Running of the feathertail glider (Acrobates pygmaeus) on level ground: Kinematics.

A complete kinematic analysis of the trunk and limbs was performed for the smallest gliding mammal, the feathertail glider (Acrobates pygmaeus). To compare the running technique of the glider with that of terrestrial mammals, only movement on horizontal substrate was studied. Kinematic analysis was performed separately for bound with extended suspension and bound with both suspensions. Terrestrial locomotion of the feathertail glider was classified as primitive ricochet, which is distinguished from true gallop by the absence of a delay in protraction of the hindlimbs after their take-off. The kinematic analysis showed significant impacts of gliding adaptation on the quadrupedal running, the most striking of which are the extremely sprawling position of the limbs, in particular, the wide stance of the forelimbs, and consequently, the absence of crossing of the fore- and hindlimbs in gathered stage of the cycle. The degree of limbs' sprawling in the feathertail glider is closer to the reptilian condition than to the mammalian parasagittal state. The sprawling condition of the feathertail glider is secondary and therefore is designated as "deparasagittalization."