page_title: Pachylemur
section_title: Anatomy and physiology
hierarchical_section_title: Pachylemur / Anatomy and physiology
caption_attribution_description: English: Skull of the extinct lemur, Pachylemur insignis
context_page_description: Pachylemur is an extinct, giant lemur most closely related to the ruffed lemurs of genus Varecia. Two species are known, Pachylemur insignis and Pachylemur jullyi, although there is some doubt as to whether or not they may actually be the same species. Pachylemur is sometimes referred to as the giant ruffed lemur, because although it and the living ruffed lemurs had similar teeth and skeletons, Pachylemur was more robust and as much as three to four times larger. DNA studies have confirmed a sister group relationship between these two types of lemur. Like living ruffed lemurs, Pachylemur specialized in eating fruit, and was therefore an important seed disperser, possibly for tree species with seeds too large for even ruffed lemurs to swallow. In the spiny thickets of southwestern Madagascar, they were also likely to have dispersed seeds evolved to attach to fur and be carried away. Unlike ruffed lemurs, the fore- and hindlimbs of Pachylemur were nearly the same length, and therefore it was likely to be a slow, deliberate climber. However, both used hindlimb suspension to reach fruit on small branches below them.
context_section_description: Pachylemur resembled the living ruffed lemurs but was three or four times larger, with an estimated body mass of 10 kg (22 lb) for P. insignis and 13 kg (29 lb) for the larger P. jullyi. In addition, the skeleton is more robust.
  The dental formula is , as in all lemurids. The toothcomb—a comblike structure formed by the lower front teeth, characteristic of lemurs and lorisoids—is similar to that of other lemurids. The two halves of the mandible (lower jaw) do not fuse at the mandibular symphysis. However, there are some differences in tooth morphology from the living brown and ring-tailed lemurs, similar to those between the ruffed lemurs and the other genera. In Pachylemur, the talonid basin (a basin at the back end of the lower molars) is more elongate, and it is not lined by an entoconid cusp. In the first two upper molars, the lingual cingulum (a shelf on the inner, or lingual, side of the tooth) is expanded towards the front. The two species differ in details of tooth morphology. P. insignis had narrower lower premolars and molars, and the buccal (outer) cusps on these teeth are located to the front of their lingual counterparts. Relative to the ruffed lemurs, Pachylemur has more massive jaws and larger molars.
  The skull of Pachylemur is relatively broad, but the orbits (eye sockets) are smaller and oriented more towards the front than in the ruffed lemurs. In the postcranial skeleton, the most distinctive traits of Pachylemur are found. It had shorter and more robust limbs than the ruffed lemurs, and the fore- and hindlimbs were closer in length (intermembral index of approximately 97).
  Compared to the axial skeleton of ruffed lemurs, the vertebrae of Pachylemur had shorter vertebral bodies and the spinous process had less anticliny.  The head of its femur (thigh bone) was also relatively large.  As of 2001, no bones of the digits had been found for either species.
caption: The skull and teeth of Pachylemur insignis suggest that it ate mostly fruit and some leaves.
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