''Oreopithecus'' (from the Greek , and , , meaning "hill-ape") is an extinct genus of

hominoid Apes (collectively Hominoidea ) are a clade of Old World simians native to sub-Saharan Africa and Southeast Asia (though they were more widespread in Africa, most of Asia, and as well as Europe in prehistory), which together with its sister g ...

primate Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians ( monkeys and apes, the latter including ...

from the

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

epoch whose

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s have been found in today's

Tuscany it, Toscano (man) it, Toscana (woman) , population_note = , population_blank1_title = , population_blank1 = , demographics_type1 = Citizenship , demographics1_footnotes = , demographics1_title1 = Italian , demogra ...

and

Sardinia Sardinia ( ; it, Sardegna, label=Italian, Corsican and Tabarchino ; sc, Sardigna , sdc, Sardhigna; french: Sardaigne; sdn, Saldigna; ca, Sardenya, label=Algherese and Catalan) is the second-largest island in the Mediterranean Sea, after ...

Italy Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical ...

. It existed nine to seven million years ago in the Tusco-Sardinian area when this region was an isolated island in a chain of islands stretching from central Europe to northern Africa in what was becoming the

Mediterranean Sea The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ...

. ''Oreopithecus'' was one of many European immigrants that settled this area in the

Vallesian The Vallesian age is a period of geologic time (11.6–9.0 Ma) within the Miocene used more specifically with European Land Mammal Ages. It precedes the Turolian age and follows the Astaracian age. The so-called Vallesian Crisis resulted in the ...

–

Turolian The Turolian age is a period of geologic time (9.0–5.3 Ma) within the Miocene used more specifically with European Land Mammal Ages. It precedes the Ruscinian age and follows the Vallesian age. The Turolian overlaps the Tortonian The Tort ...

transition and one of few hominoids, together with ''

Sivapithecus ''Sivapithecus'' () (syn: ''Ramapithecus)'' is a genus of extinct apes. Fossil remains of animals now assigned to this genus, dated from 12.2 million years old in the Miocene, have been found since the 19th century in the Siwalik Hills of the I ...

'' in Asia, to survive the so-called

Vallesian Crisis The Vallesian age is a period of geologic time (11.6–9.0 Ma) within the Miocene used more specifically with European Land Mammal Ages. It precedes the Turolian age and follows the Astaracian age. The so-called Vallesian Crisis resulted in the e ...

. To date, dozens of individuals have been discovered at the Tuscan localities of

Montebamboli Montebamboli is a hamlet and località in the comune of Massa Marittima, Tuscany, Italy. The settlement was first mentioned in a parchment from the year 754, and it is located in the hills of what is now the centre of Massa Marittima, within the P ...

Montemassi Montemassi is a village in Tuscany, central Italy, administratively part of the ''comune'' of Roccastrada, in the province of Grosseto. It is located on a hill about above sea level. The village originated as a fortified village of the Aldobrande ...

, Casteani,

Ribolla Ribolla is a village in southern Tuscany, a ''frazione'' of the ''comune'' of Roccastrada, in the province of Grosseto. At the time of the 2001 census its population amounted to .Baccinello Basin, making it one of the best-represented fossil

ape Apes (collectively Hominoidea ) are a clade of Old World simians native to sub-Saharan Africa and Southeast Asia (though they were more widespread in Africa, most of Asia, and as well as Europe in prehistory), which together with its sister g ...

Evolutionary history

''Oreopithecus bambolii'' was first described by French paleontologist

Paul Gervais Paul Gervais full name François Louis Paul Gervais (26 September 1816 – 10 February 1879) was a French palaeontologist and entomologist. Biography Gervais was born in Paris, where he obtained the diplomas of doctor of science and of medicine ...

in 1872, after the discovery of a juvenile mandible by Professor

Igino Cocchi Igino Cocchi (27 October 1827 – 18 August 1913) was an Italian geologist and paleontologist who worked at the Museum of Natural History, Florence. Cicchi was born in Terrarossa, Val di Magra where and studied Latin and natural sciences, graduat ...

