Tracing the origin of the panda´s thumb

ABELLA, JUAN ; PÉREZ-RAMOS, ALEJANDRO ; VALENCIANO, ALBERTO; ALBA, DAVID M.; ERCOLI, MARCOS DARÍO; HONTECILLAS, DANIEL ; MONTOYA, PLINIO; MORALES, JORGE

NATURWISSENSCHAFTEN

SPRINGER

Lugar: Berlin; Año: 2015 vol. 102

0028-1042

We investigate the relative development of thecarnivoran radial sesamoids to untangle the evolution of thisiconic structure. In the pandas (both giant and red), this ?falsethumb? is known to perform a grasping role during bamboofeeding in both the red and giant pandas. An original locomotorrole has been inferred for ailurids, but this remains to beascertained for ursids. A large sample of radial sesamoids ofIndarctos arctoides from the Miocene of Batallones-3 (Spain)indicates that this early ailuropodine bear displayed a relativelyhypertrophied radial sesamoid, with a configuration moresimilar to that of the red panda and other carnivorans than tothat of giant pandas. This false thumb is the first evidence ofthis feature in the Ursidae, which can be linked to a moreherbivorous diet. Moreover, in the two extant pandas, the falsethumb should not be interpreted as an anatomical convergence,but as an exaptive convergence regarding its use duringthe bamboo feeding, which changes the evolutionary view ofthis singular structure.