The braincase anatomy of Simosaurus gaillardoti (Diapsida: Sauropterygia) revealed with X-ray micro-computed tomography.

IF 2.4 3区 生物学 Q2 MULTIDISCIPLINARY SCIENCES
PeerJ Pub Date : 2025-09-22 eCollection Date: 2025-01-01 DOI:10.7717/peerj.19932
Elisa H London, Dennis F A E Voeten, Henning Blom, Torsten M Scheyer
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引用次数: 0

Abstract

Sauropterygia is a clade of Mesozoic marine reptiles that includes the eosauropterygian Simosaurus gaillardoti Von Meyer, 1842, classically considered to be a member of Nothosauroidea. The braincase of this species has thus far only been studied in acid-prepared specimens. Acid preparation is a destructive technique prone to information loss, e.g., through the dissolution of thin braincase bones. Here, one well-preserved skull (SMNS 16363) that remains partially embedded in matrix has been visualised using X-ray micro-computed tomography, and the braincase region has been virtually extracted. This braincase provides valuable information on the general shape of the endocast, the existence and shape of epipterygoids, which were previously considered absent in the taxon, the course of cranial nerves and the bifurcation of the internal carotid arteries along an expanded and broad parabasisphenoid, the latter extending in a tapering cultriform process to the level of the external and internal narial openings. The arrangement of the semicircular canals of the inner ear confirms previously hypothesised adaptations for near-shore aquatic life in the species. The anatomical similarities of the braincases between Simosaurus gaillardoti and Nothosaurus marchicus, including a jugular foramen that is framed by the exoccipital medially and by the opisthotic laterally, support the current phylogenetic placement of the former as an early branching member of Nothosauroidea. The cranial flattening observed in nothosaurs relative to the less dorsoventrally flattened skull of Simosaurus reflects diverging feeding strategies. Most nothosaurs were fish-trap ambush predators, whereas Simosaurus gaillardoti had durophagous, as well as (opportunistic) piscivorous capacities. These results might indicate that specialised piscivorous predation using fish-trap dentition could be independently derived in nothosaurs and in pistosauroids (including plesiosaurs).

用x射线显微计算机断层扫描揭示了盖拉多西摩龙的颅脑解剖结构。
翼龙是中生代海洋爬行动物的一个分支,包括始翼龙Simosaurus gaillardoti Von Meyer, 1842年,被经典地认为是nothosauro总科的一员。迄今为止,这个物种的脑壳只在酸制备的标本中进行过研究。酸制备是一种容易造成信息丢失的破坏性技术,例如,通过溶解薄的脑壳骨。在这里,一个保存完好的头骨(SMNS 16363)仍然部分嵌入在基质中,使用x射线微计算机断层扫描可视化,并且已经虚拟提取了脑病例区域。该颅脑病例提供了有价值的信息,包括内腔的一般形状、上颌骨的存在和形状(以前认为在该分类群中不存在)、颅神经的走向和颈内动脉沿着扩张和宽阔的副斜棘骨分叉,后者以逐渐变细的培养状过程延伸到外、内肋开口的水平。内耳半规管的排列证实了该物种对近岸水生生物的适应性假设。盖拉多西莫龙和马基诺龙的脑壳在解剖学上的相似之处,包括颈静脉孔由枕外内侧和背骨外侧构成,支持了前者作为nothosauro总科早期分支成员的当前系统发育位置。相对于背腹较不平坦的Simosaurus颅骨,nothosaurus的颅骨变平反映了不同的进食策略。大多数无龙都是捕鱼陷阱的伏击者,而盖拉多蒂西莫龙既吃硬肉,也(机会主义地)吃鱼。这些结果可能表明,利用捕鱼器牙列的特殊食鱼捕食行为可以在nothosaurus和pistosarooid(包括蛇颈龙)中独立衍生。
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来源期刊
PeerJ
PeerJ MULTIDISCIPLINARY SCIENCES-
CiteScore
4.70
自引率
3.70%
发文量
1665
审稿时长
10 weeks
期刊介绍: PeerJ is an open access peer-reviewed scientific journal covering research in the biological and medical sciences. At PeerJ, authors take out a lifetime publication plan (for as little as $99) which allows them to publish articles in the journal for free, forever. PeerJ has 5 Nobel Prize Winners on the Board; they have won several industry and media awards; and they are widely recognized as being one of the most interesting recent developments in academic publishing.
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