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首页> 外文期刊>Zoological Journal of the Linnean Society >Reassessment of the Lower Cretaceous (Barremian) pliosauroid Leptocleidus superstes Andrews, 1922 and other plesiosaur remains from the nonmarine Wealden succession of southern England
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Reassessment of the Lower Cretaceous (Barremian) pliosauroid Leptocleidus superstes Andrews, 1922 and other plesiosaur remains from the nonmarine Wealden succession of southern England

机译：对下白垩纪（巴雷米亚）蛇颈龙类鳞翅目的重新评估取代了安德鲁斯（Andrews），1922年以及英格兰南部非海洋Wealden继承的其他蛇颈龙遗骸

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摘要

The Lower Cretaceous (upper Berriasian to lowermost Aptian) nonmarine Wealden succession of southern England has been a prolific source of vertebrate fossils for over 180 years. The sequence is most famous for terrestrial reptiles, particularly dinosaurs; however, significant aquatic tetrapod discoveries including rare nonmarine plesiosaurs have also been reported. The record of Wealden plesiosaurs currently incorporates a single valid taxon, Leptocleidus superstes Andrews, 1922a, based on a partial skeleton and skull from the Barremian Upper Weald Clay Formation of Berwick, Sussex. Traditional classifications place this plesiomorphic pliosauroid with basal Jurassic rhomaleosaurids; however, the genus Leptocleidus has since become a 'waste basket' for various Cretaceous rhomaleosaurid-like plesiosaurs from around the globe. In an attempt to clarify this situation, the type specimen of L. superstes was reexamined and redescribed. Previously unrecorded anatomical features were identified including an elongate, gracile paraoccipital process on the exoccipital-opisthotic, and tooth ornament comprising widely spaced, coarse striations that are restricted to the lingual surface of the crown (mesiodistal 'carinae' are absent). Other indeterminate pliosauroid remains (recovered along with coeval elasmosaurids) from the upper Berriasian-Valanginian Hastings Beds Group also exhibit potentially diagnostic traits: an atlas centrum with no anterolateral exposure and with ventral margin formed by the intercentrum; a single-headed rib articulation on the atlas centrum extending onto the axis centrum; and epipodials that are longer than broad. The placement of L. superstes is controversial in recent phylogenies. To test the competing hypotheses, L. superstes together with all closely related species were rescored into the most comprehensive published phylogenetic data sets of Plesiosauria and Pliosauroidea. Separate maximum parsimony and Bayesian analyses of each matrix unanimously supported a relationship between L. superstes and pliosauroids but could not confirm placement within either Rhomaleosauridae sensu stricto, or a discrete 'leptocleidoid' clade. Examination of character states advocating affinities amongst Leptocleidus spp. suggests homoplasy rather than clear homology between what are potentially palaeobiogeographically disparate genus-level taxa
机译：英格兰南部的下白垩统（贝里亚斯山脉的上部至阿普提亚山脉的下部）非海洋Wealden演替在180多年来一直是脊椎动物化石的丰富来源。该序列以陆生爬行动物（尤其是恐龙）最为著名。然而，也已经报告了重要的水生四足动物发现，包括稀有的非海洋蛇颈龙。 Wealden蛇颈龙的记录目前包含一个有效的分类群，细齿龙取代了Andrews，1922a，其基础是苏塞克斯郡Berwick的Barremian Upper Weald粘土地层的部分骨架和头骨。传统分类法将这种类同形蛇颈龙与基底侏罗纪龙脉龙一起放置。然而，钩端螺旋体属自此成为全球各种白垩纪类龙骨龙的蛇颈龙的“废物篮”。为了澄清这种情况，重新检查并描述了取代乳杆菌的类型标本。以前未记录的解剖学特征被确定，包括在枕外-骨科上长而柔韧的枕旁突突，以及包括宽间隔的，粗大的条纹的牙齿装饰物，这些条纹仅限于冠的舌表面（近中距的“隆突”不存在）。来自上层Berriasian-Valanginian Hastings Beds组的其他不确定的翼龙类残留物（与同年龄的elasmosaurids一起被发现）也表现出潜在的诊断特征：没有前外侧暴露且中心间形成腹缘的寰椎中心;阿特拉斯中心点上的单头肋骨关节延伸到轴中心点;和比宽长的附睾。在最近的系统发育中，L.superstes的位置是有争议的。为了检验相互竞争的假设，L。取代物与所有密切相关的物种一起被重新列入了最综合的翼龙和翼龙的系统发育数据集。每个矩阵的单独最大简约性和贝叶斯分析一致地支持了猪短螺旋体和类脊突类动物之间的关系，但不能确定其在Rhomaleosauridae sensu stricto或离散的“类鳞状类”进化枝中的位置。提倡钩端螺旋体之间具有亲和力的性格状态的检查。提示同质异质性，而不是潜在的古生物学地理上不同属级分类群之间的清晰同源性

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