Bone histology of the giant fossil dormouse Hypnomys onicensis (Gliridae, Rodentia) from Balearic Islands

Insular gigantism is frequent in fossil and extant micromammals. It is widely assumed to result from increased food availability through expanded dietary niches under decreased interspecific competition. We compared the bone histology of the fossil giant dormouse Hypnomys onycensis (Gliridae) from the Balearic Islands with that of its closest living relative, Eliomys quercinus. Both display the same bone tissue types at similar ontogenetic stages, indicating comparable growth rates. Skeletochronological analysis shows that Hypnomys had an exceptionally long lifespan. Gigantism in insular Hypnomys hence results from a shift in life history toward the slow end of the slow–fast continuum.