliocene epoch led to the extinction of many megafaunal marine vertebrate species and extreme migratory behavior in many survivors (i.e., large whales) due to resource scarcity. Calcium (δ44/40Ca) isotope variations in tooth enamel have the potential to reveal the trophic level of fossils millions of years older than what is currently accessible with nitrogen isotope (δ15N) analysis. This study presents new δ44/40Ca data from marine mammal, shark, and fish fossils from the Miocene-Pliocene Yorktown (U.S. East Coast) and Miocene Monterey (California) formations. The results support the emerging hypothesis of an exceptionally long Miocene and early Pliocene marine food chain. This is consistent with carbon (δ¹³C) and oxygen (δ¹⁸O) isotope evidence for early niche partitioning among these sympatric taxa, pointing to early marine mammal ecosystem specialization and resource differentiation. 

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-412238

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