Data from: Probing the ecology and climate of the Eocene Southern Ocean with sand tiger sharks Striatolamia macrota

During the Eocene, the Earth climate system transitioned from greenhouse
to icehouse conditions. Central to many explanations is the Southern
Ocean—where tectonic configurations influenced oceanic gateways, ocean
circulation reduced heat transport, and/or greenhouse gas declines
prompted glaciation. To date, few studies have explored the implications
of this climate transition on high latitude, marine vertebrates. Seymour
Island near the Antarctic Peninsula preserves a rich, diverse fossil
assemblage in the Tertiary Eocene La Meseta (TELM) Formation (Fm). We
examine teeth of Striatolamia macrota, an extinct (†) sand tiger shark
that is abundant throughout the La Meseta Fm. to discern ecological and
environmental characteristics. Body size is an integrative ecological
trait often tracked through time and space. †Striatolamia macrota body
size distributions indicate no shifts during TELMs 2-5 based on anterior
tooth crown height (n=450, mean=19.6 ± 6.4 mm, total body length 88-389
cm). Similarly, environmental conditions seem to remain stable through
this period based on †S. macrota enameloid with mean d18OPO4 value of 21.5
± 1.6‰ (n=39) and mean temperature estimates of 22.2 ± 5.4°C. This
ecological and environmental stasis is intriguing given changes in ocean
circulation as tracked by neodymium isotope composition. Our preliminary
eNd (n=4) results indicate an early Drake Passage opening with Pacific
inputs as early as TELM 2 based on 1 unit variation with an overall
radiogenic trend, similar to previous results from deep ocean localities.
We hypothesize that †S. macrota modified its migration behavior to
preclude environmental changes related to the Drake Passage opening. Our
results shed important light on paleoceanographic conditions and indicate
paleoecological responses to climate change.