Primate Definitions

These are selected primate evolution definitions. Click on the letters below to move through the page more quickly.

[A] [B] [C] [D] [E] [F] [G] [H] [I] [J] [K] [L] [M] [N] [O] [P] [Q] [R] [S] [T] [V] [Z]

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abduction: "movement of a limb or part of a limb away from the midline of the body." &

adduction: "movement of a limb toward the midline of the body." &

allometry: "study of the relative growth relationships between different parts of an organism; mathematically expressed by the allometric equation Y=aXb where Y and X are the two variables under consideration." &

allopatric speciation: "emergence of new species from populations that are geographically separated from each other." &

alveolar process: "the tooth-bearing portion of the jaws." &

analogous: "describes the similarity of form or structure between two species that they do not share with their nearest common ancestor; that is, the similar structure has evolved independently in the two species and is due to convergent evolution." &

antemolar dentition: "all the teeth mesial to (forward of) the molars; incisors, canines, and premolars." &

anterocone: "small cusp on the front of the incisors in some plesiadapiforms." &

arboreal: "living mainly in trees." &

arboreal quadrupeds: "animals that use all four limbs in walking and running on tree limbs." &

articulation: "a joint between two or more bones." &

ascending mandibular ramus: "vertical portion of the mandible; also called the vertical ramus of the mandible." &

astragalus: "ankle bone; also called the talus." &

auditory bulla: "bone surrounding the middle-ear cavity; formed by the petrosal bone in primates." &

auditory meatus: "external opening of the ear canal. Also called the external auditory tube." &

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basicranium: "base of the skull, formed mainly by the occipital and sphenoid bones." &

Bergmann's rule: "general rule in zoology that animals living in cold climates tend to be larger than closely related species living in warm climates in order to lower their surface-area-to-volume ratio and thus reduce heat loss." &

bilophodont: "refers to a type of molar construction in which there are two parallel enamel ridges running from the protocone and paracone anteriorly and the hypocone and metacone posteriorly on the upper molars and from the protoconid and metaconid anteriorly and the hypoconid and entoconid posteriorly on the lower molars; typical in Old World monkeys." &

binocular vision: "vision in which both visual axes can focus on a distant object to produce a stereoscopic (three-dimensional) image." &

brachiation: "arboreal locomotion in which the animal progresses below branches by using only the forelimbs." &

buccal: "toward the lateral (cheek) side of a tooth." &

bunodont: "refers to teeth with low, rounded cusps." &

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calcaneus: "heel bone." &

calvaria: "top of the skull; the skullcap." &

canine fossa: "depression or slight concavity in the alveolar process of the maxilla just behind the canine jugum." &

canine jugum: "vertical ridge in the alveolar process of the maxilla caused by an enlarged canine root." &

caniniform: "shaped like a canine." &

capitulum: "small, rounded head on the lateral articular surface of the distal humerus that articulates with the radius." &

carnivorous: "meat eating." &

carnivore: "animals whose primary or sole source of food is meat." &

cathemeral: "active intermittenly throughout the twenty-four-hour day rather than active only during the day (diurnal) or only during the night (nocturnal)." &

cecum: "a blind pouch at the junction of the small and large intestine." &

central sulcus: "transverse groove across the top of the cerebral cortex separating the somatic sensory area from the somatic motor area." &

cingulum: "shelf of enamel running around the periphery of a tooth." &

clavicle: "collarbone." &

conspecific: "of the same species." &

coronoid process: "part of the ascending mandibular ramus of the mandible where the temporalis muscle attaches." &

coronolateral sulcus: "in the brain, a groove running longitudinally along the lateral side of the cortex; typically found in many prosimians." &

cranial capacity: "the volume of the brain, usually determined by measuring the volume of the inside of the neurocranium." &

crenulation: "wrinkled surface of the tooth enamel of some primates." &

crepuscular: "active primarily around the hours of dawn and dusk." &

cristid obliqua: "ridge of enamel on the lower molars running obliquely from the hypoconid to the back of the trigonid." &

cursorial: "refers to a type of terrestrial locomotion characterized by fast running." &

cusp: "pointed or rounded protuberance on the occlusal surface of a tooth." &

cuspules: "small accessory cusps on teeth." &

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deciduous teeth: "teeth that are shed and replaced by other teeth during the normal course of a mammal's lifetime." &

dental alveoli: "sockets in the jaws that house the tooth roots." &

dental formula: "shorthand notation denoting the number of teeth in each quadrant of the upper and lower jaws; for example, 2:1:3:3/1:0:2:3 denotes two incisors, one canine, three premolars, and three molars on each side of the upper jaw and one incisor, no canines, two premolars, and three molars on each side of the lower jaw." &

diastema: "space or gap between adjacent teeth in the dental row." &

digitigrade: "refers to a type of quadrupedal locomotion in which animals support their body weight on their phalanges." &

distal: "further away from any line of reference; in dentition, refers to the side of the tooth or portion of the jaw toward the back of the mouth." &

diurnal: "active primarily during daylight hours." &

dolichocephalic: "having a long, narrow skull." &

dryomorph: "vernacular term to describe a group of primitive catarrhines found mainly in the Miocene of Africa and Europe." &

