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

在智利的托雷斯德尔潘恩国家公园发现的鸭嘴龙是世界上最南端、地层最年轻、最完整的鸭嘴龙标本。2009年和2010年，在廷德尔冰川进行了两次实地考察后，共有39具关节和不完整的骨骼，包括成年和幼年，被登记为属于四个不同物种。鱼龙与菊石、蓝石、双壳类和硬骨鱼类以及许多植物的残骸有关。鱼龙的巨大集中在智利和南美洲是独一无二的，这使廷德尔地区成为世界上侏罗纪-白垩纪海洋爬行动物的主要化石lagerstätten。廷德尔冰川的鱼龙种群可能受益于寒冷的上涌洋流，这些洋流在冰架边缘带来了丰富的生命，包括大量的蛭石和小鱼，这是鱼龙的首选食物。廷德尔地区大量近乎完整的鱼龙骨架表明，这些动物是海底峡谷湍流泥石流造成的大规模死亡的受害者。鱼龙要么直接被这些高能泥浆流抓住要么被泥浆流后面的吸力波拖入深渊。它们的身体最终处于深海缺氧环境中，并迅速被细小的沉积物覆盖，这解释了它们保存完好的原因。我们上次去廷德尔冰川探险时，公园护林员告诉我们，在距廷德尔地区东北约47公里的格雷冰川边缘的无冰区发现了新的鱼龙骨架。在为期四天的格雷之旅中(8)。- 2010年3月12日)，我们的博士生Judith Pardo和一名公园管理员在与Tyndall地区相似的沉积物中发现了另外六只幼鱼，都是幼鱼和幼鱼。我们建议将我们的研究扩展到这个新的、非常有希望的露头区域，并将灰色鱼龙和相关的化石组合与廷德尔地区进行比较，廷德尔地区的大多数个体都是成年的，根据我们的初步分析，廷德尔地区可能处于更远的位置，因此水深位置更深。这项比较调查将帮助我们明确该地区的环境和沉积背景条件，并使我们能够更精确地定义上述由浊积岩沉积引起的反复大规模死亡事件是如何导致托雷斯德尔潘恩地区海洋脊椎动物的良好保存和集中的。

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.