Cost Ian N, Sellers Kaleb C, Rozin Rachel E, Spates Anthony T, Middleton Kevin M, Holliday Casey M
Department of Pathology and Anatomical Sciences, University of Missouri, Columbia, MO 65211, USA.
Department of Biology, Albright College, Reading, PA 19612, USA.
J Exp Biol. 2022 Feb 15;225(Suppl1). doi: 10.1242/jeb.243216. Epub 2022 Feb 4.
Comparing patterns of performance and kinematics across behavior, development and phylogeny is crucial to understand the evolution of complex musculoskeletal systems such as the feeding apparatus. However, conveying 3D spatial data of muscle orientation throughout a feeding cycle, ontogenetic pathway or phylogenetic lineage is essential to understanding the function and evolution of the skull in vertebrates. Here, we detail the use of ternary plots for displaying and comparing the 3D orientation of muscle data. First, we illustrate changes in 3D jaw muscle resultants during jaw closing taxa the American alligator (Alligator mississippiensis). Second, we show changes in 3D muscle resultants of jaw muscles across an ontogenetic series of alligators. Third, we compare 3D resultants of jaw muscles of avian-line dinosaurs, including extant (Struthio camelus, Gallus gallus, Psittacus erithacus) and extinct (Tyrannosaurus rex) species to outline the reorganization of jaw muscles that occurred along the line to modern birds. Finally, we compare 3D resultants of jaw muscles of the hard-biting species in our sample (A. mississippiensis, T. rex, P. erithacus) to illustrate how disparate jaw muscle resultants are employed in convergent behaviors in archosaurs. Our findings show that these visualizations of 3D components of jaw muscles are immensely helpful towards identifying patterns of cranial performance, growth and diversity. These tools will prove useful for testing other hypotheses in functional morphology, comparative biomechanics, ecomorphology and organismal evolution.
比较不同行为、发育阶段和系统发育过程中的表现模式和运动学，对于理解诸如摄食器官等复杂肌肉骨骼系统的进化至关重要。然而，在整个摄食周期、个体发育途径或系统发育谱系中传达肌肉方向的三维空间数据，对于理解脊椎动物头骨的功能和进化至关重要。在这里，我们详细介绍了使用三元图来展示和比较肌肉数据的三维方向。首先，我们展示了美洲短吻鳄（密西西比鳄）在闭口时颌部肌肉合力的三维变化。其次，我们展示了在一系列短吻鳄个体发育过程中颌部肌肉合力的三维变化。第三，我们比较了鸟类谱系恐龙颌部肌肉的三维合力，包括现存物种（鸵鸟、原鸡、非洲灰鹦鹉）和已灭绝物种（霸王龙），以勾勒出沿着现代鸟类进化路线发生的颌部肌肉重组。最后，我们比较了样本中咬合力强的物种（密西西比鳄、霸王龙、非洲灰鹦鹉）颌部肌肉的三维合力，以说明在主龙类的趋同行为中如何运用不同的颌部肌肉合力。我们的研究结果表明，这些颌部肌肉三维组成部分的可视化对于识别颅骨表现、生长和多样性模式非常有帮助。这些工具将被证明对检验功能形态学、比较生物力学、生态形态学和生物进化中的其他假设有用。
