Pachylemur is an extinct, giant lemur most closely related to the ruffed lemurs of genusVarecia. 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.
Like other lemurs, Pachylemur was only found on the island of Madagascar, and its subfossil remains have been found primarily at sites in the central and southwestern parts of the island. Fragmentary and indeterminate remains have also been found in northern Madagascar. Pachylemur once lived in diverse lemur communities within its range, but in many of these locations, 20% or fewer of the original lemur species remain. Pachylemur went into decline following the arrival of humans in Madagascar around 350 BCE. Habitat loss, forest fragmentation, and bushmeat hunting are thought to have been the reasons for its disappearance. Pachylemur is thought to have gone extinct between 680 and 960 CE, although subfossil remains found in a cave pit in southwestern Madagascar may indicate that it survived up until 500 years ago.
Pachylemur was similar to but significantly larger and more robust than living ruffed lemurs (genusVarecia).[2][3] In addition to their general morphology, studies of their teeth (dental anatomy) also suggest a close relation.[4] In 1953, William Charles Osman Hill noted that the skull of both P.insignis and P.jullyi (then called Lemur insignis and L.jullyi) resembled that of ruffed lemurs more so than the rest of the lemurs classified in the genus Lemur at that time.[5]
Because of the similarities, Pachylemur is sometimes referred to as a giant ruffed lemur.[6] In addition to the morphological similarities, molecular studies also support a close relationship.[4] Based on studies of their DNA, Pachylemur and ruffed lemurs form the sister group relative to the rest of the lemurs in the family Lemuridae. This sister group itself forms a sister group with the clade (related group) containing brown lemurs (Eulemur), the ring-tailed lemur (Lemur), the greater bamboo lemur (Prolemur), and the lesser bamboo lemurs (Hapalemur).[1]
Taxonomic classification
French zoologist Henri Filhol was the first to scientifically describe a species of Pachylemur; he named Lemur insignis and Lemur intermedius in 1895 on the basis of a few subfossil bones.[7] Descriptions of other species now placed in Pachylemur quickly followed. In 1899, Guillaume Grandidier named a new genus and species, Palaeochirogalus jullyi,[lower-alpha 1] on the basis of two teeth from Antsirabe, central Madagascar, which he thought similar to dwarf lemurs (Cheirogaleus).[8] In 1903, Grafton Elliot Smith placed this species in the genus Lemur (as Lemur jullyi),[9] and in 1905, Grandidier himself considered the species a synonym of Lemur insignis.[10]
Meanwhile, in 1904, Herbert F. Standing had named a different species using the same name, Lemur jullyi,[13] and named another species Lemur maziensis.[14] He noted similarities between this group and the ruffed lemurs, then considered a single species, Lemur varius.[15] In 1908, Standing named another species in the group, Lemur majori,[16] and included his Lemur maziensis in L.jullyi.[17] The name Pachylemur was introduced for these animals in 1948 by Charles Lamberton, who grouped Lemur insignis, Lemur majori, and Lemur jullyi in a subgenus of the genus Lemur.[18]
Since 1979, Pachylemur has generally been regarded as a distinct genus, but some classifications include the genus in Lemur or the ruffed lemur genus Varecia.[19][20] In a 1982 review, Ian Tattersall recognized two species, Lemur insignis and Lemur jullyi. He did not regard Pachylemur as a distinct genus or even subgenus. As Tattersall noted, Lemur jullyi Standing, 1904, is preoccupied by Palaeochirogalus jullyi Grandidier, 1899, and thus invalid. However, both names are based on material from the central plateau of Madagascar and Tattersall therefore presumed that they belong to the same species, which he could continue to call Lemur jullyi.[21] Recent classifications recognize Pachylemur as a valid genus with two species—P.insignis (Filhol, 1895) and P.jullyi (Grandidier, 1899)—but express doubt about the distinction between the two species.[4][19]
There are several nomenclatural problems with the current use of the name Pachylemur.[22] First, Filhol had himself used the name Pachylemur in 1874 for a group of primitive primates, including Adapis, that he considered intermediate between pachyderms and lemurs.[23] Several other authors mentioned this name in the 19th and early 20th centuries, but it is questionable that any rendered the name available under the rules of zoological nomenclature.[24] Still, this name potentially renders Pachylemur Lamberton, 1948, invalid under the Principle of Homonymy.[19] In addition, the generic name Palaeochirogalus Grandidier, 1899, predates Pachylemur Lamberton, 1948, by half a century and thus takes precedence under the Principle of Priority, and Pachylemur Lamberton is itself unavailable because Lamberton failed to select a type species.[25] To conserve the name Pachylemur, Jelle Zijlstra, Colin Groves, and Alex Dunkel submitted a petition to the International Commission on Zoological Nomenclature in 2011.[26] The petition asks the Commission to suppress the names Pachylemur Filhol, 1874, Pachylemur Palmer, 1904 (based on Filhol's name), and Palaeochirogalus Grandidier, 1899, and to make Pachylemur Lamberton, 1948, retroactively available with Lemur insignis as its type species.[27]
Anatomy and physiology
Restoration of Pachylemur insignis
