Early monk seals (Monachinae: Monachini) from the late Miocene–early Pliocene of Australia

Abstract

Despite decades of research, the systematics of extinct true seals (Phocidae) is still overly reliant on morphological data from extant taxa. As a result, monk seals (Monachini) have been interpreted as ‘archaic’ despite an absence of fossil data to support this hypothesis. This has affected systematic hypotheses for extinct phocids, including fossils from Australasia. Recent finds from New Zealand indicate that the first seal fossils described from Australia, two temporal bones from the late Miocene–early Pliocene (6.24–4.35 Ma), need to be revisited. Here we re-describe these temporal bones and find them to represent monk seals. This places the oldest known fossils of this group in the Southern Hemisphere, implying monk seals had a longer history at southern latitudes. Our ancestral state estimation of the temporal bone morphology of monachines indicates that monk seal temporals may be derived, rather than plesiomorphic as has previously been assumed. This suggests that an over-reliance on the morphology of extant true seals may be obscuring the true diversity of both stem- and crown-phocids, and indicates that a rethink of the morphology underlying the taxonomic assessments of fragmentary true seal fossils is needed.

Keywords:

• monk seal
• Australia
• Neogene
• Monachinae
• seal auditory anatomy

Acknowledgements

JPR is supported by an Australian Government Research Training Program (RTP) and a Robert Blackwood Partnership PhD scholarship, in addition to a Monash Postgraduate Publication Award. Travel for this project was funded by Monash’s Biomedical Discovery Institute and Department of Anatomy and Developmental Biology, with additional funds provided by a Monash University Graduate Research Travel Grant. T. Pollock, A. R. Evans, S. Cleuren, M. Camaiti, K. Garland and D. S. Rovinsky are thanked for troubleshooting assistance with R. The following museum staff are thanked for collections access and support: A. Tennyson and T. Schultz (Museum of New Zealand Te Papa Tongarewa); R. P. Scofield and T. Elder (Canterbury Museum); E. Ruigomez (Museo Paleontológico ‘Egidio Feruglio’); T. Ziegler, K. Roberts, K. Date, R-L. Erickson, and K. Rowe (Museums Victoria); D. Stemmer (South Australian Museum); T. Park, R. Miguez and P. Jenkins (Natural History Museum, London); C. de Muizon and G. Billet (Muséum national d’Histoire naturelle); J. Mead, J. Ososky, M. McGowen, D. Lunde, D. Bohaska and N. Pyenson (Smithsonian Institution National Museum of Natural History). Thanks to the editor (T. J. D. Halliday) and the reviewers (L. Dewaele, N. Kohno and one anonymous reviewer) for constructive comments that improved the quality of the manuscript. This is a contribution to research on the Lost World of Bayside supported by Bayside City Council, Beaumaris Motor Yacht Squadron, Sandringham Community Bank Branch of Bendigo Bank, Sandringham Foreshore Association, Bayside Earth Sciences Society and many generous community members.

Supplemental material

Supplemental material for this article can be accessed here: https://doi.org/10.1080/14772019.2021.1920639.

Associate Editor: Thomas Halliday