in a lignite mine at Montebamboli in 1862. In 1890, nearly a dozen new specimens were reported by Guiseppe Ristori, among them an upper jaw. In 1898, a left lower jaw was described by Felice Ottolenghi. In 1907, Giuseppe Merciai reported four maxillae and a lower jaw from the Grosseto mine at Ribolla. During this period there was no consensus whether ''Oreopithecus'' was a monkey or an ape. From 1949 onwards, Swiss paleontologist began to restudy the known material. In 1954, 1955, 1956 and 1958 he claimed ''Oreopithecus'' were a true hominin—based on its premolars, short jaws and reduced

canines Canine may refer to: Zoology and anatomy * a dog-like Canid animal in the subfamily Caninae ** ''Canis'', a genus including dogs, wolves, coyotes, and jackals ** Dog, the domestic dog * Canine tooth, in mammalian oral anatomy People with the surn ...

, at the time considered diagnostic of the hominin family. This hypothesis was immediately hotly discussed by his fellow palaeontologists. When he toured the world to give a series of lectures, his views generated an enormous press coverage, often being presented as a challenge to the Darwinian descent of man from apes. After Hürzeler was invited to give a lecture in New York in March 1956, the

Wenner-Gren Foundation Axel Lennart Wenner-Gren (5 June 1881 – 24 November 1961) was a Swedish entrepreneur and one of the wealthiest men in the world during the 1930s. Early life He was born on 5 June 1881 in Uddevalla, a town on the west coast of Sweden. He w ...

decided to finance excavations in Italy, with the cooperation of the Italian paleontologist

Alberto Carlo Blanc Alberto Carlo Blanc (30 July 1906 – 3 July 1960, Rome) was an Italian paleontologist who studied human evolution. He was a professor at the University of Pisa, Rome and is best known for the discovery of the Circeo neanderthal skull in February 1 ...

. On 2 August 1958, Hürzeler's views seemed to be confirmed when he discovered a complete skeleton in

Baccinello Baccinello is a village in Tuscany, central Italy, administratively a frazione of the comune of Scansano, province of Grosseto. At the time of the 2001 census its population amounted to 284.biped Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning 'two feet' (from Latin ''bis'' 'double' ...

because of the short pelvis was closer to those of hominins than those of chimpanzees and

gorilla Gorillas are herbivorous, predominantly ground-dwelling great apes that inhabit the tropical forests of equatorial Africa. The genus ''Gorilla'' is divided into two species: the eastern gorilla and the western gorilla, and either four or fi ...

s. Hominin affinities claimed for ''Oreopithecus'' remained controversial for decades until new analyses in the 1990s reasserted that ''Oreopithecus'' was directly related to ''

Dryopithecus ''Dryopithecus'' is a genus of extinct great apes from the middle– late Miocene boundary of Europe 12.5 to 11.1 million years ago (mya). Since its discovery in 1856, the genus has been subject to taxonomic turmoil, with numerous new specie ...

''. The peculiar cranial and dental features were explained as consequences of insular isolation. This new evidence confirmed that ''Oreopithecus'' was bipedal but also revealed that its peculiar form of bipedalism was much different from that of ''

Australopithecus ''Australopithecus'' (, ; ) is a genus of early hominins that existed in Africa during the Late Pliocene and Early Pleistocene. The genus ''Homo'' (which includes modern humans) emerged within ''Australopithecus'', as sister to e.g. ''Austral ...

''. The

hallux Toes are the digits (fingers) of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being '' digitigrade''. Humans, and other animals that walk on the soles of their feet, are described as being '' pl ...

formed a 100° angle with the other toes, which enabled the foot to act as a tripod in erect posture, but prevented ''Oreopithecus'' from developing a fast bipedal stride. When a land bridge broke the isolation of the Tusco-Sardinian area , large predators such as ''

Machairodus ''Machairodus'' (from el, μαχαίρα , 'knife' and el, ὀδούς 'tooth') is a genus of large machairodontine saber-toothed cats that lived in Africa, Eurasia and North America during the late Miocene. It is the animal from which the su ...

'' and ''

Metailurus ''Metailurus'' is a genus of saber-toothed cat in the family Felidae, and belonging to the tribe Metailurini, which occurred in North America, Eurasia and Africa from the Miocene to the Middle Pleistocene. This genus was formally described by O. ...

'' were present among the new generation of European immigrants and ''Oreopithecus'' faced quick extinction together with other endemic genera.

