Ichthyosaurs of early Cretaceous age in the Torres del Paine National Park, Southernmost

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The platypterygian ichthyosaurs discovered in the Torres del Paine National Park of Chile represent the southernmost, stratigraphically youngest and most complete specimens of this group worldwide. After two field campaigns at the Tyndall glacier in the years 2009 and 2010, a total of 39 articulated and subcomplete skeletons, both adults and juveniles, have been registered belonging to four different species.The ichthyosaurs are associated with ammonites, belemnites, inoceramid bivalves and teleostid fishes as well as numerous remnants of plants. The enormous concentration of ichthyosaurs is unique for Chile and South America and places the Tyndall locality among the prime fossil lagerstätten for Jurassic-Cretaceous marine reptiles in the world. The Ichthyosaur population from Tyndall Glacier may have profited from cold upwelling currents that caused abundant life at the shelf edge including masses of belemnites and small fish, the preferred diet of ichthyosaurs. The abundance of near complete articulated ichthyosaur skeletons in the Tyndall area suggests that the animals fell victim to mass mortalities caused by turbulent mudflows travelling down along submarine canyons. The ichthyosaurs were either caught directly by these high-energy mud flows or were dragged down into the abyss by the suction wave behind the mud flows. Their bodies ended up in an abyssal anoxic environment and were rapidly covered by fine sediment, which explains their excellent preservation.During our last expedition to the Tyndall glacier, park rangers informed us about new discoveries of ichthyosaur skeletons in an ice-free area along the rim of the Grey glacier, approximately 47 km northeast of the Tyndall locality. During a four days trip to Grey (8. – 12.3.2010), our phD student Judith Pardo and a park ranger located six additional individuals, all babies and juveniles, in sediment similar to the Tyndall area and probably coeval. We propose to extend our research to this new and highly promising outcrop area and compare the Grey ichthyosaurs and associated fossil assemblage with the Tyndall locality where most individuals are adults and which according to our initial analysis may have been in a more distal and thus deeper bathymetric position. This comparative investigation will help us to specify the environmental and depositional background conditions in the region and will allow us to define with more precision, how the above mentioned scenario of repeated mass mortality events caused by turbidite deposition led to the excellent preservation and concentration of marine vertebrates in the Torres del Paine region.