A Preliminary Comparison of Morphological Features of the Extinct Giant Aye-Aye (Daubentonia robusta

The aye-aye (Daubentonia) is a monotypic genus belonging to the Primate suborder, Prosimii. There is one extant species, D. madagascariensis (D. mad.), in Madagascar, and it is known for its distinct anatomic structure. Aye-ayes have large ever-growing incisors and an elongated tapping finger, which allows for their unique foraging behavior. Subfossils dating to less than ~1,000 years ago of a giant version of the present day aye-aye were found in arid environments in the south and southwest regions of Madagascar (Simons 1994). They were brought back to the Institut de Paléontologie in Paris, and were identified as belonging to the species, D. robusta (Simons 1994). In this study, a comparison of dimensions and robusticity of the anatomy of the extinct and extant aye-ayes was undertaken. Digital calipers were used on digital micro-computed tomography (micro-CT) scans of the subfossil bones to take measurements such as proximal-distal length and anterior-posterior width of the limb bones. Results were compared to measurements of the extant aye- aye taken from the literature. The size, robusticity, and inferred locomotor patterns of the two species were compared. In addition to having longer limbs, D. robusta was ~1.2 times more robust than D. madagascariensis. Due to this robusticity, the extinct aye-aye most likely moved slowly and was primarily terrestrial, compared to the extant form, whose lighter and more gracile limbs allow for more rapid locomotion and arboreality. Future research should include a comparison of the diets of the two Daubentonia species to see what additional differences exist that contribute to their size differences.