page_title: Lemur
section_title: Anatomy and physiology
hierarchical_section_title: Lemur / Anatomy and physiology
caption_attribution_description: English: Varecia variegata foot, showing toilet-claw (2nd toe) and nails (all other toes); taken during a routine physical examination
context_page_description: Lemurs are mammals of the order Primates, divided into 8 families and consisting of 15 genera and around 100 existing species. They are native only to the island of Madagascar. Most existing lemurs are small, have a pointed snout, large eyes, and a long tail. They chiefly live in trees, and are active at night.
  Lemurs share resemblance with other primates, but evolved independently from monkeys and apes. Due to Madagascar's highly seasonal climate, lemur evolution has produced a level of species diversity rivaling that of any other primate group. Until shortly after humans arrived on the island around 2,000 years ago, there were lemurs as large as a male gorilla. Most species have been discovered or promoted to full species status since the 1990s; however, lemur taxonomic classification is controversial and depends on which species concept is used.
  Lemurs range in weight from the 30-gram mouse lemur to the 9-kilogram indri. Lemurs share many common basal primate traits, such as divergent digits on their hands and feet, and nails instead of claws. However, their brain-to-body size ratio is smaller than that of anthropoid primates.
context_section_description: Lemurs vary greatly in size. They include the smallest primates in the world and, until recently, also included some of the largest. They currently range in size from about 30 g (1.1 oz) for Madame Berthe's mouse lemur (Microcebus berthae) up to 7–9 kg (15–20 lb) for the indri (Indri indri) and diademed sifaka (Propithecus diadema). One recently extinct species rivaled the gorilla in size, at 160–200 kg (350–440 lb) for Archaeoindris fontoynonti.
  Like all primates, lemurs have five divergent digits with nails (in most cases) on their hands and feet. Most lemurs possess a laterally compressed, elongated nail, called a toilet-claw, on the second toe and use it for scratching and grooming. In addition to the toilet-claw, lemurs share a variety of other traits with other strepsirrhine primates, which include a rhinarium (or "wet nose"); a fully functional vomeronasal organ, which detects pheromones; a postorbital bar and the lack of postorbital closure (a wall of thin bone behind the eye); orbits (bony sockets that enclose the eye) that are not fully facing forward; left and right mandible (lower jaw) bones that are not fully fused; and a small brain-to-body mass ratio.
  Additional traits shared with other prosimian primates (strepsirrhine primates and tarsiers) include a bicornuate (two-horned) uterus and epitheliochorial placentation. Because their thumbs are only pseudo-opposable, making their movement less independent of the other fingers, their hands are less than perfect at grasping and manipulating objects. On their feet, they have a widely abducted hallux (first toe) which facilitates the grasping of tree limbs. A common misconception is that lemurs have a prehensile tail, a trait found only in New World monkeys, particularly atelids, among primates. Lemurs also rely heavily on their sense of smell, a trait shared with most other mammals and early primates, but not with the visually oriented higher primates. This sense of smell is important in terms of marking territory as well as provide an indication of whether or not another lemur is a viable breeding partner.
  Lemurs are a diverse group of primates in terms of morphology and physiology. Some lemurs, such as the sportive lemurs and indriids, have longer hind limbs than forelimbs, making them excellent leapers. Indriids also have a specialized digestive system for folivory, exhibiting enlarged salivary glands, a spacious stomach, and an elongated caecum (lower gut) that facilitates fermentation. The hairy-eared dwarf lemur (Allocebus trichotis) reportedly has a very long tongue, allowing it to feed on nectar. Likewise, the red-bellied lemur (Eulemur rubriventer) has a feathery brush-shaped tongue, also uniquely adapted to feed on nectar and pollen. The aye-aye has evolved some traits that are unique among primates, making it stand out among the lemurs. Such traits include continuously growing, rodent-like front teeth for gnawing through wood and hard seeds; a highly mobile, filiform (filament-shaped) middle finger for extracting food from tiny holes; large, bat-like ears for detecting hollow spaces within trees; and use of self-generated acoustical cues to forage.
  Lemurs are unusual since they have great variability in their social structure, yet generally lack sexual dimorphism in size and canine tooth morphology. However, some species tend towards having larger females, and two species of true lemur (genus Eulemur), the gray-headed lemur (E. albocollaris) and the red lemur (E. rufus), exhibit size differences in canine teeth. True lemurs show sexual dichromatism (sexual differences in fur coloration), but the difference between the genders varies from strikingly obvious, as in the blue-eyed black lemur (E. macaco), to nearly imperceptible in the case of the common brown lemur (E. fulvus).
  Crypsis, or the inability of humans to visually distinguish between two or more distinct species, has recently been discovered among lemurs, particularly within the sportive lemurs (Lepilemur) and mouse lemurs (Microcebus). With sportive lemurs, subspecies were traditionally defin
caption: Close-up of a ruffed lemur's foot, showing the toilet-claw on the second toe and nails on all other toes
exif: {"Image Make": "Canon", "Image Model": "Canon PowerShot SD800 IS", "Image Orientation": "Horizontal (normal)", "Image XResolution": "180", "Image YResolution": "180", "Image ResolutionUnit": "Pixels/Inch", "Image DateTime": "2008:09:26 11:51:14", "Image YCbCrPositioning": "Centered", "Image Software": "Adobe Photoshop CS Windows", "Image ExifOffset": "324", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "1234", "Thumbnail JPEGInterchangeFormatLength": "4966", "EXIF ExposureTime": "1/15", "EXIF FNumber": "14/5", "EXIF ExifVersion": "0220", "EXIF DateTimeOriginal": "2008:09:16 10:37:59", "EXIF DateTimeDigitized": "2008:09:16 10:37:59", "EXIF ComponentsConfiguration": "YCbCr", "EXIF CompressedBitsPerPixel": "5", "EXIF ShutterSpeedValue": "125/32", "EXIF ApertureValue": "95/32", "EXIF ExposureBiasValue": "0", "EXIF MaxApertureValue": "95/32", "EXIF MeteringMode": "Pattern", "EXIF Flash": "Flash did not fire, compulsory flash mode", "EXIF FocalLength": "23/5", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "2532", "EXIF ExifImageLength": "2232", "Interoperability InteroperabilityIndex": "R98", "Interoperability InteroperabilityVersion": "[48, 49, 48, 48]", "Interoperability RelatedImageWidth": "3072", "Interoperability RelatedImageLength": "2304", "EXIF InteroperabilityOffset": "1084", "EXIF FocalPlaneXResolution": "20480", "EXIF FocalPlaneYResolution": "3456000/169", "EXIF FocalPlaneResolutionUnit": "2", "EXIF SensingMethod": "One-chip color area", "EXIF FileSource": "Digital Camera", "EXIF CustomRendered": "Normal", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Auto", "EXIF DigitalZoomRatio": "3/2", "EXIF SceneCaptureType": "Standard"}