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Simian Shelf
The simian shelf is a bony thickening on the front of the ape mandible. Its function is to reinforce the jaw, though it also has the effect of considerably reducing the movement of the tongue by restricting the area available for muscles. Humans are the only primates to have protruding chins, though some fossils of early humans show evidence of a simian shelf. Evolution of the simian shelf In Maboko Island (1988), the lower jaw of a Kenyapithecus was found, and it provides signs of the simian shelf evolution in modern apes. Where the simian shelf is present, the bottom teeth will be leaning forward. This happened to be a unique feature of the Kenyapithecus leading there to be a link between the two. This sign of evolution was identified as shown through the lower incisors that lean forward and are known to be used to break hard objects. The lower incisors were concluded to be an adaptive feature as it was an adaptation for "hard object feeding including... large mandible... and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mandible
In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone is the skull's only movable, posable bone, sharing Temporomandibular joint, joints with the cranium's temporal bones. The mandible hosts the lower Human tooth, teeth (their depth delineated by the alveolar process). Many muscles attach to the bone, which also hosts nerves (some connecting to the teeth) and blood vessels. Amongst other functions, the jawbone is essential for chewing food. Owing to the Neolithic Revolution, Neolithic advent of agriculture (), human jaws evolved to be Human jaw shrinkage, smaller. Although it is the strongest bone of the facial skeleton, the mandible tends to deform in old age; it is also subject to Mandibular fracture, fracturing. Surgery allows for the removal of jawbone fragments (or its entirety) as well a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Human
Humans (''Homo sapiens'') or modern humans are the most common and widespread species of primate, and the last surviving species of the genus ''Homo''. They are Hominidae, great apes characterized by their Prehistory of nakedness and clothing#Evolution of hairlessness, hairlessness, bipedality, bipedalism, and high Human intelligence, intelligence. Humans have large Human brain, brains, enabling more advanced cognitive skills that facilitate successful adaptation to varied environments, development of sophisticated tools, and formation of complex social structures and civilizations. Humans are Sociality, highly social, with individual humans tending to belong to a Level of analysis, multi-layered network of distinct social groups — from families and peer groups to corporations and State (polity), political states. As such, social interactions between humans have established a wide variety of Value theory, values, norm (sociology), social norms, languages, and traditions (co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chin
The chin is the forward pointed part of the anterior mandible (List_of_human_anatomical_regions#Regions, mental region) below the lower lip. A fully developed human skull has a chin of between 0.7 cm and 1.1 cm. Evolution The presence of a well-developed chin is considered to be one of the morphological characteristics of ''Homo sapiens'' that Neanderthal anatomy#Distinguishing physical traits, differentiates them from other human ancestors such as the closely related Neanderthal, Neanderthals. Early human ancestors have varied Mandibular symphysis, symphysial morphology, but none of them have a well-developed chin. The origin of the chin is traditionally associated with the anterior–posterior breadth shortening of the dental arch or tooth row; however, its general mechanical or functional advantage during feeding, developmental origin, and link with human speech, physiology, and social influence are highly debated. Functional perspectives Robinson (1913) suggests that the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maboko Island
Maboko Island is a small island lying in the Winam Gulf of Lake Victoria, in Nyanza Province of western Kenya. It is about 1.8 km long by 1 km wide. It is an important Middle Miocene, Middle Miocene Paleontology, paleontological site with fossiliferous deposits that were discovered in the 1930s. The age of the deposits is estimated to be , and they are especially important for the abundance of primate fossils they contain. Excavations Miocene fossils in the fluvial deposits of Maboko was first discovered by Walter Edwin Owen, Archdeacon W.E. Owen in 1933, who started an excavation later that year which yielded a lot of vertebrate fossils. Owen's excavations continued the following two years supervised by Donald Gordon MacInnes. Then few expeditions visited the island before MacInnes returned together with Louis Leakey in 1947. These excavations resulted in a large number of craniodental (crania and teeth) remains of a medium seized cercopithecoid monkey and cranial and postcr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kenyapithecus
