New avian tracks from King George Island, Antarctica

• Main Authors: Masilla, Héctor, Leppe, Marcelo, de Valais, Silvina, Varela, Natalia
• Language: English
• Published: 2010
• Subjects: Ciencias Exactas y Naturales; Vertebrate and Invertebrate Trace Fossils; Fossil Hill Formation; Middle Eocene; King George Island; Antarctica; Argentina; Fossil Hill; Mansilla; Varela; Antarc*
• Online Access: http://rid.unrn.edu.ar/handle/20.500.12049/5952; https://hdl.handle.net/20.500.12049/5952

Fil: Mansilla, Héctor. Instituto Antártico Chileno. Laboratorio de Palaeobiología; Chile. Fil: Leppe, Marcelo. Instituto Antártico Chileno. Laboratorio de Palaeobiología; Chile. Fil: de Valais, Silvina. Universidad Nacional de Rio Negro. Instituto de Investigaciones en Paleobiologia y Geologia. Río Negro, Argentina. Fil: Varela, Natalia. Earth Sciences Department, University of Concepción; Chile. Trace fossils are known to exist in the type locality of the Fossil Hill Formation (Middle Eocene) at Fossil Hill, King George Island, Antarctica, since at least four decades. However, during fieldwork in 2009, abundant new avian tracks and invertebrate traces have been recovered, which are analyzed here. Three avian ichnotaxa are distinguished in this study. The most common tracks are tridactyl or tetradactyl, with the slender digit II to IV imprints anteriorly directed and a posterior hallux impression, and are included in Gruipeda. The rest of the footprints have tentatively been assigned to Presbyoniformipes which includes four wide, short digit impressions with present of webbing mark, and to Avipeda, composed of a tetradactyl track with a prominent claw; both being documented in the locality for the first time. The invertebrate traces include simple structures, such as Helminthoidichnites and Skolithos, and at least an undetermined arthropod trace, composed of a slightly sinusoidal trail, characterized by oblique and parallel to irregular marks. Both invertebrate and avian traces are preserved in a volcaniclastistic sediment sequence intercalated with fine grained agglomerates. They support a lacustrine environment which seasonally dried and was episodically refilled. The trace fossil assemblage from Fossil Hill displays a typical Scoyenia ichnofacies setting, particularly of a shorebird ichnofacies. Further detailed studies of this site will be useful to the recognition of subdivisions of the Scoyenia ichnofacies and will allow us to reconstruct the paleocommunity and paleoenviroment during the Eocene in ...