Department of Geology, Rowan University, Glassboro, NJ, USA.
Section of Vertebrate Paleontology, Carnegie Museum of Natural History, Pittsburgh, PA, USA.
J Anat. 2021 Mar;238(3):576-597. doi: 10.1111/joa.13334. Epub 2020 Oct 20.
Osteological correlates preserve more readily than their soft tissue counterparts in the fossil record; therefore, they can more often provide insight into the soft tissue anatomy of the organism. These insights can in turn elucidate the biology of these extinct organisms. In this study, we reconstruct the pelvic girdle and hind limb musculature of the giant titanosaurian sauropod Dreadnoughtus schrani based on observations of osteological correlates and Extant Phylogenetic Bracket comparisons. Recovered fossils of Dreadnoughtus exhibit remarkably well-preserved, well-developed, and extensive muscle scars. Furthermore, this taxon is significantly larger bodied than any titanosaurian for which a myological reconstruction has previously been performed, rendering this contribution highly informative for the group. All 20 of the muscles investigated in this study are sufficiently well supported to enable reconstruction of at least one division, including reconstruction of the M. ischiocaudalis for the first time in a sauropod dinosaur. In total, 34 osteological correlates were identified on the pelvic girdle and hind limb remains of Dreadnoughtus, allowing the reconstruction of 14 muscles on the basis of Level I or Level II inferences (i.e., not Level I' or Level II' inferences). Comparisons among titanosaurians suggest widespread myological variation, yet potential phylogenetic and other paleobiologic patterns are often obscured by fragmentary preservation, infrequent myological studies, and lack of consensus on the phylogenetic placement of many taxa. However, a ventrolateral accessory process is present on the preacetabular lobe of the ilium in all of the largest titanosauriforms that preserve this skeletal element, suggesting that the presence of this process (representing the origin of the M. puboischiofemoralis internus part II) may be associated with extreme body size. By identifying such myological patterns among titanosauriforms, we can begin to address specific evolutionary and biomechanical questions related to their skeletal anatomy, how they were capable of leaving wide-gauge trackways, and resulting locomotor attributes unique to this clade.
骨骼遗骸比软组织在化石记录中更易保存，因此它们更能深入了解生物体的软组织解剖结构。这些见解反过来又可以阐明这些灭绝生物的生物学特性。在这项研究中，我们基于骨骼遗骸的观察结果和现存的系统发育框架比较，重建了巨型泰坦巨龙巨龙龙的骨盆带和后肢肌肉组织。巨龙龙的化石保存完好，发育良好，肌肉痕迹广泛。此外，该种龙的体型明显大于以前任何一种已进行肌肉重建的泰坦巨龙，这一贡献为该类群提供了高度有价值的信息。在这项研究中调查的 20 块肌肉都得到了充分的支持，足以进行重建，包括首次在蜥脚类恐龙中重建 M. ischiocaudalis 肌肉。在巨龙龙的骨盆带和后肢遗骸上共确定了 34 个骨骼遗骸，可根据一级或二级推断（即不是一级'或二级'推断）重建 14 块肌肉。在泰坦巨龙之间的比较表明存在广泛的肌肉变化，但潜在的系统发育和其他古生物学模式往往因保存不完整、肌肉研究不频繁以及许多分类单元的系统发育位置缺乏共识而变得模糊。然而，在所有保存有这块骨骼的最大泰坦巨龙中，前髋臼叶的髂骨上都有一个腹外侧副突，这表明这个过程（代表 M. puboischiofemoralis internus part II 的起源）的存在可能与体型巨大有关。通过确定泰坦巨龙中的这种肌肉模式，我们可以开始解决与它们的骨骼解剖结构、它们如何能够留下宽轨距足迹以及由此产生的独特运动属性有关的特定进化和生物力学问题。
