**世界蛇龙属**（学名：*Jormungandr*）是发现于美国北达科他州坎帕期皮埃尔页岩（英语：）地层的一类已灭绝的沧龙。该属只包含一个物种，即模式种**瓦尔哈拉世界蛇龙**（***J.walhallaensis***），基于几乎完整的头骨和部分骨骼进行描述。世界蛇龙属是一类中等大小的沧龙，长约6-8米（20-26英尺），其骨骼解剖结构显示出基底沧龙类和衍生沧龙类的混合特征。

发现与命名
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学名瓦尔哈拉世界蛇龙的灵感来自北欧神话中的耶梦加得（左）和瓦尔哈拉（右）
2015年，黛博拉·谢泼德（Deborah Shepherd）在重新考察北达科他州沃尔哈拉（英语：）附近的一个公共化石挖掘点时，首次发现了正模标本。化石来自皮埃尔页岩Pembina段的膨润土层，铀铅测年法测定年代约为80.04±0.11百万年前。谢泼德向公园管理员通报了这块骨头的情况，北达科他州地质调查局高级古生物学家克林特·博伊德（Clint Boyd）也接到了通知。博伊德随后带领志愿者对该遗址进行了数年挖掘，直到2018年挖掘出了该标本的剩余部分：一个几乎完全分离的头骨，只缺失了脑壳、顶骨、眼骨和鼻子的一部分；七节颈椎、五节背椎、十一根肋骨和其他未经清修（英语：）的颅后骨骼。该标本被博伊德戏称为"Jorgie"，以NDGS 10838的编号被收藏在北达科他州遗产中心（英语：）。

随后的一项研究由美国自然历史博物馆的博士生阿米莉亚·齐特洛（Amelia Zietlow）领导，博伊德和西弗吉尼亚州古生物学家内森·范弗兰肯（Nathan Van Vranken）是合著者。研究小组最初怀疑该标本是已知最古老的沧龙属，但进一步的研究发现了沧龙属和更原始的硬椎龙属之间有一个新的中间属种的特征。 这项发表于2023年的研究将该物种命名为瓦尔哈拉世界蛇龙（*Jormungandr walhallaensis*）。种加名"walhallaensis"指的是位于北达科他州的发现地沃尔哈拉，该城市以北欧神话中的瓦尔哈拉命名。这启发了属名*Jormungandr*，这是耶梦加得的拉丁化名称，北欧神话中它环绕着世界海洋。

描述
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世界蛇龙属与人类的体型对比
世界蛇龙属是一类大型沧龙。头骨总长 72 厘米（28 英寸），下颌长 80.8 厘米（31.8 英寸）。根据这些测量结果，齐特洛及其同事估计世界蛇龙属全长为5.4-7.3米（18-24英尺）。

世界蛇龙属的化石材料拥有在基底和衍生的沧龙类中都可以看到的特征；它与更基础的硬椎龙属一样有很多牙齿，还有衍生的沧龙属所拥有的方骨结构。

第四节背椎的痕迹可能代表在死亡前或死亡后一段时间的一次咬伤事件中形成的咬痕，因为它们没有愈合的迹象。世界蛇龙属的描述者认为，这些所谓的咬痕与沧龙属的咬痕一致，但与鲨鱼的咬痕不一致，而且追踪者可能吃掉了骨骼的后半部份，导致剩余的身体部位与骨骼从身体上分离。

分类
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与世界蛇龙属密切相关的原蟒硬椎龙的头骨插图
在他们的系统发育分析中，齐特洛、博伊德和范弗兰肯（2023）将世界蛇龙属归类为沧龙科下的沧龙亚科成员，而硬椎龙属始终是其近亲。以下支序图代表了严格一致的简约分析的系统发育结果，使用几类现存的蛇蜥亚目作为外类群，仅记录了沧龙亚科支序。拓扑A记录自从86个最简约的未加权演化树，而拓扑B记录自5个具有隐含加权的演化树（k=12）。[2] 沧龙亚科的定义遵循马兹达（Madzia）和Cau在2017年提出的定义。

拓扑A：未加权的通过最大简约法得到的树状图| 

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| 沧龙亚科 Mosasaurinae | 

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| --- | --- |
|   | 特纳利达拉斯龙 *Dallasaurus turneri* |
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| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
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|   | *Clidastes 'liodontus'* |
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|   | 摩尔维尔"硬椎龙" *Clidastes 'moorevillensis'* |
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|   | 原蟒硬椎龙 *Clidastes propython* |
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|   | **瓦尔哈拉世界蛇龙** ***Jormungandr walhallaensis*** |
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|   | 史塔曼死颌龙 *Gnathomortis stadtmani* |
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|   | 克氏"倾齿龙" '*Prognathodon' kianda* |
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|   | 阿拉巴马球齿龙 *Globidens alabamaensis* |
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|   | 达科塔球齿龙 *Globidens dakotensis* |
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|   | 奥弗顿"倾齿龙" '*Prognathodon' overtoni* |
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|   | 粗齿近瘤龙 *Plesiotylosaurus crassidens* |
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|   | 怀帕拉"倾齿龙" '*Prognathodon' waiparaensis* |
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|   | 异齿沙漠龙 *Eremiasaurus heterodontus* |
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|   | 本尼森浮龙 *Plotosaurus bennisoni* |
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|   | 密苏里沧龙 *Mosasaurus missouriensis* |
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|   | 锥齿沧龙 *Mosasaurus conodon* |
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|   | 霍夫曼沧龙 *Mosasaurus hoffmannii* |
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|   | 残暴倾齿龙 *Prognathodon rapax* |
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|   | 舒尔曼"球齿龙" '*Globidens' schurmanni* |
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|   | 索尔维倾齿龙 *Prognathodon solvayi* |
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|   | 库里倾齿龙 *Prognathodon currii* |
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|   | 饱和倾齿龙 *Prognathodon saturator* |
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拓扑B: 具有隐含加权的通过最大简约法得到的树状图| 