Taxonomic classification

Known as the "enigmatic

", ''Oreopithecus'' can dramatically rewrite the palaeontological map depending on whether it is a descendant of the European ape ''

'' or an African

anthropoid Anthropoid means 'ape/human feature' and may refer to: * Simian, monkeys and apes (anthropoids, or suborder Anthropoidea, in earlier classifications) *Anthropoid apes - apes that are closely related to humans (e.g., former family Pongidae and some ...

. Some have suggested the unique locomotory behavior of ''Oreopithecus'' requires a revision of the current consensus on the timing of bipedality in human developmental history, but there is limited agreement on this point among

paleontologist Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...

s. Simons (1960) considered ''Oreopithecus'' closely related to the early Oligocene ''

Apidium The genus ''Apidium'' (from Latin, a diminutive of the Egyptian bull god, Apis, as the first fossils were thought to be from a type of a cow) is that of at least three extinct primates living in the early Oligocene, from 30 to 28 million years ...

'', a small arboreal anthropoid that lived nearly 34 million years ago in Egypt. ''Oreopithecus'' shows strong links to modern apes in its

postcranium Postcrania (postcranium, adjective: postcranial) in zoology and vertebrate paleontology is all or part of the skeleton apart from the skull. Frequently, fossil remains, e.g. of dinosaurs or other extinct tetrapods, consist of partial or isolated s ...

and, in this respect, it is the most modern Miocene ape below the neck, with closest similarities to the postcranial elements of ''

'', but its dentition is adapted to a leafy diet and a close link is uncertain. Others claim it to be either the sister taxon to

Cercopithecoidea Old World monkey is the common English name for a family of primates known taxonomically as the Cercopithecidae (). Twenty-four genera and 138 species are recognized, making it the largest primate family. Old World monkey genera include baboons ...

or an even direct human ancestor, but it is usually placed in its own subfamily within Hominidae. It could instead be added to the same subfamily as ''Dryopithecus'', perhaps as a distinct tribe (Oreopithecini). A cladistic analysis of ''Nyanzapithecus alesi'' recovers ''Oreopithecus'' as a member of the proconsulid subfamily Nyanzapithecinae.

Physical characteristics

''Oreopithecus bambolii'' is estimated to have weighed . It possessed a relatively short snout, elevated nasal bones, small and globular

neurocranium In human anatomy, the neurocranium, also known as the braincase, brainpan, or brain-pan is the upper and back part of the skull, which forms a protective case around the brain. In the human skull, the neurocranium includes the calvaria or skul ...

, vertical

orbital plane The orbital plane of a revolving body is the geometric plane in which its orbit lies. Three non-collinear points in space suffice to determine an orbital plane. A common example would be the positions of the centers of a massive body (host) an ...

, and gracile facial bones. The shearing crests on its

molars The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name ''molar'' derives from Latin, ''molaris dens'', meaning "millstone to ...

suggest a diet specializing in plant leaves. The very robust lower face, with a large attachment surface for the

masseter muscle In human anatomy, the masseter is one of the muscles of mastication. Found only in mammals, it is particularly powerful in herbivores to facilitate chewing of plant matter. The most obvious muscle of mastication is the masseter muscle, since it ...

and a sagittal crest for attachment of the

temporal muscle In anatomy, the temporalis muscle, also known as the temporal muscle, is one of the muscles of mastication (chewing). It is a broad, fan-shaped convergent muscle on each side of the head that fills the temporal fossa, superior to the zygomat ...

, indicates a heavy

masticatory Chewing or mastication is the process by which food is crushed and ground by teeth. It is the first step of digestion, and it increases the surface area of foods to allow a more efficient break down by enzymes. During the mastication process, t ...

apparatus. Its teeth were small relative to body size. The lack of a diastema (gap) between the second

incisor Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wher ...

and first premolar of the

mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

indicates that ''Oreopithecus'' had

of size comparable to the rest of its dentition. In many primates, small canines correlate with reduced inter-male competition for access to mates and less

sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most an ...

Positional behavior

Its habitat appears to have been swampy, and not

savanna A savanna or savannah is a mixed woodland- grassland (i.e. grassy woodland) ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to ...

forest A forest is an area of land dominated by trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, and ecological function. The United Nations' ...

