Programa de Pós-graduação em Zoologia (PPGZoo), Museu Nacional/Universidade Federal do Rio de Janeiro, Quinta da Boa Vista s/n, São Cristóvão, Rio de Janeiro, RJ, 20940-040, Brazil.
Laboratório de Sistemática e Tafonomia de Vertebrados Fósseis (LAPUG), Departamento de Geologia e Paleontologia, Museu Nacional/Universidade Federal do Rio de Janeiro, Quinta da Boa Vista s/n, São Cristóvão, Rio de Janeiro, RJ, 20940-040, Brazil.
Sci Rep. 2021 Nov 18;11(1):22281. doi: 10.1038/s41598-021-01312-4.
The recognition of ontogenetic edentulism in the Jurassic noasaurid Limusaurus inextricabilis shed new light on the dietary diversity within Ceratosauria, a stem lineage of non-avian theropod dinosaurs known for peculiar craniomandibular adaptations. Until now, edentulism in Ceratosauria was exclusive to adult individuals of Limusaurus. Here, an exceptionally complete skeleton of a new toothless ceratosaur, Berthasaura leopoldinae gen. et sp. nov., is described from the Cretaceous aeolian sandstones of the Bauru Basin, Southern Brazil. The specimen resembles adult individuals of Limusaurus by the absence of teeth but based on the unfused condition of several elements (e.g., skull, vertebral column) it clearly represents an ontogenetically immature individual, indicating that it might never have had teeth. The phylogenetic analysis performed here has nested Berthasaura leopoldinae as an early-divergent Noasauridae, not closely related to Limusaurus. It represents the most complete non-avian theropod from the Brazilian Cretaceous and preserves the most complete noasaurid axial series known so far. Moreover, the new taxon exhibits many novel osteological features, uncommon in non-avian theropods, and unprecedented even among South American ceratosaurs. These include not only toothless jaws but also a premaxilla with cutting occlusal edge, and a slightly downturned rostral tip. This indicate that B. leopoldinae unlikely had the same diet as other ceratosaurs, most being regarded as carnivorous. As the ontogenetically more mature specimens of Limusaurus, Berthasaura might have been herbivorous or at least omnivorous, corroborating with an early evolutionary divergence of noasaurids from the ceratosaurian bauplan by disparate feeding modes.
侏罗纪蜥脚型亚目恐龙 Limusaurus inextricabilis 的幼年缺齿现象的认识，为角鼻龙类（一种以独特的颅颌适应性为特征的非鸟兽脚类恐龙的主干谱系）的饮食多样性提供了新的线索。到目前为止，角鼻龙类中的幼年缺齿现象仅存在于 Limusaurus 的成年个体中。本文描述了来自巴西南部巴鲁盆地白垩纪风成砂岩中的一种新的无齿角鼻龙类，即 Berthasaura leopoldinae gen. et sp. nov.。该标本因无齿而与 Limusaurus 的成年个体相似，但基于一些元素（如头骨、脊柱）未融合的情况，它显然代表了一个未成熟的个体，表明它可能从未有过牙齿。这里进行的系统发育分析将 Berthasaura leopoldinae 嵌套为早期分化的蜥脚型亚目恐龙，与 Limusaurus 关系不密切。它是来自巴西白垩纪最完整的非鸟兽脚类恐龙，保存了迄今为止已知的最完整的蜥脚型亚目轴骨系列。此外，新分类群还具有许多非鸟兽脚类恐龙中罕见的、甚至在南美角鼻龙类中也未曾出现的新骨骼特征。这些特征不仅包括无齿的颌骨，还有带有切割咬合边缘的前颌骨和略微向下弯曲的吻端。这表明，B. leopoldinae 可能不像其他角鼻龙类那样具有相同的饮食方式，因为大多数角鼻龙类被认为是肉食性的。由于 Limusaurus 的幼年缺齿现象更为成熟，Berthasaura 可能是草食性的，或者至少是杂食性的，这与蜥脚型亚目恐龙通过不同的进食方式从角鼻龙类的基础形态中早期进化分化相吻合。
