Dinocephalosaurus orientalis Li, 2003: a remarkable marine archosauromorph from the Middle Triassic of southwestern China

IF 0.9 4区 地球科学 Q4 GEOSCIENCES, MULTIDISCIPLINARY
Stephan N.F. SPIEKMAN, Wei WANG, Lijun ZHAO, Olivier RIEPPEL, Nicholas C. FRASER, Chun LI
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Abstract

The non-archosauriform archosauromorph Dinocephalosaurus orientalis was first described from the Upper Member of the Guanling Formation (late Anisian, Middle Triassic) of Guizhou Province by Li in 2003 on the basis of a complete articulated skull and the first three cervical vertebrae exposed in dorsal to right lateral view. Since then, additional specimens have been discovered in southwestern China. Here, five newly discovered specimens are described for the first time, and redescriptions of the holotype IVPP V13767 and another referred specimen, IVPP V13898, are provided. Together, these permit the description of the complete skeleton of this remarkable long-necked marine reptile. The postcranial skeleton is as much as 6 metres long, and characterised by its long tail and even longer neck. The appendicular skeleton exhibits a high degree of skeletal paedomorphosis recalling that of many sauropterygians, but the skull and neck are completely inconsistent with sauropterygian affinities. The palate does not extend back over the basisphenoid region and lacks any development of the closed condition typical of sauropterygians. The arrangement of cranial elements, including the presence of narial fossae, is very similar to that seen in another long-necked archosauromorph, Tanystropheus hydroides, which at least in part represents a convergence related to an aquatic piscivorous lifestyle. The long and low cervical vertebrae support exceptionally elongate cervical ribs that extend across multiple intervertebral joints and contribute to a ‘stiffening bundle of ribs’ extending along the entire ventral side of the neck, as in many other non-crocopodan archosauromorphs. The functional significance of the extraordinarily elongate neck is hard to discern but it presumably played a key role in feeding, and it is probably analogous to the elongate necks seen in pelagic, long-necked plesiosaurs. Dinocephalosaurus orientalis was almost certainly a fully marine reptile and even gave birth at sea.

东方恐龙李, 2003: 中国西南部中三叠世的一种杰出的海洋古龙形态
根据一个完整的头骨和从背侧到右侧暴露出的前三节颈椎,2003年,李晓东首次在贵州省关岭地层上统(晚安息世,中三叠世)描述了非弓形古龙形态的东方恐龙。此后,在中国西南部又发现了一些标本。本文首次描述了五个新发现的标本,并重新描述了主模式 IVPP V13767 和另一个参考标本 IVPP V13898。通过这些研究,我们得以描述这种非凡的长颈海洋爬行动物的完整骨骼。颅后骨骼长达 6 米,其特点是尾巴很长,脖子更长。附肢骨骼表现出高度的骨骼畸形,令人想起许多长颈龙类的骨骼畸形,但头骨和颈部与长颈龙类的亲缘关系完全不一致。上颚没有向后延伸到蝶骨基部,也没有发育出长尾椎动物典型的闭合状态。颅骨元素的排列,包括鼻骨窝的存在,与另一种长颈古龙类动物水龙(Tanystropheus hydroides)非常相似,这至少在一定程度上代表了与水生食鱼生活方式有关的趋同。长而低的颈椎支撑着特别细长的颈肋,这些颈肋横跨多个椎间关节,形成了沿着整个颈部腹侧延伸的 "肋骨加固束",这与许多其他非鳄形古龙类的情况相同。超长颈部的功能意义很难辨别,但它可能在进食中发挥了关键作用,而且它很可能类似于浮游长颈长鼻龙的长颈。东方恐龙几乎可以肯定是一种完全海洋性的爬行动物,甚至可以在海上分娩。
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来源期刊
CiteScore
2.00
自引率
0.00%
发文量
21
期刊介绍: Earth and Environmental Science Transactions (formerly Transactions of the Royal Society of Edinburgh: Earth Sciences) is a general earth sciences journal publishing a comprehensive selection of substantial peer-reviewed research papers, reviews and short communications of international standard across the broad spectrum of the Earth and its surface environments. The journal prides itself on the quality of its graphics and photographic reproduction. The Editors are keen to encourage interdisciplinary papers and Transactions also publishes occasional special symposia and invited volumes of specific interest. We are currently in the process of digitising the archive of RSE Publications, and the archive of the Transactions, dating back to 1788, will be available from the back issues link on this site.
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