The Extinct Sloth Lemurs of Madagascar

Evolutionary Anthropology 12:252–263 (2003) ARTICLES The Extinct Sloth Lemurs of Madagascar LAURIE R. GODFREY AND WILLIAM L. JUNGERS Paleontological expeditions to Madagascar over the past two decades have deed, Alfred Grandidier,5–7 the West- yielded large quantities of bones of extinct lemurs. These include abundant post- ern scientist credited with discovering cranial and cranial remains of new species belonging to a group of giant extinct Ambolisatra, the first subfossil site, lemurs that we have called sloth lemurs due to their remarkable postcranial needed only to follow the led of a vil- convergence with arboreal sloths. New fossils have come from a variety of loca- lage headman to a marsh in south- tions in Madagascar, including caves in the Northwest (Anjohibe) and the Ankarana western Madagascar in which, he was Massif, located in the extreme north, as well as pits in the karstic plains near Toliara assured, the bones of the “Song’aomby” in southwestern Madagascar. The most spectacular of these is the extremely deep (literally, the “cow that isn’t a cow,” or pit (Ͼ100 m) called Ankilitelo, the “place of the three kily trees.” These new pygmy hippopotamus) could be found materials provide insights into the adaptive diversity and evolution of sloth lemurs. (Box 1). Among the bones that Grandi- New carpal and pedal bones, as well as vertebrae and other portions of the axial dier retrieved from that marsh in 1868 skeletons, allow better reconstruction of the positional behavior of these animals. was the distal humerus of a sloth le- New analytical tools have begun to unlock the secrets of life-history adaptations of mur, Palaeopropithecus—perhaps the the Palaeopropithecidae, making explicit exactly what they had in common with first specimen of a giant extinct lemur their relatives, the Indriidae. Paleoecological research has elucidated the contexts to be examined by a Western scientist. in which they lived and the likely causes of their disappearance. It was not described until decades later,8 and its association with sloth lemur skulls remained obscure for de- The sloth lemurs, or Palaeopro- in body size of all families of Malagasy cades more. But no longer could there pithecidae, comprise four of the eight lemurs (from under 10 kg to over 200 be any doubt that fabulous mega- recognized genera of extinct lemurs kg) and the most extreme modifica- beasts once thrived in Madagascar. and more than a third of the extinct tion of the hind limb and axial skele- The nomen Palaeopropithecus in- species (Table 1; Figs. 1 and 2). Four ton. The elongation of the forelimb gens was allocated to a mandible genera are currently recognized as be- and reduction of the hind limb are all found at another subfossil site in longing in this family: Palaeopropithe- the more remarkable because their southwestern Madagascar just before cus (the type genus), the truly gigantic closest relatives, the Indriidae, have the turn of the twentieth century.9 The Archaeoindris, the much smaller-bod- some of the longest hindlimbs and mandible was chimp-sized but had si- ied Mesopropithecus, and the mid- shortest forelimbs in the Order Pri- faka-like teeth. Similar mandibles and sized, recently discovered Babakotia. mates. A sister taxon relationship of associated skulls were recovered from This family exhibits the greatest range the Palaeopropithecidae to the Indri- a marsh site, Ampasambazimba, in idae is supported by molecular data1 the interior of the island, and Palaeo- and a host of dental morphological propithecus maximus was named.10 and developmental specializations. Postcranial bones were assigned to Western scientists first learned of Palaeopropithecus, almost always in- Laurie R. Godfrey is Professor of Anthro- the existence of giant mammals on the correctly. pology at the University of Massachusetts at Amherst. [email protected] island of Madagascar in the mid-sev- Other whole or partial crania with William L. Jungers is Professor of Anatom- enteenth century through the writings sifaka-like teeth were recovered at ical Sciences at Stony Brook University, New York. [email protected] of French colonial governor Etienne Ampasambazimba in the early 1900s. Both have been working on the evolution, de Flacourt. In addition to providing They ranged dramatically in size: ecomorphology, and extinction of pri- his own descriptions of the biota of Some (Mesopropithecus pithecoides)10 mates in Madagascar for the last three 2 decades. Both have collaborated on pa- Madagascar, Flacourt recorded puta- were barely larger than the crania of leontological expeditions in Madagascar tive Malagasy eyewitness accounts of diademed sifakas, while others (Ar- with Elwyn L. Simons at Duke University huge and dangerous beasts roaming chaeoindris