INVESTIGADORES
POL Diego
congresos y reuniones científicas
Título:
Forelimb biomechanics of Mussaurus patagonicus (Dinosauria, Sauropodomorpha): insights from three dimensional computer modeling
Autor/es:
OTERO, A.; HUTCHINSON, J.; POL, D.
Lugar:
Berlin
Reunión:
Congreso; 74° Annual Meeting of the Society of Vertebrate Paleontology; 2014
Resumen:
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We present a three-dimensional (3D)
reconstruction and biomechanical analysis of the forelimb of the basal
sauropodomorph Mussaurus patagonicus, from the Late Triassic of southern Patagonia, Argentina. Mussaurus has been interpreted as
more closely related to derived sauropodomorphs (i.e., Sauropodiformes) than to
more basal forms (e.g., Plateosaurus). 3D data were acquired with a laser scanner, and 3ds Max software was
used to estimate the positions and axes of the joints between bones and the
ranges of motion (ROMs) of each joint. Finally, we integrated the whole
forelimb into a musculoskeletal model in reasonably well-validated biomechanics
software (SIMM), producing the first such complete model of an archosaur forelimb.
The musculoskeletal model includes a
full range of degrees of freedom in joint rotation: flexion/extension,
ab/adduction, and long-axis rotation, using joint morphology to estimate more
realistic axes that could be non-orthogonal and not aligned to the world
coordinate system or main body axes. Also, we reconstructed 28 muscle groups
crossing the glenoid, elbow, and wrist joints. We used this model to estimate
all major muscle moment arms about the main limb joints, varying limb
orientation to quantify how these changed. Two forelimb models were analyzed,
considering the two current hypotheses about antebrachium architecture to
evaluate biomechanical differences between these: with manus pronation and with
no pronation.
Our analysis of joint articulations
indicates that the forelimb of Mussaurus was capable of similar ROMs for the gleno-humeral and phalangeal joints in
both models, differing in the elbow and wrist joints, which produced different
ROMs in each model. In this sense, the model with a pronated manus presented a
larger elbow ROM due to a better fit of the radius to the cuboid fossa of the
humerus. Wrist ROM, on the other hand was larger in the model with no
pronation.
The antebrachium was not capable of
active pronation, with minimal radial rotation against the ulna. The muscle
moment arm data are important for addressing how Mussaurus used the forelimbs, testing hypotheses of forelimb
function, such as locomotion, defense, grasping, and digging. We also present a
comparative analysis of these moment arms against data from extant Crocodylus (as a rough
approximation of plesiomorphic, quadrupedal musculoskeletal function), which
illuminates numerous potential changes of muscle actions from basal archosaurs
to bipedal - and then convergently quadrupedal - dinosaurs.