Primates: Evolution, Anatomy, and Locomotion Patterns

Activity pattern

Refers to the time of day an animal is typically active.

African clade

A grouping that includes gorillas, chimpanzees, bonobos, humans, and their extinct relatives.

Analogy

When two or more taxa exhibit similar traits that have evolved independently, the similar traits evolve due to similar selective pressures.

Ancestral trait

A trait that has been inherited from a distant ancestor.

Arboreal

A descriptor for an organism that spends most of its time in trees.

Asian clade

A grouping that includes orangutans and their extinct relatives.

Bilophodont

Molar pattern of cercopithecoid monkeys in which there are usually four cusps that are arranged in a square pattern and connected by two ridges.

Bipedalism

Walking on two legs.

Brachiation

A form of locomotion in which the organism swings below branches using the forelimbs.

Bunodont

Low, rounded cusps on the cheek teeth.

Canines

In most primates, these are the longest of the teeth, often conical in shape and used as a weapon against predators or others of their species.

Cathemeral

Active throughout the 24-hour period.

Clade

A grouping based on ancestral relationships; a branch of the evolutionary tree.

Cusps

The bumps on the chewing surface of the premolars and molars, which can be quite sharp in some species.

Dental formula

The number of each type of tooth in one quadrant of the mouth, written as number of incisors: canines: premolars: molars.

Derived trait

A trait that has been recently modified, most helpful when assigning taxonomic classification.

Diastema

A space between the teeth, usually for large canines to fit when the mouth is closed.

Dichromatic

Being able to see only blues and greens.

Diurnal

Active during the day.

Dry nose

The nose and upper lip are separated and the upper lip can move independently; sometimes referred to as a 'hairy' or 'mobile' upper lip.

Ethnoprimatology

A subarea of anthropology that studies the complexities of human-primate relationships in the modern environment.

Evolutionary trade-off

When an organism, which is limited in the time and energy it can put into aspects of its biology and behavior, is shaped by natural selection to invest in one adaptation at the expense of another.

Faunivorous

Having a diet consisting entirely of animal matter: insects, eggs, lizards, etc.

Folivore

Having a diet consisting primarily of leaves.

Fovea

A depressed area in the retina at the back of the eye containing a concentration of cells that allow one to focus on objects very close to one's face.

Frugivore

Having a diet consisting primarily of fruit.

Generalized trait

A trait that is useful for a wide range of tasks.

Grade

A grouping based on overall similarity in lifestyle, appearance, and behavior.

Grooming claw

A claw present on the second pedal digit in strepsirrhines.

Gummivore

Having a diet consisting primarily of gums and saps.

Heterodont

Having different types of teeth.

Homology

When two or more taxa share characteristics because they inherited them from a common ancestor.

Hone

When primates sharpen their canines by wearing them on adjacent teeth.

Incisors

The spatula-shaped teeth at the front of the mouth.

Insectivore

Having a diet consisting primarily of insects.

Ischial callosities

Modified seat bones of the pelvis that are flattened and over which calluses form; function as seat pads for sitting and resting atop branches.

Knuckle-walking

A form of quadrupedal movement used by Gorilla and Pan when on the ground, wherein the front limbs are supported on the knuckles of the hands.

Life history

Refers to an organism's pace of growth, reproduction, lifespan, etc.

Locomotion

How an organism moves around.

Male bimaturism

Refers to the alternative reproductive strategies in orangutans in which males can delay maturation, sometimes indefinitely, until a fully mature, "flanged" male disappears.

Molars

The largest teeth at the back of the mouth; used for chewing. In primates, these teeth usually have between three and five cusps.

Monochromatic

Being able to see only in shades of light to dark, no color.

Monomorphic

When males and females of a species do not exhibit significant sexual dimorphism.

Natal coat

Refers to the contrasting fur color of baby leaf monkeys compared to adults.

Nocturnal

Active at night.

Olecranon process

Bony projection at the elbow end of the ulna.

Opposable thumb or opposable big toe

Having thumbs and toes that go in a different direction from the rest of the fingers, allows for grasping with hands and feet.

Pentadactyly

Having five digits or fingers and toes.

Polymorphic color vision

A system in which individuals of a species vary in their abilities to see color. In primates, it refers to males being dichromatic and females being either trichromatic or dichromatic.

Postorbital bar

A bony ring that surrounds the eye socket, open at the back.

Postorbital closure/plate

A bony plate that provides protection to the side and back of the eye.

Prehensile tail

A tail that is able to hold the full body weight of an organism, which often has a tactile pad on the underside of the tip for improved grip.

Premolars

Smaller than the molars, used for chewing. In primates, these teeth usually have one or two cusps.

Quadrupedalism

Moving around on all fours.

Rhinariums

Wet noses; resulting from naked skin of the nose which connects to the upper lip and smell-sensitive structures along the roof of the mouth.

Sagittal crest

A bony ridge along the top/middle of the skull, used for attachment of chewing muscles.

Scent marking

The behavior of rubbing scent glands or urine onto objects as a way of communicating with others.

Semi-brachiation

A form of locomotion in which an organism swings below branches using a combination of forelimbs and prehensile tail.

Sexually dimorphic

When a species exhibits sex differences in morphology, behavior, hormones, and/or coloration.

Shearing crests

Sharpened ridges that connect cusps on a bilophodont molar.

Specialized trait

A trait that has been modified for a specific purpose.

Styloid process of ulna

A bony projection of the ulna at the end near the wrist.

Tactile pads

Sensitive skin at the fingertips for sense of touch. Animals with a prehensile tail have a tactile pad on the underside of the tail as well.

Tapetum lucidum

Reflecting layer at the back of the eye that magnifies light.

Terrestrial

A descriptor for an organism that spends most of its time on the ground.

Tetrachromatic

Having the ability to see reds, yellows, blues, greens, and ultraviolet.

Tooth comb or dental comb

A trait of the front, lower teeth of strepsirrhines in which, typically, the four incisors and canines are long and thin and protrude outward.

Trichromatic color vision

Being able to distinguish yellows and reds in addition to blues and greens.

Vertical clinging and leaping

A locomotor pattern in which animals are oriented upright while clinging to vertical branches, push off with hind legs, and land oriented upright on another vertical branch.

Y-5 molar

Molar cusp pattern in which five molar cusps are separated by a "Y"-shaped groove pattern.