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Megaladapidae

Family

Description

Megaladapis, the sole genus of this family, contains three species, Megaladapis edwardsi, M. grandidieri, and M. madagascariensis, known collectively as the “koala lemurs.” Details of their molar teeth and various aspects of skull structure originally led experts to believe they were most closely related to the genus Lepilemur, but studies of ancient DNA now seem to indicate closer phylogenetic ties to the Lemuridae (A. Yoder, pers. comm.). Body weight estimates range from 45 to 85 kg (the heaviest being similar in weight to a female gorilla, see Figs. 3.4 and 3.14), and leaves were almost certainly the dietary staple for this group (Jungers et al., 2002; Godfrey et al., 2004a). The skull of Megaladapis is highly elongated, to a degree found in no other primate, and the face is tilted upwards and connected to a relatively small neurocranium via enormous frontal sinuses (Figs. 3.12 and 3.13). The hole through which the spinal cord exited from the braincase faces fully rearwards, as do the joint surfaces by which the skull articulated with the spine. In combination, these adaptations would have turned the long head into a functional extension of the neck, maximizing the radius within which this heavy animal could have cropped leaves from a single sitting position. Megaladapis would have eaten using the horny pad that presumably replaced the adult incisors that are missing in the front of the mouth; an overhanging shelf of bone above the nasal aperture also hints at the presence of a mobile snout (Fig. 3.12).

The body skeleton of Megaladapis was no less unusual (Figs. 3.12 and 3.13), apparently finding its closest analogue in the marsupial koala of Australia. Its extraordinarily long hands and feet, highly adapted for strong grasping, make very clear that it was an arboreal animal. However, its arms and legs were rather short, and, in combination with its high body weight, suggest that Megaladapis had very limited leaping abilities. Like the koala, these primates would have climbed slowly and cautiously in the trees (Figs. 3.1 and 3.12). Furthermore, they may well have adopted a variety of suspensory postures, perhaps emphasizing the hind limbs, since the feet were even more elongated and specialized for powerful grasping than were the hands. Specimens from the Ankilitelo pit cave in southwest Madagascar show that Megaladapis was alive 630–650 years ago (Simons et al., 1995), and based on Carbon-14 dates, this genus persisted in southwestern Madagascar until at least A.D. 1280–1420 (Burney et al., 2004).

Family order: 
4