vulnerable to hunting and habitat loss. Etymology The generic name Archaeoindris, meaning "ancient indri-like lemur", is derived from the Greek word ἀρχαῖος (archaios, or "ancient") and indris, a common variation of the generic name Indri. The species name, fontoynontii (sometimes spelled fontoynonti), was selected in honor of Antoine Maurice Fontoynont, the president of the Académie Malgache (Malagasy Academy) at the time. Fontoynont was reported to have been supervising the excavation when it was discovered. Evolutionary history Archaeoindris was a type of sloth lemur (family Palaeopropithecidae), a recently extinct family of giant lemurs (known as subfossil lemurs) native to Madagascar. Its ancestors were likely arboreal (tree-dwelling), and this giant sloth lemur has been compared to the extinct giant ground sloths of North and South America. Archaeoindris was most closely related to Palaeopropithecus, a genus containing the second largest of the sloth lemurs and specialized for suspensory behavior in its arboreal habitat. Traits of the postcranium (skeleton below the skull) indicate that Babakotia was the next most closely related sloth lemur to Archaeoindris and Palaeopropithecus, followed by Mesopropithecus, the smallest of the sloth lemurs. All four genera of sloth lemurs are known to be a sister taxon (close relatives) of family Indriidae, which includes the indri (Indri), sifakas (Propithecus), and woolly lemurs (Avahi). This relationship is supported by data from morphological, developmental, and molecular research. Another member of this clade (related group) is the family of monkey lemurs (Archaeolemuridae). Dental features, such as the morphology of their molar teeth and the modified number of teeth in their toothcomb (a specialized grooming structure found in lemuriforms), have long suggested a relationship. However, other anatomical and developmental traits suggested that monkey lemurs might be more closely related to family Lemuridae, which include five genera of lemur, including the ring-tailed lemur (Lemur catta). Molecular analysis has shown strong support for the former, placing the monkey lemurs in a clade with the sloth lemurs and indriids. Taxonomic classification The family Palaeopropithecidae contained a large number of species compared to most other subfossil lemur families. It included four known genera and seven species, all of which are now extinct. Among these was the genus Archaeoindris, one of only a few monotypic lemur taxa. Archaeoindris fontoynontii was first described by Herbert F. Standing in 1909 from two fragments of a maxilla (upper jaw) and a complete mandible (lower jaw). These type specimens—AM-6239 (maxillae) and AM-6237 (mandible)—are stored in