. The postcranial anatomy of ''Oreopithecus'' features adaptations for suspensory arborealism. Functional traits related to suspensory locomotion include its broad thorax, short trunk, high

intermembral index The intermembral index is a ratio used to compare limb proportions, expressed as a percentage. It is equal to the length of forelimbs (humerus plus radius) divided by the length of the hind limbs (femur plus tibia) multiplied by 100, otherwise writ ...

, long and slender digits, and extensive mobility in virtually all joints. Its fingers and arms seem to show adaptations for climbing and swinging. Its foot has been described as chimp-like, but is different from those of extant primates. The habitual line of leverage of the primate foot is parallel to the third

metatarsal bone The metatarsal bones, or metatarsus, are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the ...

. In ''Oreopithecus'', the

lateral Lateral is a geometric term of location which may refer to: Healthcare *Lateral (anatomy), an anatomical direction * Lateral cricoarytenoid muscle * Lateral release (surgery), a surgical procedure on the side of a kneecap Phonetics *Lateral co ...

metatarsals are permanently abducted so that this line falls between the first and second metatarsals instead. Furthermore, the shape of the tarsus indicate loads on the foot were transmitted to the medial side of the foot instead of the lateral, like in other primates. The metatarsals are short and straight, but have a lateral orientation increase. Its foot proportions are close to the unusual proportions of ''Gorilla'' and ''Homo'' but are distinct from those found in specialized climbers. The lack of predators and the limitation of space and resources in ''Oreopithecus''′ insular environment favored a locomotor system optimized for low energy expenditure rather than speed and mobility. ''Oreopithecus'' has been claimed to exhibit features that are adaptations to upright walking, such as the presence of a lumbar curve, in distinction to otherwise similar species known from the same period. Since the fossils have been dated to about 8

million years ago The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds. Usage Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (million years ago) ...

, this would represent an unusually early appearance of upright posture. However, a reevaluation of the spine from a skeleton of ''Oreopithecus'' has led to the conclusion that it lacked adaptations for habitual

biped Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning 'two feet' (from Latin ''bis'' 'double' ...

ality

Semicircular canals

The

semicircular canal In mathematics (and more specifically geometry), a semicircle is a one-dimensional locus of points that forms half of a circle. The full arc of a semicircle always measures 180° (equivalently, radians, or a half-turn). It has only one line o ...

s of the inner ear serves as a sense organ for balance and controls the reflex for gaze stabilization. The inner ear has three canals on each side of the head, and each of the six canals encloses a membranous duct that forms an

endolymph Endolymph is the fluid contained in the membranous labyrinth of the inner ear. The major cation in endolymph is potassium, with the values of sodium and potassium concentration in the endolymph being 0.91 mM and 154 mM, respectively. I ...

-filled circuit. Hair cells in the duct's auditory ampulla pick up endolymph disturbances caused by movement, which register as rotatory head movement. They respond to body sway of frequencies greater than 0.1 Hz and trigger the vestibulocollic (neck) reflex and vestibuloocular (eye) reflex to recover balance and gaze stability. The bony semicircular canals allow estimates of duct arc length and orientation with respect to the sagittal plane. Across species, the semicircular canals of agile animals have larger arcs than those of slower ones. For example, the rapid leaper ''

Tarsius bancanus Horsfield's tarsier (''Cephalopachus bancanus''), also known as the western tarsier, is the only species of tarsier in the genus ''Cephalopachus''. Named for American naturalist Thomas Horsfield, it occurs on Borneo, Sumatra and nearby islands a ...

'' has semicircular canals much bigger than the slow-climbing ''

Nycticebus coucang The Sunda slow loris (''Nycticebus coucang'') or greater slow loris is a strepsirrhine primate and a species of slow loris native to Indonesia, West Malaysia, southern Thailand and Singapore. It measures from head to tail and weighs between . ...

