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| Figure 1. Geographical and stratigraphical provenance of the remains described here. Figure 2. View of the north-west side of the Seymour Island. The arrow indicates the position of locality IAA 1/13. |
Abstract
New fossil mammals found at the base of Acantilados II Allomember of the La Meseta Formation, from the early Eocene (Ypresian) of Seymour Island, represent the oldest evidence of this group in Antarctica. Two specimens are here described; the first belongs to a talonid portion of a lower right molar assigned to the sparnotheriodontid litoptern Notiolofos sp. cf. N. arquinotiensis. Sparnotheriodontid were medium- to large-sized ungulates, with a wide distribution in the Eocene of South America and Antarctica. The second specimen is an intermediate phalanx referred to an indeterminate Eutheria, probably a South American native ungulate. These Antarctic findings in sediments of 55.3 Ma query the minimum age needed for terrestrial mammals to spread from South America to Antarctica, which should have occurred before the final break-up of Gondwana. This event involves the disappearance of the land bridge formed by the Weddellian Isthmus, which connected West Antarctica and southern South America from the Late Cretaceous until sometime in the earliest Palaeogene.
Keywords: West Antarctica; Palaeogene; Ypresian; tooth and bone morphology; ungulates; Sparnotheriodontidae
Class MAMMALIA Linnaeus, 1758
Order LITOPTERNA Ameghino, 1889
Family SPARNOTHERIODONTIDAE Soria, 1980
Genus NOTIOLOFOS Bond, Reguero, Vizcaíno, Marenssi and Ortiz Jaureguizar, 2009
Type species: Notiolofos arquinotiensis (Bond, Reguero, Vizcaíno and Marenssi, 2006).
Notiolofos cf. N. arquinotiensis (Bond, Reguero, Vizcaíno and Marenssi, 2006)
Javier N. Gelfo, Thomas Mörs, Malena Lorente, Guillermo M. López, Marcelo Reguero. in press. The Oldest Mammals from Antarctica, early Eocene of the La Meseta Formation, Seymour Island. Palaeontology. doi: dx.doi.org/10.1111/pala.12121.
Bond, M., Reguero, M. A., Vizcaíno, S. F. and Ortiz-Jaureguizar, E. 2009. Notiolofos, a replacement name for Notolophus Bond, Reguero, Vizcaíno and Marenssi, 2006, a preoccupied name. Journal of Vertebrate Paleontology. 29, 979.
Bond, M., Reguero, M. A., Vizcaíno, S. F. and Ortiz-Jaureguizar, E. 2009. Notiolofos, a replacement name for Notolophus Bond, Reguero, Vizcaíno and Marenssi, 2006, a preoccupied name. Journal of Vertebrate Paleontology. 29, 979.
M. Bond, M. A. Reguero, S. F. Vizcaíno and S. A. Marenssi. 2006. A New ‘South American ungulate’ (Mammalia: Litopterna) from the Eocene of the Antarctic Peninsula. In J. E. Francis, D. Pirrie, J. A. Crame (eds). Cretaceous-tertiary high-latitude palaeoenvironments: James Ross Basin, Antarctica. The Geological Society of London. 258(1): 163–176. doi: dx.doi.org/10.1144/GSL.SP.2006.258.01.12.