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ectotympanic bone: "bone in the middle ear that supports the tympanic membrane or eardrum." &

encephalization quotient (EQ): "measure of relative brain size in which the brain weight is compared with that of the average living mammal of equal body weight." &

endocast: "naturally occurring (fossilized) or artificially made mold of the external surface of the brain." &

endothermic: "describes 'warm-blooded' animals that maintain a fairly constant internal temperature through metabolic processes." &

entoconid: "cusp on the lingual rim of the talonid of lower molars." &

entocuneiform: "one of the small bones of the mammalian foot that articulates with the first metatarsal, the mesocuneiform, and the navicular." &

ethmoid bone: "small bone in the skull that contributes to the medial orbital wall in some primates and also forms a small portion of the floor of the braincase under the frontal bones." &

eversion: "turning outward, for example, of the bottom of the foot." &

extant: "currently existing; not extinct." &

external auditory tube: "outer-ear passage."

exudate: "a substance, such as gum, sap, or resin, which flows from the vascular system of a plant." &

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fenestra cochleae: "the 'round' window on the medial surface of the middle ear covered by the secondary tympanic membrane; also called the fenestra rotunda." &

folivorous: "leaf eating." &

folivore: "animals whose primary source of food is foliage (leaves)." &

foramen magnum: "large hole in the base of the skull through which the spinal cord passes, joining the base of the brain." &

frenulum: "small fold of skin immobilizing the upper lip; present in all extant strepsirhines but reduced or absent in extant haplorhines." &

frontal sinus: "air space found in the frontal bone." &

frugivorous: "fruit eating." &

frugivore: "animals whose primary source of food is fruit." &

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glabella: "area on the frontal bone between the brow ridges." &

gracile: "describes any slender, lightly built body or body part." &

Grand Coupure: "refers to the time near the end of the Eocene when many faunal groups, including primates, became extinct in the Northern Hemisphere." &

granivorous: "grain eating." &

granivore: "animals that eat primarily grains, although the term is sometimes used to describe animals that eat seeds as well." &

greater trochanter: "that part of the proximal femur where the gluteus medius and gluteus minimus attach." &

gummivorous: "gum eating." &

gummivore: "animals that eat primarily gums, saps, and other tree exudates." &

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hallux: "first digit on the hindlimb foot ('big toe')." &

hard palate: "bony separation between the oral and nasal cavities." &

homologous: "describes a similarity of form or structure between two species that they share with their nearest common ancestor." &

honing facet: "surface on the anterior portion of the anterior lower premolar (a sectorial tooth) used to sharpen the posterior edge of the upper canine when the two teeth come into contact." &

humerofemoral index: "ratio of the length of the humerus divided by the length of the femur X 100." &

hypocone: "cusp on the posterior lingual surface of the upper molars." &

hypoconid: "cusp on the lateral rim of the talonid of lower molars." &

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iliac pillar: "a bony buttress running down the iliac blade in hominids for resisting the powerful muscular forces generated by the hip abductor muscles." &

incertae sedis: "of uncertain taxonomic position; placed after the name of a taxon at any level of a classification hierarchy to indicate that the affinities of that taxon are not precisely determinable." &

incisiform: "shaped like an incisor." &

infraorbital foramen: "external opening of the infraorbital canal on the anterior surface of the maxilla for passage of blood vessels and nerves to the lower surface." &

insectivorous: "insect eating." &

insectivore: "any mammal whose primary source of food is insects." &

intermembral index: "ratio of the length of the forelimb (humerus + radius) divided by the length of the hindlimb (femur + tibia) X 100." &

interorbital distance: "distance between the orbits measured at their medial margins." &

inversion: "turning inward, for example, of the sole of the foot." &

isometry: "change in overall size of an object or organism that maintains the same shape." &

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Jarmin-Bell principle: "rule relating body size of mammals to the nutritional quality of the foods they eat: small mammals eat high-quality (high-energy), quickly digested foods such as insects, while larger mammals, needing relatively fewer calories per unit of body weight, can subsist on more low-quality, harder-to-digest foods processed in bulk, such as leaves." &