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| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 沧龙亚科 Mosasaurinae | 

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| --- | --- |
|   | *Pluridens serpentis* |
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|   | 特纳利达拉斯龙 *Dallasaurus turneri* |
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|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
|   | 

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| --- | --- |
|   | 史塔曼死颌龙 *Gnathomortis stadtmani* |
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| --- | --- |
|   | **瓦尔哈拉世界蛇龙** ***Jormungandr walhallaensis*** |
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| --- | --- |
|   | *Clidastes 'liodontus'* |
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|   | 摩尔维尔"硬椎龙" *Clidastes 'moorevillensis'* |
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|   | 原蟒硬椎龙 *Clidastes propython* |
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| --- | --- |
|   | 克氏"倾齿龙" '*Prognathodon' kianda* |
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| --- | --- |
|   | 阿拉巴马球齿龙 *Globidens alabamaensis* |
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|   | 达科塔球齿龙 *Globidens dakotensis* |
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| --- | --- |
|   | 奥弗顿"倾齿龙" '*Prognathodon' overtoni* |
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| --- | --- |
|   | 粗齿近瘤龙 *Plesiotylosaurus crassidens* |
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|   | 怀帕拉"倾齿龙" '*Prognathodon' waiparaensis* |
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| --- | --- |
|   | 异齿沙漠龙 *Eremiasaurus heterodontus* |
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| --- | --- |
|   | 本尼森浮龙 *Plotosaurus bennisoni* |
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| --- | --- |
|   | 密苏里沧龙 *Mosasaurus missouriensis* |
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| --- | --- |
|   | 锥齿沧龙 *Mosasaurus conodon* |
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|   | 霍夫曼沧龙 *Mosasaurus hoffmannii* |
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|   | 残暴倾齿龙 *Prognathodon rapax* |
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| --- | --- |
|   | 舒尔曼"球齿龙" '*Globidens' schurmanni* |
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| --- | --- |
|   | 索尔维倾齿龙 *Prognathodon solvayi* |
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| --- | --- |
|   | 库里倾齿龙 *Prognathodon currii* |
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|   | 饱和倾齿龙 *Prognathodon saturator* |
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古环境学
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发现于皮埃尔页岩的彭比纳段的各种动物的复原图。从左上角顺时针顺序依次为：神河龙属、鱼鸟属、剑射鱼属和 原盖龟属
世界蛇龙属是在北达科他州的皮埃尔页岩（彭比纳段）的地层中发现的，其历史可以追溯到白垩纪晚期的早坎帕期，大约有8004万年的历史。这里还发现了许多其他动物化石，它们很可能与世界蛇龙属处于同一时代。这其中包括许多其他沧龙类，如硬椎龙属，宽板踝龙属（英语：），板踝龙属，扁掌龙属和海王龙属，以及鸟类（布氏鸟属，黄昏鸟属和鱼鸟属）、蛇颈龙（长喙龙属，薄板龙属， 神河龙属和三尖股龙属）、海龟（原盖龟属和弓海龟属（英语：））和几种硬骨鱼类和软骨鱼类。

参考资料
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1. 1 2 3  Timmons, J.. Ars Technica. 2023-10-23. （原始内容存档于2023-10-30）.
2. 1 2 3 4 5 6 7  Zietlow, A.R.; Boyd, C.A.; Van Vranken, N.E.. Bulletin of the American Museum of Natural History. 2023, (464)  [2023-10-30]. ISSN 0003-0090. doi:10.5531/sd.sp.60. hdl:2246/7332. （原始内容存档于2023-10-30） （美国英语）.
3. ↑  Mayorquin, Orlando.. The New York Times. 2023-11-05.
4. ↑   (新闻稿). American Museum of Natural History. 2023-10-30.
5. ↑  Madzia, D.; Cau, A.. PeerJ. 2017, **5**: e3782. ISSN 2167-8359. PMC 5602675 可免费查阅. PMID 28929018. doi:10.7717/peerj.3782 可免费查阅 （英语）.
6. ↑  Nicholls, Elizabeth L.. University of Calgary. 1988. ISBN 978-0-315-61682-0.
7. ↑  Aotsuka, Keiichi; Sato, Tamaki.. Cretaceous Research. 2016-08-01, **63**: 154–169. ISSN 0195-6671. doi:10.1016/j.cretres.2016.03.003.