Gigantic mysticete predators roamed the Eocene Southern Ocean

Modern baleen whales (Mysticeti), the largest animals on Earth, arose from small ancestors around 36.4 million years ago (Ma). True gigantism is thought to have arisen late in mysticete history, with species exceeding 10 m unknown prior to 8 Ma. This view is challenged by new fossils from Seymour Island (Isla Marambio), Antarctica, which suggest that enormous whales once roamed the Southern Ocean during the Late Eocene (c. 34 Ma). The new material hints at an unknown species of the archaic mysticete Llanocetus with a total body length of up to 12 m. The latter is comparable to that of extant Omura's whales (Balaenoptera omurai Wada et al. 2003), and suggests that gigantism has been a re-occurring feature of mysticetes since their very origin. Functional analysis including sharpness and dental wear implies an at least partly raptorial feeding strategy, starkly contrasting with the filtering habit of living whales. The new material markedly expands the size range of archaic mysticetes, and demonstrates that whales achieved considerable disparity shortly after their origin.This is the peer-reviewed version of the following article: Marx, F.G., Buono, M.R., Evans, A.R., Fordyce, R.E., Reguero, M., and Hocking, D.P. (2019). Gigantic mysticete predators roamed the Eocene Southern Ocean. Antarctic Science 31, 98-104, which has been published in final form at https://www.cambridge.org/core/journals/antarctic-science/article/gigantic-mysticete-predators-roamed-the-eocene-southern-ocean/0EEFC32753A8909BC4E7C134F5AEA6AE. This version is free to view and download for private research and study only. Not for re-distribution, re-sale or use in derivative works. © Antarctic Science Ltd 2019