Lecture 10 -- The Primates: Adaptive Trends

Ancestral Traits

Features primates share with other placental mammals

Ancestral traits of primates

Mammary glands (produce milk to nourish young), homeothermy (fur for insulation, sweat glands), heterodonty (incisors, canines, premolars, molars), Bigger neocortex, placenta and long gestation followed by live birth, maternal care of the young

3 Major groups of mammals

Eutherian mammals (placental), Marsupitals (live birth, part dev. embryo), Monotremes (egg laying

6 Major groups of primates

Lemur, lorises/galagos, tarsiersmonkeys of america, monkeys of Asia and Africa, apes

Strepsirrhine

Prosimians (lemurs, lorises, galagos, tarsiers)

Haplorhine

Anthropoids (Monkeys and apes)

Anthropoids

Platyrrhine and catarrhine

Platyrrhine

Monkeys of America

Catarrhine

Cercopithecoids and Apes

Cercopithecoids

Monkeys of Asia and Africa

Apes

Apes

Petrosal bulla

A bony structure protecting the middle ear. The single trait that characterizes all primates, to the exclusion of other mammals

Derived homologies

Petrosal bulla, high degree of grasping ability in the hands and feet (opposable thumb and big toe, nails instead of claws, tactile pads on end digits), decreased reliance on smell (particularly in haplorhines; haplorhines lack a moist nasal rhinarium and their nasal structures of the skull are reduced), stereoscopic vision (haplorhines have trichromatic vision), post orbital bar, large brain relative to body size, prolonged life, single offspring, socialites

Ancestral traits of primates

Generalized body plan (retention of the clavicle, two seperate bones in lower arm [ulna and radius], five digits in hands and feet), generalized dentition, diversity in locomotor and dietary adaptations

Quadrupedalism (Terrestrial [on the ground] or Arboreal [living in trees])

Hind limbs and forelimbs are near equal length, arboreal have long tails for balance, shoulder blade position to side of ribcage (restricted movement at the shoulder), long flexible lower back

Vertical clinging and leaping

Long powerful hind limbs, long flexible back, long fingers for grasping supports when they land

Suspensory (incl. brachiation)

Short hind limbs, elongated forelimbs, mobile shoulder joints, shoulder blades on back, long curved finger

Brachiation

A form of aborreal locomotion when primates (usually apes) swing hand-over-hand from branch to branch using only their arms

Knuckle-walking

Form of quadrupedalism practiced by great apes, wrist joints stabilized

Primates dentition

low, rounded cusps; generalized dentition that allows them to process most types of food

General features of primates dentition

Teeth in upper and lower jaw, bilaterally symmetric, heterodont dentition (incisors, canines, premolars and molars)

Dental classes

Posterior teeth; chewing, anterior; ingestion, incisors; cut food, canines; tear food and behavioral function, premolars and molars; crushing and grinding

Dental formula - ancestral mammal

3.1.4.3

Dental formula - Most strepsirhines, tarsiers, and platyrrhine monkeys

2.1.3.3

Dental formula - Cercopithecoid monkeys, apes, and humans

2.1.2.3

Dental adaptation - insectivory

Sharp crests for puncturing the outer skeleton of insects

Dental adaptation - frugivory

Low cusps for crushing soft fruits

Dental adaptation - folivory + Folivore-Frugivore

Well-developed shearing crests for cutting tough leafy material into small pieces