Klinkhamer, Ada J

Mallison, Heinrich

Poropat, Stephen F

Sloan, Trish

Wroe, Stephen

2019-05

The evolution of extraordinarily large size among Sauropoda was associated with a number of biomechanical adaptations. Changes in muscle moment arms undoubtedly accompanied these adaptations, but since muscles rarely fossilize, our ability to understand them has been restricted. Here, we use three-dimensional (3D) musculoskeletal modeling to reconstruct and quantitatively assess leverage of forelimb muscles in the transition from the narrow-gauge stance of basal sauropods to a wide-gauge stance in titanosaurs. A comparative analysis is conducted on three neosauropods: the narrow-gauge diplodocid <i>Apatosaurus louisae</i>, the intermediate-gauge titanosariform <i>Giraffatitan brancai</i>, and the wide-gauge titanosaur <i>Diamantinasaurus matildae</i>. In this study, moment arm magnitudes and corresponding morphological evidence indicates multiple changes across the narrow-gauge to wide-gauge transition in sauropods. High shoulder adduction was found in <i>Diamantinasaurus</i>, suggesting functional changes for supporting a wider stance and a limb less aligned with ground reaction force. High leverage in shoulder extension of <i>Diamantinasaurus</i> and <i>Giraffatitan</i> is possibly related to the increased use of the forelimb in forward propulsion with an anterior shift in center of mass. In addition, the prominence of the olecranon process in <i>Diamantinasaurus</i> produced high moment arm leverage in elbow flexion and extension, suggesting titanosaurs might have maintained a more flexed forelimb posture and displayed an increased degree of maneuverability. Other results are more variable between taxa but still indicate smaller scale changes. A sensitivity analysis was also conducted to measure the reliability of our models and test specific uncertainties within the modeling process, as well as other uncertainties uncovered during analysis.

The Anatomical Record, 302(5), p. 794-817

1932-8494

1932-8486

30315633

https://hdl.handle.net/1959.11/30577

en

John Wiley & Sons, Inc

Comparative Three-Dimensional Moment Arm Analysis of the Sauropod Forelimb: Implications for the Transition to a Wide-Gauge Stance in Titanosaurs

Journal Article

Publication