Distributed under Creative Commons Cc-by 4.0 the Cranial Anatomy of the Neornithischian Dinosaur Thescelosaurus Neglectus
Distributed under Creative Commons Cc-by 4.0 the Cranial Anatomy of the Neornithischian Dinosaur Thescelosaurus Neglectus
复制标题
DOI：
--
复制
发表时间：
--
期刊：
影响因子：
--
通讯作者：
Clint A. Boyd
中科院分区：
文献类型：
--
作者：
Clint A. Boyd
虽然恐龙Thescelosaurus neglectus在1913年首次被描述，并在北美西部内陆盆地的相对多产的兰斯和地狱溪地层中被发现，但该物种的颅骨解剖仍然知之甚少。唯一有把握地提到这个物种的头盖骨材料是与副模式一起保存的三块碎片骨骼，阻碍了试图了解这个分类群在新鸟臀目内的系统关系。这里是T.基于两个标本，包括保存完好的颅骨材料（NCSM 15728和TLAM.BA.2014.027.0001），首次全面描述了疏忽症。通过NCSM 15728中的详细CT数据对这些标本暴露的颅骨元素进行目视检查，从而能够检查其他未暴露的表面，有助于完整描述该物种的颅骨解剖结构。T. neglectus显示出独特的近形和近形性状的组合。前上颌骨和“颊”齿的形态是相对衍生的，虽然比基禽龙的情况少，这表明在前上颌骨，上颌骨和牙齿中存在的高齿数可能与该物种头骨的极端伸长有关，而不是保留了近形条件。头骨的形态与禽龙科的鳞龙和异蜥龙最为相似，特别是在前耳的形态上。其中一个自形特征是第一次被确认，沿着几个额外的头骨特征，区分这个物种与密切相关的和同时代的Thescelosaurus assiniboiensis。已发表的新鸟臀目恐龙亲缘关系的系统发育假说通常在北美分类群帕克索龙的位置上有所不同，有些与Thescelosaurus恢复了密切的关系，而另一些则与南美分类群Gasparinisaura恢复了密切的关系，但从未同时恢复。新的形态学观察，结合对帕克索龙正模标本的重新研究，表明帕克索龙与赛塞隆龙的关系比与加斯帕里尼萨龙的关系更近，并且许多先前引用的支持与后者分类单元关系的特征也存在于赛塞隆龙中，是保存的文物，或者是不完整的准备和不准确的标本解释的结果。此外，Thescelosaurus和Parksosaurus的头骨和下颚的整体形态也非常类似于亚洲分类群长春龙和Haya，尽管这些分类群的相互关系还有待于系统发育分析，包括T的这些新形态数据。…
Though the dinosaur Thescelosaurus neglectus was first described in 1913 and is known from the relatively fossiliferous Lance and Hell Creek formations in the Western Interior Basin of North America, the cranial anatomy of this species remains poorly understood. The only cranial material confidently referred to this species are three fragmentary bones preserved with the paratype, hindering attempts to understand the systematic relationships of this taxon within Neornithischia. Here the cranial anatomy of T. neglectus is fully described for the first time based on two specimens that include well-preserved cranial material (NCSM 15728 and TLAM.BA.2014.027.0001). Visual inspection of exposed cranial elements of these specimens is supplemented by detailed CT data from NCSM 15728 that enabled the examination of otherwise unexposed surfaces, facilitating a complete description of the cranial anatomy of this species. The skull of T. neglectus displays a unique combination of plesiomorphic and apomorphic traits. The premaxillary and 'cheek' tooth morphologies are relatively derived, though less so than the condition seen in basal iguanodontians, suggesting that the high tooth count present in the premaxillae, maxillae, and dentaries may be related to the extreme elongation of the skull of this species rather than a retention of the plesiomorphic condition. The morphology of the braincase most closely resembles the iguanodontians Dryosaurus and Dysalotosaurus, especially with regard to the morphology of the prootic. One autapomorphic feature is recognized for the first time, along with several additional cranial features that differentiate this species from the closely related and contemporaneous Thescelosaurus assiniboiensis. Published phylogenetic hypotheses of neornithischian dinosaur relationships often differ in the placement of the North American taxon Parksosaurus, with some recovering a close relationship with Thescelosaurus and others with the South American taxon Gasparinisaura, but never both at the same time. The new morphological observations presented herein, combined with re-examination of the holotype of Parksosaurus, suggest that Parksosaurus shares a closer relationship with Thescelosaurus than with Gasparinisaura, and that many of the features previously cited to support a relationship with the latter taxon are either also present in Thescelosaurus, are artifacts of preservation, or are the result of incomplete preparation and inaccurate interpretation of specimens. Additionally, the overall morphology of the skull and lower jaws of both Thescelosaurus and Parksosaurus also closely resemble the Asian taxa Changchunsaurus and Haya, though the interrelationships of these taxa have yet to be tested in a phylogenetic analysis that includes these new morphological data for T. …