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Kay's threshold: "approximate body weight (around 500 g) that separates primarily insectivorous from noninsectivorous primates." &

knuckle walking: "type of quadrupedal locomotion in which the upper body is supported by the dorsal surfaces of the middle phalanges of the hand; practiced by chimpanzees and gorillas." &

kyphosis: "dorsally convex curvature of the back." &

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lacrimal bone: "in the skull, a small bone forming part of the medial orbital wall." &

lacrimal foramen: "opening of the tear duct connecting the orbit with the nasal cavity." &

lacrimal fossa: "the depression in which the lacrimal foramen sits." &

lateral sulcus: "on the brain, the groove on the lateral side of each cerebral hemisphere that separates the temporal lobe from the frontal and parietal lobes; also called the sylvian sulcus." &

laterocone: "small pointed cusp on the lateral side of the incisors of some plesiadapiforms." &

lemurophile hypothesis: "hypothesis of primate phylogeny that considers the plesiadapiforms to be the sister group of the omomyids and tarsiers (all three groups comprising the Plesitarsiiformes) and lemurs, lorises, and adapids to form a sister group of the anthropoids (together comprising the Simiolemuriformes)." &

lesser trochanter: "protuberance on the femur for attachment of the iliopsoas muscle, a flexor of the thigh." &

lingual: "toward the tongue." &

loph: "transverse crests on molars." &

lordosis: "ventrally convex curvature of the back." &

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mandibular body: "horizontal portion of the mandible; also called the horizontal ramus of the mandible." &

mandibular fossae: "shallow depressions, one on either side of the base of the skull, into which the mandibular condyles fit." &

mandibular symphysis: "the midline joint connecting the two sides of the mandible." &

mandibular torus: "shelflike thickening of bone on the inside of the mandibular symphysis; superior and inferior transverse tori are two transverse bony supports on the posterior side of the mandibular symphysis. The inferior transverse torus is often referred to as the simian shelf." &

manus: "hand." &

maxillary sinus: "air space within the maxillary bone." &

medial torsion: "an inward rotation along a longitudinal axis." &

mediocone: "small cusp on the front of the incisors of some plesiadapiforms." &

megadont: "having large teeth relative to body size." &

mesial: "toward the anterior side of a molar or premolar tooth or to the side of an incisor tooth nearest the midline of the jaw." &

metacone: "one of three primary cusps on the crown of upper molars; found on the posterior buccal (outer back) corner of the tooth." &

metaconid: "one of three main cusps on the trigonid (anterior triangular portion) of lower molars; found on the distal lingual (inner back) corner of the trigonid." &

metacrista: "ridge of enamel extending from the metacone in the upper molars of primitive eutherians and early primates." &

metopic suture: "midline joint between the two frontal bones in the skull." &

molariform: "molarlike in form and function." &

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nasal incisive foramen: "opening of the incisive canal into the nasal cavity; in some primates the foramen widens into a fossa at the opening." &

nasoalveolar clivus: "portion of the premaxilla extending from the nasal cavity to the incisor root sockets." &

navicular: "small bone that articulates with the talus in the mammalian foot." &

negative allometry: "an allometric relationship in which the slope of the line comparing two variables is less than unity." &

neocortex: "cerebral hemispheres." &

neoteny: "the retention of the features of a juvenile animal of one species in the adult form of a different species." &

neurocranium: "portion of the skull enclosing the brain, as distinct from the facial bones and the basicranium." &

nocturnal: "active primarily during the night." &

nuchal crest: "bony shelf on the back of the skull for the attachment of powerful neck muscles." &

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obturator foramen: "space in the pelvis enclosed by the pubis, ischium, and ilium." &

occipital bone: "bone forming the posterior and much of the basicranium of the mammalian skull." &

occlusal: "refers to the surfaces of the teeth that meet during occlusion (chewing)." &

olecranon fossa: "depression at the posterior side of the distal humerus for accommodating the olecranon process of the ulna when the elbow is extended." &

olecranon process: "projection on the proximal end of the ulna for attachment of the triceps muscle; the elbow." &

omomyophile hypothesis: "hypothesis of primate phylogeny that considers the omomyids to be the sister group of the tarsiers." &

ontogenetic: "relating to the growth and development of an individual organism." &

oral incisive foramen: "opening of the incisive canal into the oral cavity of the skull; in some primates the foramen widens into a fossa at the opening." &

