Cuff Andrew R, Rayfield Emily J
School of Earth Sciences, University of Bristol , Bristol , United Kingdom.
PeerJ. 2015 Jul 9;3:e1093. doi: 10.7717/peerj.1093. eCollection 2015.
Ornithomimosaur dinosaurs evolved lightweight, edentulous skulls that possessed keratinous rhamphothecae. Understanding the anatomy of these taxa allows for a greater understanding of "ostrich-mimic" dinosaurs and character change during theropod dinosaur evolution. However, taphonomic processes during fossilisation often distort fossil remains. Retrodeformation offers a means by which to recover a hypothesis of the original anatomy of the specimen, and 3D scanning technologies present a way to constrain and document the retrodeformation process. Using computed tomography (CT) scan data, specimen specific retrodeformations were performed on three-dimensionally preserved but taphonomically distorted skulls of the deinocheirid Garudimimus brevipesBarsbold, 1981 and the ornithomimids Struthiomimus altusLambe, 1902 and Ornithomimus edmontonicusSternberg, 1933. This allowed for a reconstruction of the adductor musculature, which was then mapped onto the crania, from which muscle mechanical advantage and bite forces were calculated pre- and post-retrodeformation. The extent of the rhamphotheca was varied in each taxon to represent morphologies found within modern Aves. Well constrained retrodeformation allows for increased confidence in anatomical and functional analysis of fossil specimens and offers an opportunity to more fully understand the soft tissue anatomy of extinct taxa.
似鸟龙类恐龙演化出了轻巧、无牙且带有角质喙的头骨。了解这些类群的解剖结构有助于更深入地理解“鸵鸟模仿者”恐龙以及兽脚亚目恐龙演化过程中的特征变化。然而，化石形成过程中的埋藏学过程常常会扭曲化石残骸。逆向变形提供了一种恢复标本原始解剖结构假说的方法，而三维扫描技术则提供了一种限制和记录逆向变形过程的途径。利用计算机断层扫描（CT）数据，对三维保存但在埋藏学上变形的恐爪龙类短吻加鲁迪米（Garudimimus brevipes Barsbold，1981）、似鸟龙类阿尔塔斯氏似鸟龙（Struthiomimus altus Lambe，1902）和埃德蒙顿似鸟龙（Ornithomimus edmontonicus Sternberg，1933）的头骨进行了特定标本的逆向变形。这使得可以重建内收肌组织，然后将其映射到头骨上，据此计算逆向变形前后的肌肉机械优势和咬合力。在每个类群中改变喙的范围，以呈现现代鸟类中发现的形态。受到充分限制的逆向变形增加了对化石标本进行解剖学和功能分析的信心，并提供了一个更全面了解已灭绝类群软组织解剖结构的机会。