''Kenyapithecus wickeri'' is a fossil ape discovered by Louis Leakey in 1961 at a site called Fort Ternan in Kenya. The upper jaw and teeth were dated to 14 million years ago. One theory states that ''Kenyapithecus'' may be the common ancestor of all the great apes. More recent investigations suggest ''Kenyapithecus'' is more primitive than that and is only slightly more modern than ''Proconsul'', which is considered to be an ape. Evidence suggests that ''Kenyapithecus wickeri'' was one of the species that started a radiation of apes out of Africa. Morphology Impressed by ''Kenyapithecus''s modern-looking teeth, Leakey declared ''Kenyapithecus'' to be "a very early ancestor of man himself." ''Kenyapithecus'' possessed craniodental adaptations for hard object feeding including thicker molar enamel, and a large mandible, large premolars and upper incisors that are similar to those seen in living pitheciine monkeys. ''Kenyapithecus'' also possessed macaque-like limbs adap ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genus
Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In binomial nomenclature, the genus name forms the first part of the binomial species name for each species within the genus. :E.g. ''Panthera leo'' (lion) and ''Panthera onca'' (jaguar) are two species within the genus ''Panthera''. ''Panthera'' is a genus within the family Felidae. The composition of a genus is determined by taxonomy (biology), taxonomists. The standards for genus classification are not strictly codified, so different authorities often produce different classifications for genera. There are some general practices used, however, including the idea that a newly defined genus should fulfill these three criteria to be descriptively useful: # monophyly – all descendants of an ancestral taxon are grouped together (i.e. Phylogeneti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mandibular Symphysis
In human anatomy, the facial skeleton of the skull the external surface of the mandible is marked in the median line by a faint ridge, indicating the mandibular symphysis (Latin: ''symphysis menti'') or line of junction where the two lateral halves of the mandible typically fuse in the first year of life (6–9 months after birth). It is not a true symphysis as there is no cartilage between the two sides of the mandible. This ridge divides below and encloses a triangular eminence, the mental protuberance, the base of which is depressed in the center but raised on either side to form the mental tubercle. The lowest (most inferior) end of the mandibular symphysis — the point of the chin — is called the "menton". It serves as the origin for the geniohyoid and the genioglossus muscles. Other animals Solitary mammalian carnivores that rely on a powerful canine bite to subdue their prey have a strong mandibular symphysis, while pack hunters delivering shallow bites have a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Suprahyoid Muscles
The suprahyoid muscles are four muscles located above the hyoid bone in the neck. They are the digastric, stylohyoid, geniohyoid, and mylohyoid muscles. They are all pharyngeal muscles, with the exception of the geniohyoid muscle. The digastric is uniquely named for its two bellies. Its posterior belly rises from the mastoid process of the cranium and slopes downward and forward. The anterior belly arises from the digastric fossa on the inner surface of the mandibular body, which slopes downward and backward. The two bellies connect at the intermediate tendon. The intermediate tendon passes through a connective tissue loop attached to the hyoid bone. The mylohyoid muscles are thin, flat muscles that form a sling inferior to the tongue supporting the floor of the mouth. The geniohyoids are short, narrow muscles that contact each other in the midline. The stylohyoids are long, thin muscles that are nearly parallel with the posterior belly of the digastric muscle. Function ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Primate Anatomy
Primates is an order of mammals, which is further divided into the strepsirrhines, which include lemurs, galagos, and lorisids; and the haplorhines, which include tarsiers and simians (monkeys and apes). Primates arose 74–63 million years ago first from small terrestrial mammals, which adapted for life in tropical forests: many primate characteristics represent adaptations to the challenging environment among tree tops, including large brain sizes, binocular vision, color vision, vocalizations, shoulder girdles allowing a large degree of movement in the upper limbs, and opposable thumbs (in most but not all) that enable better grasping and dexterity. Primates range in size from Madame Berthe's mouse lemur, which weighs , to the eastern gorilla, weighing over . There are 376–524 species of living primates, depending on which classification is used. New primate species continue to be discovered: over 25 species were described in the 2000s, 36 in the 2010s, and six in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
