DOI: 10.5061/dryad.7d7wm37xm
title: Data from: Computational Modeling of Gluteus Medius Muscle Moment Arm in Caviomorph Rodents Reveals Ecomorphological Specializations

description: 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.
description: The files of this dataset contain bone models complete with 3D
 representations of the M. gluteus medius and its moment arm to the hip
 joint for 18 caviomorph rodent species. The files allow the assessment of
 instantaneous changes of moment arm lengths during modelled joint
 excursions. The bone models have been derived from CT scanning. All
 specimen numbers are provided in the main article.
description: We provide the data in two data formats: A)
 .fbx files can be opened with free and open-source 3D animation software
 Blender. B) .mb files can only be opened with
 proprietary software Autodesk Maya. However, for non-commercial purposes,
 Autodesk offers the usage of the software free of charge for members of
 educational institutions. We suggest using this software to work with the
 provided data.