orbit: "bony socket for the eye." &

orbital convergence: "realignment of the visual axes of the orbits during primate evolution from laterally facing to anteriorly facing lines of sight." &

orbitosphenoid bone: "portion of the sphenoid bone that forms part of the posterior wall of the orbit." &

orthognathus: "having a relatively vertical, nonprotruding face." &

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palatine process: "horizontal portion of the maxilla forming the hard palate." &

paleomagnetic column: "depiction of the alternating normal and reversed polarity epochs through geological time." &

palmigrade: "refers to a type of quadrupedal locomotion characterized by weight bearing on the palms of the hands rather than on the digits or knuckles." &

palynology: "study of plant pollens." &

paracone: "one of three primary cusps on the crowns of primate upper molars; found on the mesial buccal (outer front) corner of the tooth." &

paraconid: "cusp on the mesial lingual surface of the lower molars." &

paracrista: "enamel ridge running from the paracone in the upper molars of primitive mammals and early primates." &

parasagittal: "refers to a plane through the body parallel to the sagittal plane, which divides the body into left and right sides." &

parietal bone: "flat bone forming part of the lateral wall of the skull." &

patella: "kneecap." &

patellar groove: "depression on the distal femur in which the kneecap (patella) moves." &

petrosal bone: "portion of the temporal bone that forms the auditory bulla in primates." &

phalanges: "finger and toe bones." &

philtrum: "vertical cleft in the rhinarium of extant strepsirhines; not present in haplorhines." &

phylogeny: "evolutionary or geneological relationships among a group of organisms." &

plagiaulacoid dentition: "dentition in which the molars and premolars are arranged like a cutting board and cleaver; characteristic of carpolestids and saxonellids." &

plantar: "pertaining to the sole of the foot." &

pneumatized: "filled with air spaces, as in pneumatized portions of the skull." &

polarity epoch: "a sustained period of time characterized by either normal or reversed magnetic polarity." &

polarity event: "short-lived polarity reversal occurring within a polarity epoch." &

pollex: "thumb." &

polymorphic: "showing a variety of forms." &

positive allometry: "allometric relationship in which the slope of the line comparing two variables is greater than unity." &

postcanine dentition: "all the teeth distal to (in back of) the canines: premolars and molars." &

postcranial skeleton: "all of the skeleton, except the skull, that is, the limbs and vertebral column." &

posterocone: "small, pointed cusp at the back of the incisors of some plesiadapiforms." &

postorbital bar: "bony ring surrounding the lateral side of the orbit in lower primates and many other mammals." &

postorbital closure: "'walling off' of the orbit posteriorly by means of a bony partition so that the orbit forms a cup-shaped structure." &

postorbital constricition: "narrowing of the skull behind the orbits." &

postprotocingulum: "structure occurring on the upper molars of some early primates in which a ridge of enamel runs from the distal lingual corner of the protocone to the cingulum; also called the Nannopithex fold." &

prehallux: "small sesamoid (accessory) bone sometimes occurring in the tarsometatarsal joint of the hallux." &

prehension: "ability to grasp objects with hands or feet." &

premaxilla: "bony part of the upper jaw that houses the incisors." &

premolariform: "shaped like a premolar." &

procumbent: "refers to incisors that project more in the horizontal than in the vertical plane." &

prognathus: "having a protruding jaw in which the bone housing the incisors projects anteriorly." &

promontory artery: "one of the two branches of the internal carotid artery in the middle ear of primates." &

pronation: "medial rotation of the forearm to turn the palm backward or downward." &

protocone: "one of three main cusps on the crowns of primate upper molars; found on the lingual side of the tooth." &

protoconid: "one of three main cusps on the trigonid (anterior triangular portion) of lower molars; found on the buccal side of the tooth." &

proximal: "closer to any particular point of reference." &

pseudohypocone: "type of cusp that develops through cleavage of the protocone, unlike the true hypocone, which arises from the cingulum; found in Eocene notharctines." &

pterion: "temple region of the skull." &

pterygoid plates: "bony plates on the inferior surface of the sphenoid bone for attachment of two muscles of mastication, the lateral and medial pterygoid muscles." &

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quadritubercular: "having four cusps; refers to a four-sided (squarish) molar tooth." &

quadrumanous: "four-handed; as in quadrumanous climbing, in which many suspensory primates use their feet in the same manner that they use their hands." &