''. The semicircular canals of brachiating gibbons are bigger than those of arboreal and terrestrial quadrupedal

great ape The Hominidae (), whose members are known as the great apes or hominids (), are a taxonomic family of primates that includes eight extant species in four genera: '' Pongo'' (the Bornean, Sumatran and Tapanuli orangutan); ''Gorilla'' (the ...

s. As a rule of thumb, arc size of the ducts ''decreases'' with body mass and consequently slower angular head motions. Arc size ''increases'' with greater agility and thus more rapid head motions. Modern

human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, cultu ...

s have bigger arcs on their anterior and posterior canals, which reflect greater angular motion along the sagittal plane. The lateral canal has a smaller arc size, corresponding to reduced head movement from side to side.

Allometric Allometry is the study of the relationship of body size to shape, anatomy, physiology and finally behaviour, first outlined by Otto Snell in 1892, by D'Arcy Thompson in 1917 in ''On Growth and Form'' and by Julian Huxley in 1932. Overview Allome ...

measurements on the

bony labyrinth The bony labyrinth (also osseous labyrinth or otic capsule) is the rigid, bony outer wall of the inner ear in the temporal bone. It consists of three parts: the vestibule, semicircular canals, and cochlea. These are cavities hollowed out of the su ...

of BAC-208, a fragmentary cranium that preserves a complete, undeformed

petrosal bone The petrous part of the temporal bone is pyramid-shaped and is wedged in at the base of the skull between the sphenoid and occipital bones. Directed medially, forward, and a little upward, it presents a base, an apex, three surfaces, and three an ...

suggest that ''Oreopithecus'' moved with agility comparable to extant

great apes The Hominidae (), whose members are known as the great apes or hominids (), are a taxonomic family of primates that includes eight extant species in four genera: '' Pongo'' (the Bornean, Sumatran and Tapanuli orangutan); ''Gorilla'' (the ...

. Its anterior and lateral semicircular canal sizes fall within the range for great apes. Its relatively large posterior arc implies that ''Oreopithecus'' was more proficient at stabilizing angular head motion along the sagittal plane.

Dexterity

''Oreopithecus'' had hominin-like hand proportions that allowed a firm, pad-to-pad precision grip. Features present in the hands of neither non-human-extant nor fossil apes include hand length, relative thumb length, a deep and large insertion for the

flexor pollicis longus The flexor pollicis longus (; FPL, Latin ''flexor'', bender; ''pollicis'', of the thumb; ''longus'', long) is a muscle in the forearm and hand that flexes the thumb. It lies in the same plane as the flexor digitorum profundus. This muscle is un ...

, and the shape of the

carpometacarpal joint The carpometacarpal (CMC) joints are five joints in the wrist that articulate the distal row of carpal bones and the proximal bases of the five metacarpal bones. The CMC joint of the thumb or the first CMC joint, also known as the trapeziometaca ...

between the metacarpal bone of the index finger and the

capitate bone The capitate bone is a bone in the human wrist found in the center of the carpal bone region, located at the distal end of the radius and ulna bones. It articulates with the third metacarpal bone (the middle finger) and forms the third carpomet ...

. At the base of the

second metacarpal bone The second metacarpal bone (metacarpal bone of the index finger) is the longest, and its base the largest, of all the metacarpal bones.''Gray's Anatomy'' (1918). See infobox. Human anatomy Its base is prolonged upward and medialward, forming a ...

, the facet for the

capitate The capitate bone is a bone in the human wrist found in the center of the carpal bone region, located at the distal end of the radius and ulna bones. It articulates with the third metacarpal bone (the middle finger) and forms the third carpomet ...

is oriented transversally, as in hominins. The capitate, on the other hand, lacks the waisting associated with apes and climbing, and still present in ''

''. ''Oreopithecus'' share the specialised orientation at the carpometacarpal joint with '' A. afarenis'' and the marked groove for the flexor pollicis longus with '' A. africanus''. It is thus likely that the hand morphology of ''Oreopithecus'' is

derived Derive may refer to: * Derive (computer algebra system), a commercial system made by Texas Instruments * ''Dérive'' (magazine), an Austrian science magazine on urbanism *Dérive, a psychogeographical concept See also * *Derivation (disambiguatio ...

for apes and convergent for early hominins.

Explanations

Notes

References

* * * * * * * * * * *

External links

* — A photo of an ''Oreopithecus bamboli'' jaw * {{Taxonbar, from=Q131700 Miocene primates of Europe Prehistoric apes Fossil taxa described in 1872 Prehistoric mammals of Europe Prehistoric primate genera