Exceptional morphological and taxonomic diversity of early seals (Phocidae) from the Atacama Region, Chile

ABSTRACT

Contrasting with their current ranges in the Antarctic and subantarctic zones, the fossil record reveals that phocids (true and elephant seals) inhabited widespread subtropical regions across the Southern Hemisphere in the geologic past. At least four extinct phocid taxa have been described from Miocene and Pliocene fossiliferous levels in Chile and Peru, constituting two of the taxonomically richest phocid assemblages known. Still, some Chilean remains morphologically differ from those recovered from Peru, suggesting an unprecedented phocid diversity. We examined phocid mandibular remains from the Bahía Inglesa Formation in northern Chile. We identified the occurrence of the long-snouted seal Acrophoca longirostris, a morphologically distinguishable and undescribed form of Acrophoca, and Hadrokirus martini, an extinct phocid with a robust feeding morphology, constituting the first record of this taxon outside Peru. We also recognised four other indeterminate phocids with considerable morphological differences from contemporaneous taxa. Moreover, one of these specimens uniquely combines morphological attributes distinct from all known extant and extinct phocids, likely corresponding to a new taxon. These reports significantly increase the taxonomic and morphological diversities of fossil seals from the eastern South Pacific and emphasise the substantial transformations of phocid assemblages over geologic time.

KEYWORDS:

• Bahía Inglesa Formation
• marine mammals
• Neogene
• pinnipeds
• South America
• South Pacific Ocean

Acknowledgments

We thank K. Buldrini and D. Rubilar-Rogers for the access to the Fossil Vertebrate collection of the Museo Nacional de Historia Natural (Chile), N. D. Pyenson, C. W. Potter, J. G. Mead, K. M. Helgen, M. McGowen, J. J. Ososky, and D. J. Bohaska for access to Smithsonian collections of living and fossil pinnipeds over several years. We are also grateful to J. Velez-Juarbe for allowing the study of osteological specimens of pinnipeds at the Natural History Museum of Los Angeles County and R. Salas-Gismondi for their access to the fossil pinniped collection at the Museo de Historia Natural, Universidad Nacional Mayor de San Marcos. We thank N. D. Pyenson, J. Velez-Juarbe, J. Parham, R. Yury-Yañez, M. Cozzuol, M. Canals, C. Bravo Figueroa, D. Álvarez, and M. Chávez-Hoffmeister for providing comments and suggestions that improved preliminary versions of the manuscript. During the performance of this study, A. M. Valenzuela-Toro was funded by a Young Explorer Grant (9391-13) from the National Geographic Society Committee on Research Exploration, a CONICYT-PCHA/Magister Nacional/2013-221320410, an ANID PCHA/Becas Chile Doctoral Fellowship Grant No. 2016-72170286, a Smithsonian Institution Graduate and the Peter Buck Predoctoral Fellowships of the National Museum of Natural History, Smithsonian Institution. C. S. Gutstein was funded by Redes 190190 (PCI-ANID). Additional funding for this study came from a National Museum of Natural History (NMNH) Small Grant Award, discretionary funding from the NMNH Office of the Director, the Smithsonian Institution’s Remington Kellogg Fund, and two National Geographic Society Committee on Research Exploration grants (8903-11, 9019-11) to N. D. Pyenson (NMNH). We appreciate the detailed comments from R. W. Boessenecker, J. Rule, and an additional anonymous reviewer whose feedback improved this manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the Agencia Nacional de Investigación y Desarrollo [ANID-PCHA/Becas Chile/2016-72170286]; National Geographic Society [Young Explorer Grant (9391-13)]; National Museum of Natural History [Graduate Fellowship]; Universidad de Chile [Redes 190190 (PCI-ANID)].