Abstract:
Life underground has constrained the evolution of subterranean mammals to maximize
digging performance. However, the mechanisms modulating morphological change and
development of fossorial adaptations in such taxa are still poorly known. We assessed the
morpho-functional diversity and early postnatal development of fossorial adaptations (bone
superstructures) in the appendicular system of the African mole-rats (Bathyergidae), a highly
specialized subterranean rodent family. Although bathyergids can use claws or incisors for
digging, all genera presented highly specialized bone superstructures associated with
scratch-digging behavior. Surprisingly, Heterocephalus glaber differed substantially from other
bathyergids, and from fossorial mammals by possessing a less specialized humerus, tibia and
fibula. Our data suggest strong functional and developmental constraints driving the selection
of limb specializations in most bathyergids, but more relaxed pressures acting on the limbs of
H. glaber. A combination of historical, developmental and ecological factors in Heterocephalus
are hypothesized to have played important roles in shaping its appendicular phenotype.
