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The present study compares the forefoot and hindfoot musculature of five representative species of Cavioidea rodents. In all species, the musculature of both forefeet and hindfeet have the same array regardless of the absence of digit I in the manus of Hydrochaeris hydrochaeris and Cavia porcellus. Our results suggest a tendency in these species towards a three-digit system, with a functional loss of digit V and a predominance of digit III in their forefeet. In the same way, the muscular reduction of digit I in the other rodents analyzed indicates a four-digit system with predominance of digit II in Myoprocta acouchy and Dasyprocta leporina and of digit V in Agouti paca. There seems to be an association between the muscular arrangement and functional axis of the foot, raising the general question why this axis runs between the third and forth digit, or along the third digit.

Armadillos comprise a particular group of armoured animals whose functional morphology of locomotion remains unclear. For the first time, the kinematic patterns of Dasypus novemcinctus are analysed. Eight specimens of nine‐banded armadillos were studied at a research institute in São Paulo State, Brazil. The individuals were induced to cross a horizontal corridor and each gait performed during the time each of them was kept inside this structure was recorded to a detailed analysis posteriorly performed in a computer program. Four parameters regarding speed range were considered: stride frequency (Hz) (1/stride period), stride length (m), speed (ms−1) and duty factor (%). A total of 89 strides have been analysed among symmetrical (60.6%) and asymmetrical gaits (39.4%), and six footfall patterns were here reported as follows: lateral sequences (symmetrical), transverse gallop, canter, bound, half‐bound and crutch walk (asymmetrical). This kind of analysis implements our knowledge on the locomotory aspects of these animals, hence contributing to the improvement of our knowledge on this still poorly known group. [ABSTRACT FROM AUTHOR]

The stance of pterosaurs on land is traditionally a controversial question. Here, we show that pterosaurs likeAnhanguera piscatorwere quadrupeds. An osteological model ofA. piscatorwas three-dimensionally built in digital space. The reconstructed muscles of its pelvic girdle were then placed on their points of origin and insertion to allow the biomechanical calculations to find the most efficient stance on land to be performed. The hindlimb readjustment (i.e. the repositioning of the hindlimb according to the achieved results) led to a pelvic counterclockwise displacement at 10°, which means that the ilium previously placed at 0° regarding an axis parallel to the ground was moved (and so the whole pelvis) 10° up from the preacetabular process. This new position preventsA. piscatorfrom having a fully upright stance. A 10° displacement of the pelvic girdle would compel the forelimbs to be highly sprawled. Therefore, this study affordsA. piscatorhaving a quadrupedal gait and demonstrates that a bipedal stance is not viable once the lever arm values decrease abruptly both for extensor and flexor muscles during the femoral extension. This is the first time this approach is used to shed light on this question. [ABSTRACT FROM PUBLISHER]