Abstract The bone histology of the Antarctic ornithopods Trinisaura santamartaensis and Morrosaurus antarcticus from the Upper Cretaceous (Campanian-Maastrichtian) is here studied. With the purpose to obtain information regarding their growth pattern, we analyse the bone histology of appendicular elements from the holotype specimens of both species. The cortical bone of the studied elements is constituted by fibro-lamellar tissue, with vascular canals mostly showing in a longitudinal and reticular arrangement, suggesting an accelerated growth. The cortical bone tissue is interrupted by lines of arrested growth (LAGs) and annuli. The study reveals that both the holotypes of Trinisaura and Morrosaurus were sexually mature subadults at the time of death (i.e. they died before reach somatic maturity). The growth pattern of these Antarctic ornithopods is similar to that reported for the related taxon Gasparinisaura, which lived in lower latitudes, as well as for the Australian ornithopods, taxa that inhabited polar latitudes during the Early Cretaceous. This contrasts with the pattern reported for more derived ornithopods (i.e. hadrosaurids) and ceratopsians from the Northern Hemisphere, whose growth dynamics vary in different latitudes. In this regard, Gondwanan ornithopods would present a preadaptation for endure in environments with great temperature changes along the year.

中文翻译：

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南极鸟足类三角龙和摩罗龙（恐龙、鸟臀目）骨骼微结构的生物学意义

摘要 这里研究了来自上白垩统（坎帕阶-马斯特里赫特阶）的南极鸟脚类动物 Trinisaura santamartaensis 和 Morrosaurus antarcticus 的骨骼组织学。为了获得有关其生长模式的信息，我们分析了来自两个物种的正模标本的附肢元素的骨组织学。所研究元素的皮质骨由纤维层状组织构成，血管管大多呈纵向和网状排列，表明其生长加速。皮质骨组织被生长停滞线 (LAG) 和环所中断。研究表明，Trinisaurus 和 Morrosaurus 的正模动物在死亡时都是性成熟的亚成体（即它们在达到体细胞成熟之前死亡）。这些南极鸟足类动物的生长模式与生活在低纬度地区的相关分类群 Gasparinisaura 以及早白垩世生活在极地纬度的澳大利亚鸟足类动物的生长模式相似。这与报告的更多来自北半球的鸟脚类动物（即鸭嘴龙科）和角龙类动物的模式形成对比，它们的生长动态在不同纬度上有所不同。在这方面，冈瓦纳鸟足类动物将呈现出在全年温度变化很大的环境中的适应能力。这与报告的更多来自北半球的鸟脚类动物（即鸭嘴龙科）和角龙类动物的模式形成对比，它们的生长动态在不同纬度上有所不同。在这方面，冈瓦纳鸟足类动物将呈现出在全年温度变化很大的环境中的适应能力。这与报告的更多来自北半球的鸟脚类动物（即鸭嘴龙科）和角龙类动物的模式形成对比，它们的生长动态在不同纬度上有所不同。在这方面，冈瓦纳鸟足类动物将呈现出在全年温度变化很大的环境中的适应能力。