南非新种恐龙 Nyana rooiwalensis 公布：幼体已重约400公斤，近乎完整的头骨来自晚三叠世
南非 University of the Witwatersrand 领衔的团队在《Royal Society Open Science》发表论文，把一种新恐龙命名为 Nyana rooiwalensis。这一物种生活在2亿多年前的南非境内，根据一块近乎完整的头骨和数块其他化石骨骼识别，属于后来演化出 Brachiosaurus 与 Diplodocus 等长颈巨兽的蜥脚形类恐龙。
化石于2018年在 Eastern Cape 的 Qhemegha 村附近采集，正模标本编号 BP/1/8468，保存的头骨长21.3厘米。研究人员用强力 X 光为头骨建立了详细的三维模型，再把其特征与其他蜥脚形类恐龙逐一比对，以确定它在恐龙家族树上的位置。
对肢骨薄片的显微观察显示，这只 Nyana 死亡时仍在快速生长，已至少进入第三个生长年。团队按股骨周长并比对近缘恐龙的生长曲线估算，它当时已重约400公斤，约880磅，很可能以双足行走。论文作者写道，按生长曲线外推，成年 Nyana 可能达到数吨体重。
这一化石来自下 Elliot 组地层，年代属晚三叠世的 Norian 至 Rhaetian 期。研究者表示，该标本是南非晚三叠世第一块近乎完整、相互关联的恐龙头骨，这类年代的蜥脚形类头骨在南部非洲尤其罕见，其系统位置分析显示它与北美的 Sarahsaurus 或南非的 Ngwevu 互为近亲，为研究早期蜥脚形类恐龙的演化与扩散提供了新数据。
New South African Dinosaur Nyana rooiwalensis: Juvenile Already Weighed About 400 Kilograms, From a Near-Complete Late Triassic Skull
A team led by Atashni Moopen of South Africa's University of the Witwatersrand has described a new dinosaur, Nyana rooiwalensis, in Royal Society Open Science (DOI: 10.1098/rsos.261002). The animal lived more than 200 million years ago in what is now South Africa and was identified from a near-complete skull and several other fossilized bones. It belonged to the sauropodomorphs, the group that eventually gave rise to long-necked giants such as Brachiosaurus and Diplodocus.
The fossil was collected in 2018 near Qhemegha village in the Eastern Cape, and the holotype, specimen BP/1/8468, preserves a skull measuring 21.3 centimeters. The researchers used powerful X-rays to create a detailed 3D model of the skull and compared its features with those of other sauropodomorphs to place Nyana on the dinosaur family tree.
Thin slices of limb bones examined under a microscope showed the animal was still growing rapidly when it died, and was at least in its third year of growth. By measuring the circumference of its thigh bone and comparing it with growth curves from related dinosaurs, the team estimated it already weighed about 400 kilograms, or 880 pounds, and probably walked on two legs. Extrapolation of the growth curves suggests adults may have reached multi-tonne body masses, the authors wrote.
The remains come from the lower Elliot Formation, of Norian to Rhaetian age in the Late Triassic. The specimen is the first almost complete, articulated dinosaur skull from the South African Late Triassic, and fossilized skulls of sauropodomorphs of this age are relatively rare in southern Africa. Analyses recover Nyana as a close relative of Sarahsaurus from North America or of the South African Ngwevu, providing new data on how these early dinosaurs evolved and spread.
来源：《皇家学会开放科学》
发布：GSM·美国（发布链接）
图片来源：图：新种恐龙 Nyana rooiwalensis 的正模头骨化石（标本 BP/1/8468）的三个视图。来源：A. Moopen 等，《皇家学会开放科学》，CC BY 4.0。 / Photo: Three views of the holotype skull fossil of the new dinosaur Nyana rooiwalensis (specimen BP/1/8468). Source: A. Moopen et al., Royal Society Open Science, CC BY 4.0.
GSM Global · 本篇英文版 English edition of this story
