Probing the Ecology and Climate of the Eocene Southern Ocean With Sand Tiger Sharks Striatolamia macrota

• Main Authors: Kim, Sora L., Zeichner, Sarah S., Colman, Albert S., Scher, Howie D., Kriwet, Jürgen, Mörs, Thomas, Huber, Matthew
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: American Geophysical Union 2020
• Subjects: paleoclimate; oxygen isotope analysis; Seymour Island; paleobiology; temperature; neodymium isotope analysis; Southern Ocean; Drake Passage; Pacific; Seymour
• Online Access: https://doi.org/10.1029/2020pa003997

Many explanations for Eocene climate change focus on the Southern Ocean—where tectonics influenced oceanic gateways, ocean circulation reduced heat transport, and greenhouse gas declines prompted glaciation. To date, few studies focus on marine vertebrates at high latitudes to discern paleoecological and paleoenvironmental impacts of this climate transition. The Tertiary Eocene La Meseta (TELM) Formation has a rich fossil assemblage to characterize these impacts; Striatolamia macrota, an extinct (†) sand tiger shark, is abundant throughout the La Meseta Formation. Body size is often tracked to characterize and integrate across multiple ecological dimensions. †S. macrota body size distributions indicate limited changes during TELMs 2–5 based on anterior tooth crown height (n = 450, mean = 19.6 ± 6.4 mm). Similarly, environmental conditions remained stable through this period based on δ¹â¸O_(PO4) values from tooth enameloid (n = 42; 21.5 ± 1.6‰), which corresponds to a mean temperature of 22.0 ± 4.0°C. Our preliminary ε_(Nd) (n = 4) results indicate an early Drake Passage opening with Pacific inputs during TELM 2–3 (45–43 Ma) based on single unit variation with an overall radiogenic trend. Two possible hypotheses to explain these observations are (1) †S. macrota modified its migration behavior to ameliorate environmental changes related to the Drake Passage opening, or (2) the local climate change was small and gateway opening had little impact. While we cannot rule out an ecological explanation, a comparison with climate model results suggests that increased COâ‚‚ produces warm conditions that also parsimoniously explain the observations. © 2020 The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. Issue Online: 08 December 2020; Version of Record online: 08 December 2020; Accepted manuscript online: 06 November 2020; Manuscript ...