Pachylemur resembled the living ruffed lemurs but was three or four times larger, with an estimated body mass of 10kg (22lb) for P.insignis and 13kg (29lb) for the larger P.jullyi.[4][28] In addition, the skeleton is more robust.[4]
The dental formula is 2.1.3.32.1.3.3, 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.[4] 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.[3] 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.[4] Relative to the ruffed lemurs, Pachylemur has more massive jaws and larger molars.[3]
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.[3][4] 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).[4]
Based on dental wear and the presence of dental caries,[31][32]Pachylemur was likely a fruit specialist, just like the closely related ruffed lemurs,[31][33][34] but unlike most of the other leaf-eating, extinct, giant lemurs of Madagascar.[32] Although it primarily ate fruit, it may have supplemented its diet with leaves and other foliage seasonally.[35] Its teeth were similar in appearance to that of ruffed lemurs, while its molars and uneven dental wear suggest that it ate fewer leaves and more hard fruits and stems than today's brown lemur species.[31]
Pachylemur may have spread seeds of plants like Uncarina roeoesliana by carrying them on their fur.
Black-and-white ruffed lemurs can swallow seeds with a diameter up to 30 millimeters (1.2in), which is larger than any other living lemur. Having been more than twice as large, Pachylemur would have been capable of swallowing even larger seeds.[39] In the case of baobabs, the fruits have large seeds surrounded by a nutritious pulp and may have required seed dispersal through ingestion.[38] In western Madagascar, the genetic diversity of Commiphora guillaminii suggests it had more widespread seed dispersal in the past, but today shows signs of more localized diversity when compared to African species within the same genus that have not lost their seed dispersers.[39]
Many small trees and shrubs in the spiny thickets, such as endemicUncarina, conserve water by producing seeds with hooks and spines rather than fleshy fruits. These seeds attach themselves to the skin and fur of passing animals for dispersal, and are still dispersed by living lemur species as well as introduced species such as cattle. Pachylemur may also have helped disperse seeds in this fashion.[40]
For many years, palaeoanthropologists thought that Pachylemur was a ground-dwelling lemur due to its robust postcranial skeleton.[2] Yet more recent analysis of its axial and appendicular skeleton—particularly the vertebrae and femur—suggests that it was a tree-dweller (arboreal).[2][29] Like the ruffed lemurs, Pachylemur was also an arboreal quadruped that frequently exhibited hindlimb suspension in order to reach fruit and leaves on smaller branches. However, Pachylemur was a slow, deliberate climber unlike the ruffed lemurs, which leap and bound through the upper canopy.[41][42] Like both the living and extinct lemurs, Pachylemur likely conserved energy because of its diet, small brain, and slow climbing.[33]
Because its eyes were comparable in size to those of modern day-living (diurnal) lemurs, Pachylemur was probably diurnal as well, as were most of the giant, extinct lemurs. However, compared to similarly sized anthropoid primates, its visual acuity was relatively poor.[43]
In general, lemur diversity has declined since the arrival of humans due to habitat loss, forest fragmentation, and bushmeat hunting. At some subfossil sites, Pachylemur lived alongside as many as 19 or 20 other lemur species, but now as few as 20% of those species remain in those areas.[49]
Humans arrived in Madagascar around 350BCE, but did not cause the extinction of Pachylemur and the other giant lemurs immediately. Instead, many human-related factors, such as habitat loss, forest fragmentation, bushmeat hunting, and the introduction of invasive species, along with the gradual desiccation of certain parts of the island, caused their decline and eventual extinction over more than a millennium.[50] The same factors threaten all living lemur species today.[51]
The initial decline of Pachylemur began within 500years of human colonization, but prior to the establishment of large human settlements. Hunting in the Central Highlands and the spiny thickets likely caused a substantial drop in its population.[51] Large lemurs, including Pachylemur, survived in the Central Highlands, succulent woodlands, and spiny thickets until around 950CE.[51][52] Based on radiocarbon dating of subfossil remains collected as of 2010, the most recent remains of P.insignis out of 17dated specimens came from Ankilibehandry in the succulent woodlands and dated between 680 and 780CE. Of eight dated specimens, the most recent remains of P.jullyi came from Ampasambazimba in the Central Highlands and dated between 620 and 680CE.[53]Pachylemur is generally thought to have gone extinct between 680–960CE,[47] but remains of P.insignis have been found in Ankilitelo Cave (a pit cave in southwestern Madagascar), which is assumed to be less than 500years old.[54]
Lemuridae is a family of strepsirrhine primates native to Madagascar and the Comoros. They are represented by the Lemuriformes in Madagascar with one of the highest concentration of the lemurs. One of five families commonly known as lemurs. These animals were once thought to be the evolutionary predecessors of monkeys and apes, but this is no longer considered correct. They are formally referred to as lemurids.
