Laboratório de Paleontologia, Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil.
Centro de Apoio à Pesquisa Paleontológica, Universidade Federal de Santa Maria, Santa Maria, Rio Grande do Sul, Brazil.
PLoS One. 2019 Sep 6;14(9):e0221387. doi: 10.1371/journal.pone.0221387. eCollection 2019.
Saturnalia tupiniquim is a sauropodomorph dinosaur from the Late Triassic (Carnian-c. 233 Ma) Santa Maria Formation of Brazil. Due to its phylogenetic position and age, it is important for studies focusing on the early evolution of both dinosaurs and sauropodomorphs. The osteology of Saturnalia has been described in a series of papers, but its cranial anatomy remains mostly unknown. Here, we describe the skull bones of one of its paratypes (only in the type-series to possess such remains) based on CT Scan data. The newly described elements allowed estimating the cranial length of Saturnalia and provide additional support for the presence of a reduced skull (i.e. two thirds of the femoral length) in this taxon, as typical of later sauropodomorphs. Skull reduction in Saturnalia could be related to an increased efficiency for predatory feeding behaviour, allowing fast movements of the head in order to secure small and elusive prey, a hypothesis also supported by data from its tooth and brain morphology. A principal co-ordinates analysis of the sauropodomorph jaw feeding apparatus shows marked shifts in morphospace occupation in different stages of the first 30 million years of their evolutionary history. One of these shifts is observed between non-plateosaurian and plateosaurian sauropodomorphs, suggesting that, despite also having an omnivorous diet, the feeding behaviour of some early Carnian sauropodomorphs, such as Saturnalia, was markedly different from that of later Triassic taxa. A second shift, between Late Triassic and Early Jurassic taxa, is congruent with a floral turnover hypothesis across the Triassic-Jurassic boundary.
图皮纳奎姆龙是一种兽脚亚目恐龙，来自巴西晚三叠世（卡尼阶-约 2.33 亿年前）的圣玛利亚组。由于其系统发育位置和年龄，它对于研究恐龙和蜥脚形亚目恐龙的早期演化非常重要。图皮纳奎姆龙的骨骼学已经在一系列论文中进行了描述，但它的头骨解剖结构仍然知之甚少。在这里，我们根据 CT 扫描数据描述了它的一个副型标本（仅在正型系列中具有此类遗骸）的头骨骨骼。新描述的骨骼元素允许估计图皮纳奎姆龙的头骨长度，并为该分类群中存在缩短的头骨（即股骨长度的三分之二）提供额外的支持，这是后期蜥脚形亚目恐龙的典型特征。图皮纳奎姆龙的头骨缩小可能与捕食性进食行为的效率提高有关，这允许头部快速移动，以捕获小而难以捉摸的猎物，这一假设也得到了其牙齿和脑形态数据的支持。蜥脚形亚目恐龙的颌部进食器官的主坐标分析显示，在它们进化历史的前 3000 万年的不同阶段，形态空间的占据发生了明显的变化。其中一个变化发生在非蜥脚类恐龙和蜥脚类恐龙之间，这表明，尽管它们也有杂食性饮食，但一些早期卡尼阶蜥脚形亚目恐龙的进食行为，如图皮纳奎姆龙，与后期三叠纪的分类群明显不同。第二个变化发生在晚三叠世和早侏罗世的分类群之间，与三叠纪-侏罗纪边界的植物更替假说一致。
