Data from: Computational Modeling of Gluteus Medius Muscle Moment Arm in Caviomorph Rodents Reveals Ecomorphological Specializations

The data stored in this repository allow the reproduction of the study
described in the following. Vertebrate musculoskeletal locomotion is
realized through lever-arm systems. The instantaneous muscle moment arm
(IMMA), which is expected to be under selective pressure and thus of
interest for ecomorphological studies, is a key aspect of these systems.
The IMMA changes with joint motion and its length change is technically
difficult to acquire—usually, proxies such as osteological in-levers are
used instead—and has not been compared in a larger phylogenetic
ecomorphology framework, yet. We used 18 species of the ecologically
diverse clade of caviomorph rodents to test whether its diversity is
reflected in the IMMA of the hip extensor M. gluteus medius. A large IMMA
is beneficial for torque generation; a small IMMA facilitates fast joint
excursion. We expected large IMMAs in scansorial species, small IMMAs in
fossorial species, and somewhat intermediate IMMAs in cursorial species,
depending on the relative importance of acceleration and joint angular
velocity. We modelled the IMMA over the entire range of possible hip
extensions and applied macroevolutionary model comparison to selected
joint poses. We also obtained the osteological in-lever of the M. gluteus
medius to compare it to the IMMA. At small hip extension, the IMMA was
largest on average in scansorial species, while the other two lifestyles
were similar. We interpret this as an emphasized need for increased hip
joint torque when climbing on inclines, especially in a crouched posture.
Cursorial species might benefit from a fast joint excursion, but their
similarity with the fossorial species is difficult to interpret and could
hint at ecological similarities. At larger extension angles, cursorial
species displayed the second-largest IMMAs after scansorial species. The
larger IMMA optimum results in powerful hip extension which coincides with
forward acceleration at late stance beneficial for climbing, jumping, and
escaping predators. This might be less relevant for a fossorial lifestyle.
The results of the in-lever only matched the IMMA results of larger hip
extension angles, suggesting that the modelling of the IMMA provides more
nuanced insights into adaptations of musculoskeletal lever arm systems
than this osteological proxy.