New papers not yet mentioned:
Emil Krupandan, Anusuya ChinsamyâTuran Â& Diego Pol (2018)
The Long Bone Histology of the Sauropodomorph, Antetonitrus ingenipes.
The Anatomical Record 301(9): 1506-1518
This analysis of the long bone microstructure of Antetonitrus ingenipes fills a crucial gap in our understanding of the growth dynamics of sauropodomorph dinosaurs. The bone histology of basal Sauropodomorpha are often characterized by zonal tissue, and contrasts with that of more derived sauropod taxa which show a shift toward the deposition of uninterrupted fibrolamellar bone (with lines of growth being either absent or only present in the outer circumferential layer). In Antetonitrus, growth patterns in the youngest individuals exhibit uninterrupted fibrolamellar bone without any growth marks. Subâadult individuals, also exhibit highly vascularized fibrolamellar bone throughout the cortex, as in more derived Sauropods and Mussaurus, but growth lines occur intermittently (although not regularly) throughout the cortex as in Lessemsaurus. This indicates that Antetonitrus does not exhibit the growth dynamics previously considered characteristic of Sauropoda. Despite this, the largest (and possibly the oldest femur, NMQR 1705/163) does show an incipient external fundamental system (EFS). Our findings further suggest that growth marks are decoupled from bone size, which indicates a level of developmental plasticity in this taxon. Modulations or textural shifts in the pattern of vascular channel arrangements throughout the fibrolamellar bone in the cortex may be related to periods of resource limitations, although the lack of consistency of these modulations suggest that it is unlikely due to seasonal fluctuations. Localized bands of radial fibrolamellar bone, followed by resumption of normal growth in two samples are interpreted as evidence of a disease infliction, and subsequent recovery thereof.Â
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Ada J. Klinkhamer, Heinrich Mallison, Stephen F. Poropat, Trish Sloan & Stephen Wroe (2018)
Comparative threeâdimensional moment arm analysis of the sauropod forelimb: Implications for the transition to a wideâgauge stance in titanosaurs.
The Anatomical Record (advance online publication)
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 fossilise, our ability to understand them has been restricted. Here, we use threeâdimensional (3D) musculoskeletal modelling to reconstruct and quantitatively assess leverage of forelimb muscles in the transition from the narrowâgauge stance of basal sauropods to a wideâgauge stance in titanosaurs. A comparative analysis is conducted on three neosauropods: the narrowâgauge diplodocid Apatosaurus louisae, the intermediateâgauge titanosariform Giraffatitan brancai and the wideâgauge titanosaur Diamantinasaurus matildae. In this study moment arm magnitudes and corresponding morphological evidence indicates multiple changes across the narrowâgauge to wideâgauge transition in sauropods. High shoulder adduction was found in Diamantinasaurus, suggesting functional changes for supporting a wider stance and a limb less aligned with ground reaction force. High leverage in shoulder extension of Diamantinasaurus and Giraffatitan is possibly related to the increased use of the forelimb in forward propulsion with an anterior shift in centre of mass. In addition, the prominence of the olecranon process in Diamantinasaurus 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 manoeuvrability. Other results are more variable between taxa but still indicate smaller scale changes. A subjectivity analysis was also conducted to measure the reliability of our models and test specific uncertainties within the modelling process, as well as other uncertainties uncovered during analysis.