Department of Earth Sciences, University of Bristol, Bristol, United Kingdom.
PeerJ. 2022 Jan 24;10:e12810. doi: 10.7717/peerj.12810. eCollection 2022.
Sauropods are familiar dinosaurs, immediately recognisable by their great size and long necks. However, their necks are much less well known than is often assumed. Surprisingly few complete necks have been described in the literature, and even important specimens such as the Carnegie and , and the giant Berlin brachiosaur, in fact have imperfectly known necks. In older specimens, missing bone is often difficult to spot due to over-enthusiastic restoration. Worse still, even those vertebrae that are complete are often badly distorted-for example, in consecutive cervicals of the Carnegie CM 84, the aspect ratio of the posterior articular facet of the centrum varies so dramatically that C14 appears 35% broader proportionally than C13. And even in specimens where the cervicodorsal sequence is preserved, it is often difficult or impossible to confidently identify which vertebra is the first dorsal. Widespread incompleteness and distortion are both inevitable due to sauropod anatomy: large size made it almost impossible for whole individuals to be preserved because sediment cannot be deposited quickly enough to cover a giant carcass on land; and distortion of presacral vertebrae is common due to their lightweight hollow construction. This ubiquitous incompleteness and unpredictable distortion compromise attempts to mechanically analyze necks, for example to determine habitual neck posture and range of motion by modelling articulations between vertebrae.
蜥脚类恐龙是广为人知的恐龙,其巨大的体型和长长的脖子让人一眼就能认出来。然而,它们的脖子却远没有人们想象的那么为人熟知。实际上,在文献中描述的完整的蜥脚类恐龙脖子非常少,甚至像卡内基博物馆的和柏林的巨型腕龙这样的重要标本,其脖子实际上也是人们知之甚少的。在较古老的标本中,由于过度修复,缺失的骨头往往很难被发现。更糟糕的是,即使是那些完整的脊椎也经常严重变形——例如,在卡内基博物馆的 CM 84 连续颈椎中,椎体后部关节面的纵横比变化非常大,以至于 C14 看起来比 C13 宽 35%。甚至在那些保存了颈背序列的标本中,也很难或不可能确定哪一个椎体是第一个背椎。广泛的不完整性和变形都是蜥脚类恐龙解剖结构所不可避免的:由于体型庞大,几乎不可能保存完整的个体,因为沉积物没有足够快的速度覆盖陆地上的巨大尸体;并且由于其轻质的空心结构,前脊椎骨的变形很常见。这种无处不在的不完整性和不可预测的变形,使得试图通过模拟脊椎关节来对颈部进行机械分析变得困难,例如确定习惯性的颈部姿势和运动范围。