Plesiorycteropus, also known as the bibymalagasy or Malagasy aardvark, is a recently extinct genus of mammals from Madagascar. Upon its description in 1895, it was classified with the aardvark, but more recent molecular evidence instead suggests that it is most closely related to the tenrecs. Two species are currently recognized, the larger P. madagascariensis and the smaller P. germainepetterae. They probably overlapped in distribution, as subfossil remains of both species have been found in the same site.
Archaeoindris fontoynontii is an extinct giant lemur and the largest primate known to have evolved on Madagascar, comparable in size to a male gorilla. It belonged to a family of extinct lemurs known as "sloth lemurs" (Palaeopropithecidae) and, because of its extremely large size, it has been compared to the ground sloths that once roamed North and South America. It was most closely related to Palaeopropithecus, the second largest type of sloth lemur. Along with the other sloth lemurs, Archaeoindris was related to the living indri, sifakas, and woolly lemurs, as well as the recently extinct monkey lemurs (Archaeolemuridae). The genus, Archaeoindris, translates to "ancient indri-like lemur", even though it probably became extinct recently, around 350 BCE.
Palaeopropithecus is a recently extinct genus of large sloth lemurs from Madagascar related to living lemur species found there today. Three species are known, Palaeopropithecus ingens, P. maximus, and P. kelyus. Radiocarbon dates indicate that they may have survived until around 1300–1620 CE. Malagasy legends of the tretretretre or tratratratra are thought to refer to P. ingens.
Mullerornis modestus is an extinct species of elephant bird, and the only member of the genus Mullerornis.
Cryptoprocta spelea, also known as the giant fossa, is an extinct species of carnivore from Madagascar in the family Eupleridae which is most closely related to the mongooses and includes all Malagasy carnivorans. It was first described in 1902, and in 1935 was recognized as a separate species from its closest relative, the living fossa. C. spelea was larger than the fossa, but otherwise similar. The two have not always been accepted as distinct species. When and how C. spelea became extinct is unknown; there is some anecdotal evidence, including reports of very large fossas, that there is more than one surviving species.
The monkey lemurs or baboon lemurs (Archaeolemuridae) are a recently extinct family of lemurs known from skeletal remains from sites on Madagascar dated to 1000 to 3000 years ago.
The sloth lemurs (Palaeopropithecidae) comprise an extinct family of lemurs that includes four genera. The common name can be misleading, as members of Palaeopropithecidae were not closely related to sloths. This clade has been dubbed the ‘‘sloth lemurs’’ because of remarkable postcranial convergences with South American sloths. Despite postcranial similarities, the hands and feet show significant differences. Sloths possess long, curved claws, while sloth lemurs have short, flat nails on their distal phalanges like most primates.
Archaeolemur is an extinct genus of subfossil lemurs known from the Holocene epoch of Madagascar. Archaeolemur is one of the most common and well-known of the extinct giant lemurs as hundreds of its bones have been discovered in fossil deposits across the island. It was larger than any extant lemur, with a body mass of approximately 18.2–26.5 kg (40–58 lb), and is commonly reconstructed as the most frugivorous and terrestrial of the fossil Malagasy primates. Colloquially known as a "monkey lemur," Archaeolemur has often been compared with anthropoids, specifically the cercopithecines, due to various morphological convergences. In fact, it was even misidentified as a monkey when remains were first discovered. Following human arrival to Madagascar just over 2000 years ago, many of the island’s megafauna went extinct, including the giant lemurs. Radiocarbon dating indicates that Archaeolemur survived on Madagascar until at least 1040-1290 AD, outliving most other subfossil lemurs.
