Three‐Dimensional Musculoskeletal Modeling of the Sauropodomorph Hind Limb: The Effect of Postural Change on Muscle Leverage

Abstract

The biomechanical constraints for life at massive size can be directly observed in the evolutionary history of sauropodomorph dinosaurs. Members of this lineage underwent a number of major postural transitions as they increased in size from relatively small bipedal dinosaurs to massive titanosaurs that include the largest terrestrial animals of all time. To better understand the impact of gigantic size on the biomechanics of sauropods, we used three‐dimensional musculoskeletal modeling to investigate how hind limb musculature was affected, first by the development of a quadrupedal stance from a bipedal one, and later in the transition from a narrow‐gauge to a wide‐gauge stance. Muscle moment arms were measured in four sauropodomorph taxa: the bipedal basal sauropodomorph Plateosaurus engelhardti, the narrow‐gauge diplodocid Diplodocus carnegii, the titanosauriform Giraffatitan brancai, and the wide‐gauge titanosaur Diamantinasaurus matildae. In Plateosaurus, low moment arm leverage in the hip extensors and knee flexors and extensors was observed suggesting high‐velocity movement for fast locomotion. A reduction in hip extensor leverage in Diamantinasaurus was found which suggests a reduced role for the hind limb in forward propulsion in titanosaurs. An increase in overall hip adductor leverage and leverage of adductors 1 and 2 in Diamantinasaurus, compared with other taxa studied, might relate to the development of a wide‐gauge stance. High knee flexor–extensor leverage in Giraffatitan but not Diamantinasaurus partially refutes the idea that broader femoral condyles in titanosauriforms increased knee torque production capabilities. Sauropodomorph postural changes clearly had an impact on the function and leverage of hind limb muscles. Anat Rec, 301:2145–2163, 2018. © 2018 Wiley Periodicals, Inc.

Myological reconstruction of the pelvic girdle and hind limb of the giant titanosaurian sauropod dinosaurDreadnoughtus schrani

“…Scarcity of myological investigations of sauropods, in general, including well‐preserved and fairly complete titanosaurian taxa (e.g., Rapetosaurus , Curry Rogers, 2009; Saltasaurus , Powell, 2003), combined with a general lack of quantity and quality of preservation for the clade as a whole, has greatly limited our understanding of titanosaurian appendicular musculature. Only a few previous species‐level myological studies have been completed for members of Titanosauria (Borsuk‐Bialynicka, 1977; Ibiricu et al, 2018; Klinkhamer et al, 2018, 2019; Otero & Vizcaíno, 2008; Voegele et al, 2020). Alternatively, descriptions of sauropod appendicular material occasionally include discussion of probable osteological correlates for muscle attachment (e.g., Curry Rogers, 2009; Gallina & Apesteguía, 2015; Harris, 2007; Silva Junior et al, 2019).…”

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

“…3D musculoskeletal modeling has been used previously to evaluate muscle moment arms in dinosaurs, predominantly in the hind limbs of theropods (Hutchinson et al, 2005;Bates et al, 2012a) and ornithischians (Bates et al, 2012b;Maidment et al, 2014). This method has only recently been applied to the sauropodomorph hind limb (Klinkhamer et al, 2018) and forelimb (Otero et al, 2017). Otero et al (2017) investigated the transition from a bipedal to a quadrupedal posture; however, this method has not yet been applied to investigate other postural transitions in more derived sauropods.…”

Disentangling biological variability and taphonomy: shape analysis of the limb long bones of the sauropodomorph dinosaur Plateosaurus

“…They are, moreover, mixed with obvious taphonomically influenced variations, as they occur similarly in the same area. However, because the medial insertion of the caudofemoralis muscles remains preserved ( Gatesy, 1990 ; Langer, 2003 ; Fechner, 2009 ; Klinkhamer et al, 2018 ), these changes remain still biologically plausible, taken cautiously. Considering the variation of outline, two main morphologies are found, from a rounded and smoothly curved shape to sharper and angled one.…”

“…Because this anatomical feature occurs in both femora, it is more plausible that this is a biologically driven feature than a taphonomic one. This trochanter is the attachment of two major muscles (caudofemoralis longus and brevis) involved in sauropodomorph locomotion (notably hip extension; Klinkhamer et al, 2018 ; Persons & Currie, 2019 ). Persons & Currie (2019) proposed the hypothesis that the distal elongation of the trochanter with a pendant process resulted in a distal extension of the insertion of the caudofemoralis brevis, conferring better leverage.…”

“…Detected on the last PC of the analysis, the variation is too slight to distinguish two or more groups according to this parameter. Biologically speaking, such a variation potentially implies subtle variations in the moment arm of the iliofibularis muscle, notably involved in knee flexion ( Langer, 2003 ) and hip extension ( Klinkhamer et al, 2018 ). Again, a more distally placed insertion would give a better leverage action of the muscle.…”