fontoynontii)11 rivaled the and David Burney at Fordham University. the Great Red Island. In some rural size of gorilla crania. The gorilla-sized regions of Madagascar, even today, as Archaeoindris was established on the © 2003 Wiley-Liss, Inc. during the past hundred years, stories basis of a mandible and two fragmen- DOI 10.1002/evan.10123 Published online in Wiley InterScience of hornless “water cows” and other tary maxillae. A femur belonging to (www.interscience.wiley.com). large creatures can be heard.3,4 In- Archaeoindris was attributed to an- ARTICLES Sloth Lemurs of Madagascar 253 TABLE 1. Taxonomy of the Sloth Lemurs Palaeopropithecus as an aquatic crea- Family Palaeopropithecidae (Tattersall, 1973) ture, swimming at the water’s surface Genus Palaeopropithecus (G. Grandidier, 1899) with its eyes, ears, and nostrils barely Palaeopropithecus ingens (G. Grandidier, 1899) above water. Such behavior, Standing Palaeopropithecus maximus (Standing, 1903) believed, could explain not merely the [Palaeopropithecus sp. nov.] elevation of the nasals and the upward Genus Archaeoindris (Standing, 1909) Archaeoindris fontoynontii (Standing, 1909) orientation of the axes of the orbits, Genus Babakotia (Godfrey and coworkers, 1990) but also the alignment of the nasal Babakotia radofilai (Godfrey and coworkers, 1990) aperture, orbits, and external auditory Genus Mesopropithecus (Standing, 1905) meatus in a plane perpendicular to Mesopropithecus pithecoides (Standing, 1905) that of the occipital condyles, the Mesopropithecus globiceps (Lamberton, 1936) “elongation” and “flattening” of the Mesopropithecus dolichobrachion (Simons and coworkers, 1995) skull, the narrowing of the postorbital region, the flattening of the bullae, other lemur species, Lemuridother- nial and postcranial features. On the and the placement of the lacrimal ium.12 The only known cranium and basis of its cranium, paleontologist fossa inside the orbital rim (Fig. 3). possibly associated mandible of Ar- Herbert F. Standing25 reconstructed Standing25 believed that the postcra- chaeoindris were discovered much later at Ampasambazimba.13 In the 1930s, Charles Lamberton launched a series of paleontological expeditions (mainly in the Southwest) that were to add to the list of recognized species of extinct lemurs. In 1936 he described, at first under another genus name, additional crania belonging to Mesopropithecus.14,15 In 1938, Decary16 recovered specimens belonging to a new species of Palaeo- propithecus at Anjohibe, but the uniqueness of these specimens was not recognized at the time. In 1965, Mahe´17 found additional specimens of the same species at Amparihingidro in the Northwest. Yet more species of sloth lemurs were discovered in the late twentieth century. Beginning in the early 1980s, Elwyn Simons18–20 launched a series of expeditions to central, northwestern, northern, and southwestern Madagascar. Among the more spectacular discoveries of Si- mons and his team were those of a nearly complete skeleton of the new species of Palaeopropithecus from the northwest21,22; a new genus and species of giant lemur, Babakotia radofilai, from the north and northwest23; and a new species of Mesopropithecus (M. dolichobrachion) from the extreme north.24 BEHAVIORAL RECONSTRUCTION OF THE SLOTH LEMURS Early reconstructions of the life ways of Palaeopropithecus and other giant lemurs were confounded by postcranial misattributions as well as Figure 1. Map of Madagascar, showing the known geographic distributions of sloth lemur fanciful interpretations of both cra- species, and highlighting selected subfossil sites. 254 Godfrey and Jungers ARTICLES imba for those of Mesopropithecus pithecoides and somehow took these to imply monkey likenesses. Refer- ences to Archaeoindris as being similar to Megaladapis in its locomotor behavior were also based, at least in part, on attributional errors.31 Inter- pretations of the locomotion of Ar- chaeoindris were hampered as well by a dearth of specimens. Only six postcrania belonging to Archaeoindris have ever been found: a damaged humerus, the “Lemuridotherium” femur, and four shafts of the long bones of an immature individual. Postcrania of Mesopropithecus are better repre- In addition to providing his own descriptions of the biota of Madagascar, Flacourt Figure 2. Working cladogram for the Indriidae and the Palaeopropithecidae. The Palaeo- propithecidae share a host of postcranial characteristics that bear testimony to their slow recorded putative climbing and suspensory habits (see text). They can also be distinguished craniodentally from the Indriidae, their closest relatives, by the increased lateral flare and greater robus- Malagasy eyewitness ticity of the zygoma, stronger postorbital constriction, more

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