Roy M. Huffington Department of Earth Sciences, Southern Methodist University, Dallas, Texas, United States of America.
Ministry of Civic Education, Culture and Community Development, Lilongwe, Malawi.
PLoS One. 2019 Feb 13;14(2):e0211423. doi: 10.1371/journal.pone.0211423. eCollection 2019.
A braincase of the Cretaceous titanosaurian sauropod Malawisaurus dixeyi, complete except for the olfactory region, was CT scanned and a 3D rendering of the endocast and inner ear was generated. Cranial nerves appear in the same configuration as in other sauropods, including derived features that appear to characterize titanosaurians, specifically, an abducens nerve canal that passes lateral to the pituitary fossa rather than entering it. Furthermore, the hypoglossal nerve exits the skull via a single foramen, consistent with most titanosaurians, while other saurischians, including the basal titanosauriform, Giraffatitan, contain multiple rootlets. The size of the vestibular labyrinth is smaller than in Giraffatitan, but larger than in most derived titanosaurians. Similar to the condition found in Giraffatitan, the anterior semicircular canal is larger than the posterior semicircular canal. This contrasts with more derived titanosaurians that contain similarly sized anterior and posterior semicircular canals, congruent with the interpretation of Malawisaurus as a basal titanosaurian. Measurements of the humerus of Malawisaurus provide a body mass estimate of 4.7 metric tons. Comparison of body mass to radius of the semicircular canals of the vestibular labyrinth reveals that Malawisaurus fits the allometric relationship found in previous studies of extant mammals and Giraffatitan brancai. As in Giraffatitan, the anterior semicircular canal is significantly larger than is predicted by the allometric relationship suggesting greater sensitivity and slower movement of the head in the sagittal plane.
完整的马氏拉美西斯龙（Malawisaurus dixeyi）的脑颅，除嗅觉区域外，已被 CT 扫描，并生成了颅腔内部和内耳的 3D 渲染图。颅神经的排列方式与其他蜥脚类恐龙相同，包括一些似乎是泰坦巨龙类特有的衍生特征，例如，外展神经管位于垂体窝的外侧而不是进入其中。此外，舌下神经管通过单个孔离开颅骨，这与大多数泰坦巨龙类一致，而其他蜥臀目恐龙，包括基础的巨龙形类、长颈鹿巨龙，包含多个神经根。前庭迷路的大小小于长颈鹿巨龙，但大于大多数衍生的泰坦巨龙类。与在长颈鹿巨龙中发现的情况相似，前半规管大于后半规管。这与更衍生的泰坦巨龙类形成对比，后者的前半规管和后半规管大小相似，与将马氏拉美西斯龙解释为基础的泰坦巨龙类一致。马氏拉美西斯龙的肱骨测量值提供了一个 4.7 公吨的体重估计。将体重与前庭迷路的半规管半径进行比较表明，马氏拉美西斯龙符合之前对现存哺乳动物和长颈鹿巨龙的研究中发现的比例关系。与长颈鹿巨龙一样，前半规管明显大于比例关系所预测的大小，这表明头部在矢状面上的敏感度更高，运动速度更慢。
