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

最南端托雷斯德尔潘恩国家公园的白垩纪早期鱼龙

• 批准号: 43681091
• 负责人: Professor Dr. Wolfgang Stinnesbeck
• 金额: --
• 依托单位: Institut für Geowissenschaften
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2007
• 资助国家: 德国
• 起止时间: 2006-12-31 至 2013-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/43681091?language=en
• 关键词: Ichthyosaurs; early; Cretaceous; age; Torres

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.

在智利托雷斯德尔潘恩国家公园发现的扁翅鱼龙代表了全世界最南端、地层上最年轻和最完整的标本。经过 2009 年和 2010 年在廷德尔冰川进行的两次实地考察，总共有 39 具有关节的和半完整的骨骼，包括成体和幼体，分别属于四个不同的物种。鱼龙与菊石、箭石、双壳类双壳类和硬骨鱼以及大量植物残余物有关。鱼龙的大量集中在智利和南美洲是独一无二的，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储存库之一。廷德尔冰川的鱼龙种群可能受益于寒冷的上升流，这些上升流在陆架边缘产生了丰富的生命，包括大量的箭石和小鱼，这是鱼龙的首选食物。廷德尔地区大量近乎完整的有关节的鱼龙骨骼表明，这些动物是由于沿着海底峡谷流下的湍急泥流而造成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。它们的尸体最终处于深渊缺氧环境中，并迅速被细小的沉积物覆盖，这解释了它们为何能够保存完好。在我们上次对廷德尔冰川进行探险时，公园护林员告诉我们，在格雷冰川边缘的无冰区域（位于廷德尔地区东北约 47 公里处）发现了鱼龙骨骼的新发现。在为期四天的格雷之旅中（2010 年 3 月 8 日至 12 日），我们的博士生朱迪思·帕尔多 (Judith Pardo) 和一名公园管理员在与廷德尔地区相似且可能是同时代的沉积物中发现了另外 6 个人，全部是婴儿和青少年。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，并将灰鱼龙和相关的化石组合与廷德尔地区进行比较，那里的大多数个体都是成年的，根据我们的初步分析，该地区可能处于更远的位置，因此测深位置更深。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确定上述由浊积岩沉积引起的大规模死亡事件的反复情景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。