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首页> 美国卫生研究院文献>other >Insight on the anatomy systematic relationships and age of the Early Cretaceous ankylopollexian dinosaur Dakotadon lakotaensis
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Insight on the anatomy systematic relationships and age of the Early Cretaceous ankylopollexian dinosaur Dakotadon lakotaensis

机译：洞察早白垩纪强脊龙恐龙Dakotadon lakotaensis的解剖系统关系和年龄

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Knowledge regarding the early evolution within the dinosaurian clade Ankylopollexia drastically increased over the past two decades, in part because of an increase in described taxa from the Early Cretaceous of North America. These advances motivated the recent completion of extensive preparation and conservation work on the holotype and only known specimen of Dakotadon lakotaensis, a basal ankylopollexian from the Lakota Formation of South Dakota. That specimen (SDSM 8656) preserves a partial skull, lower jaws, a single dorsal vertebra, and two caudal vertebrae. That new preparation work exposed several bones not included in the original description and revealed that other bones were previously misidentified. The presence of extensive deformation in areas of the skull is also noted that influenced inaccuracies in prior descriptions and reconstructions of this taxon. In addition to providing an extensive re-description of D. lakotaensis, this study reviews previously proposed diagnoses for this taxon, identifies two autapomorphies, and provides an extensive differential diagnosis. Dakotadon lakotaensis is distinct from the only other ankylopollexian taxon known from the Lakota Formation, Osmakasaurus depressus, in the presence of two prominent, anteroposteriorly oriented ridges on the ventral surfaces of the caudal vertebrae, the only overlapping material preserved between these taxa. The systematic relationships of D. lakotaensis are evaluated using both the parsimony and posterior probability optimality criteria, with both sets of analyses recovering D. lakotaensis as a non-hadrosauriform ankylopollexian that is more closely related to taxa from the Early Cretaceous (e.g., Iguanacolossus, Hippodraco, and Theiophytalia) than to more basally situated taxa from the Jurassic (e.g., Camptosaurus, Uteodon). This taxonomic work is supplemented by field work that relocated the type locality, confirming its provenance from unit L2 (lower Fuson Member equivalent) of the Lakota Formation. Those data, combined with recently revised ages for the members of the Lakota Formation based on charophyte and ostracod biostratigraphy, constrain the age of this taxon to the late Valanginian to early Barremian.
机译：在过去的二十年中，有关恐龙进化枝甲虫的早期进化的知识急剧增加，部分原因是北美早白垩世描述的类群的增加。这些进展促使最近完成了对整型和仅已知的Dakotadon lakotaensis标本的广泛准备和保存工作，Dakotadon lakotaensis是南达科他州Lakota组的基础甲极。该标本（SDSM 8656）保留了部分颅骨，下颌，单个背椎和两个尾椎。这项新的准备工作暴露了原始描述中未包括的几根骨头，并揭示了其他骨头先前被误认了。还注意到在颅骨区域中存在广泛的变形，这影响了该分类单元的先前描述和重建中的不准确性。除了提供对D. lakotaensis的广泛描述外，本研究还回顾了先前对该类群提出的诊断方法，确定了两种自交形，并提供了广泛的鉴别诊断。 Dakotadon lakotaensis有别于从Lakota组已知的唯一另一种强直性类群，Osmakasaurus depressus，在尾椎腹面有两个突出的，前后定向的脊，这是这些类群之间唯一保留的重叠材料。使用简约性和后验概率最优标准评估了D. lakotaensis的系统关系，两组分析都将D. lakotaensis回收为一种与白垩纪早期（例如Iguanacolossus， Hippodraco和Theiophytalia）要比侏罗纪的基类生物群（例如Camptosaurus，Uteodon）更靠近。这项分类学工作得到了野外工作的补充，该工作重新定位了类型局部性，从Lakota地层的L2单元（下等的Fuson构件当量）确认了其起源。这些数据，再加上最近基于风化石和真骨纲生物地层学的拉科塔组成员年龄的修订，将这一分类群的年龄限制在瓦朗吉尼晚期至巴雷米亚早期。

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