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reversed polarity epoch: "periods of geological time in which the magnetic field points to the south." &

rhinarium: "hairless patch of skin between the nose and upper lip; present in extant strepsirhines." &

robust: "describes any large, or heavily built body part." &

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sagittal crest: "bony crest running along the midline of the skull for attachment of enlarged temporalis muscles." &

scapula: "shoulder blade." &

schizodactyly: "grasping between the second and third digits of the hand rather than between the pollex (thumb) and second digit." &

sciatic notch: "broad notch on the posterior surface of the pelvis separating the ilium and ischium; prominent in humans and later australopithecines but not in earlier primates." &

sectorial tooth: "tooth in the lower jaw (usually the anterior premolar) with a honing facet for sharpening the upper canine during occlusion." &

sexual dimorphism: "phenomenon in which homologous nonreproductive structures are of greatly different size and/or shape in males and females of the same species." &

sigmoid notch: "concave surface at the proximal end of the ulna that articulates with the trochlea of the humerus." &

spatulate: "spatula-shaped; refers to incisors that are broad." &

sphenoid sinus: "air cavities within the sphenoid bone." &

sphenoid bone: "irregularly shaped bone forming part of the base of the skull." &

squamosal sinus: "suture between the parietal and temporal bones." &

stapedial artery: "one of the two branches of the internal carotid artery in the middle ear of primates." &

stylar shelf: "shelflike extension of enamel on some cheek teeth." &

subnasal alveolar process: "part of the premaxilla housing the roots of the upper incisors." &

subfossil: "recently extinct, often from historical time periods. Some prosimians from Madagascar, for example, have become extinct in the past thousand years." &

supination: "rotation of the forearm so that the palm faces forward." &

supraglabella: "forehead region." &

supraorbital tori: "brow ridges." &

supratoral sulcus: "groove in the skull between the brow ridges and the frontal bone." &

suspensory posture: "behavior characterized by suspension of the body below branches." &

suture: "a joint between two bones in which the bones interdigitate and are separated by fibrous tissue." &

symphysis: "one of several fibrocartilaginous joints found in the midline of the body, such as the mandibular symphysis and the pubic symphysis." &

synostosis: "union of adjacent bones formed by an osseous material." &

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talonid: "posterior heellike portion of lower molars." &

talus: "ankle bone; also called the astragalus." &

taphonomy: "study of the processes by which animal bones become fossilized." &

tarsiphile hypothesis: "hypothesis in primate phylogeny that considers tarsiers to be the sister group of the platyrrhines and catarrhines." &

temporal bone: "bone of the skull that forms part of the lateral wall of the skull and covers the various structures of the ear." &

temporal fossa: "space enclosed by the side of the skull and the zygomatic arch which is occupied by the temporalis muscle." &

temporonuchal crest: "compound bony crest on the skull formed by convergence of the temporal lines (or sagittal crest) and the nuchal crest." &

terrestrial quadruped: "ground-living animal that moves about primarily on all four limbs." &

tibial malleolus: "medial portion of the distal tibia forming the medial part of the ankle joint." &

tooth comb: "a formation of the lower incisors into a comblike structure for grooming." &

trigone: "portion of the upper molars formed from the three main cusps: protocone, metacone, and paracone." &

trigonid: "anterior triangular portion of the lower molars; contains the paraconid (when present), protoconid, and metaconid." &

tritubercular: "having three cusps; refers to a triangular-shaped tooth." &

trochlea: "any smooth, saddle-shaped bony surface that resembles a pulley as it articulates with other bones; specifically, in the elbow joint surface on the humerus that articulates with the ulna; in the knee joint the surface on the femur that articulates with the patella; and in the ankle joint the surface on the talus that articulates with the tibia." &

tympanic bone: "the bone that forms the bony ring for the eardrum." &

tympanic membrane: "eardrum." &

type locality: "site from which the type specimen for a particular species or rock unit was taken." &

type species: "species for which a genus or higher-level taxon was first named and described." &

type specimen: "individual specimen – usually the first to be found for a particular species – that serves as the basis for identifying all other individuals of the same species. Also called a holotype." &

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valgus: "an angulation of the femur such that the knees are closer together than the hip joints; 'knock-kneed.'" &

ventral: "toward the belly side of an animal; the opposite of dorsal." &

vertcal clinging and leaping: "a type of locomotion and posture in which animals cling to vertical supports and move by leaping between these vertical supports." &

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zygomatic_arch: "bony arch on the lateral part of the skull formed by projections of the zygomatic bone and the temporal bone for attachment of the masseter muscle." &

REFERENCES:
The colored symbol & denotes the source of the definition.

&: Primate Evolution by G.C. Conroy. W.W. Norton and Co.: New York. 1990.

&: Primate Adaptation and Evolution by J.G. Fleagle. Academic Press: San Diego. 1988.

Last updated: November 13, 2001

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