Hadropithecus is a medium-sized, extinct genus of lemur, or strepsirrhine primate, from Madagascar that includes a single species, Hadropithecus stenognathus. Due to its rarity and lack of sufficient skeletal remains, it is one of the least understood of the extinct lemurs. Both it and Archaeolemur are collectively known as "monkey lemurs" or "baboon lemurs" due to body plans and dentition that suggest a terrestrial lifestyle and a diet similar to that of modern baboons. Hadropithecus had extended molars and a short, powerful jaw, suggesting that it was both a grazer and a seed predator.
Babakotia is an extinct genus of medium-sized lemur, or strepsirrhine primate, from Madagascar that contains a single species, Babakotia radofilai. Together with Palaeopropithecus, Archaeoindris, and Mesopropithecus, it forms the family Palaeopropithecidae, commonly known as the sloth lemurs. The name Babakotia comes from the Malagasy name for the indri, babakoto, to which it and all other sloth lemurs are closely related. Due to its mix of morphological traits that show intermediate stages between the slow-moving smaller sloth lemurs and the suspensory large sloth lemurs, it has helped determine the relationship between both groups and the closely related and extinct monkey lemurs.
Mesopropithecus is an extinct genus of small to medium-sized lemur, or strepsirrhine primate, from Madagascar that includes three species, M. dolichobrachion, M. globiceps, and M. pithecoides. Together with Palaeopropithecus, Archaeoindris, and Babakotia, it is part of the sloth lemur family (Palaeopropithecidae). Once thought to be an indriid because its skull is similar to that of living sifakas, a recently discovered postcranial skeleton shows Mesopropithecus had longer forelimbs than hindlimbs—a distinctive trait shared by sloth lemurs but not by indriids. However, as it had the shortest forelimbs of all sloth lemurs, it is thought that Mesopropithecus was more quadrupedal and did not use suspension as much as the other sloth lemurs.
Hypogeomys australis is an extinct rodent from central and southeastern Madagascar. First described in 1903, it is larger than its close relative, the living Hypogeomys antimena, which occurs further west, but otherwise similar. Average length of the femur is 72.1 mm, compared to 63.8 mm in H. antimena. One of the few extinct rodents of Madagascar, it survived to at least around 1536 BP based on radiocarbon dating. Little is known of its ecology, but it may have lived in burrows like its living relative and eaten some arid-adapted plants.
Subfossil lemurs are lemurs from Madagascar that are represented by recent (subfossil) remains dating from nearly 26,000 years ago to approximately 560 years ago. They include both extant and extinct species, although the term more frequently refers to the extinct giant lemurs. The diversity of subfossil lemur communities was greater than that of present-day lemur communities, ranging from as high as 20 or more species per location, compared with 10 to 12 species today. Extinct species are estimated to have ranged in size from slightly over 10 kg (22 lb) to roughly 160 kg (350 lb). Even the subfossil remains of living species are larger and more robust than the skeletal remains of modern specimens. The subfossil sites found around most of the island demonstrate that most giant lemurs had wide distributions and that ranges of living species have contracted significantly since the arrival of humans.
Lemurs were first classified in 1758 by Carl Linnaeus, and the taxonomy remains controversial today, with approximately 70 to 100 species and subspecies recognized, depending on how the term "species" is defined. Having undergone their own independent evolution on Madagascar, lemurs have diversified to fill many ecological niches normally filled by other types of mammals. They include the smallest primates in the world, and once included some of the largest. Since the arrival of humans approximately 2,000 years ago, lemurs have become restricted to 10% of the island, or approximately 60,000 square kilometers (23,000 sq mi), and many face extinction. Concerns over lemur conservation have affected lemur taxonomy, since distinct species receive increased conservation attention compared to subspecies.
Charles Lamberton was a French paleontologist who lived and studied on the island of Madagascar between 1911 and 1948 and specialized in the recently extinct subfossil lemurs. He made significant contributions towards fixing misattributions of skeletal remains and poor interpretations of subfossil lemur behavior. His paleontological expeditions during the 1930s led to the discovery of a new species of Mesopropithecus, a type of sloth lemur. Three species—one mammal and two reptiles—were named after him, although one is now considered a taxonomic synonym.
Berthe Rakotosamimanana was a primatologist and palaeontologist from Madagascar.
Ampasambazimba is a mountain peak and subfossil site in Madagascar, near Analavory, (Itasy) most known for being the site of the remains of the extinct giant sloth lemur Archaeoindris.
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