Primate Diversity II: Haplorrhines, Monkeys, and Apes

I. Overview of Haplorrhines

Haplorrhines are a suborder of primates that include tarsiers, monkeys, and apes (including humans). They are often referred to as “simple” or “dry-nosed” primates due to their lack of a rhinarium (wet nose) seen in strepsirrhines (lemurs and lorises).

II. Tarsiiformes (Tarsiers)

Taxonomy & Distribution

• Infraorder: Tarsiiformes

• Family: Tarsiidae

• Genus: Tarsius

• Geographical Distribution: Southeast Asia (Philippines, Borneo, Sumatra, Sulawesi)

Physical and Behavioral Characteristics

• Size: Small, rat-sized primates

• Locomotion: Vertical clingers and leapers (VCL) – highly specialized for jumping

• Activity Pattern: Nocturnal (active at night)

• Diet: 100% faunivorous (insects, reptiles, birds, worms)

• Social Structure:

  • Some species are solitary

  • Others live in small groups

• Unique Features:

  • Large eyes (each eye is larger than their brain or stomach!)

  • Enclosed orbits (unlike strepsirrhines)

  • Elongated ankle (tarsal) bones, giving them their name

  • No dental comb

  • Lack rhinarium (dry nose)

Newly Discovered Tarsier Species

• Gursky’s spectral tarsier (Tarsius spectrumgurskyae) – Found in Sulawesi, Indonesia

• Jatna’s tarsier (Tarsius supriatnai)

• Since 2000, over 80 new primate species have been discovered, highlighting ongoing biodiversity findings.

III. Anthropoidea (Monkeys, Apes, Humans)

Key Differences Between Anthropoids & Strepsirrhines/Tarsiers

1. Larger body size

2. Larger brain relative to body size

3. Reduced reliance on olfaction (sense of smell)

4. Increased reliance on vision

   • Better color vision

   • Post-orbital closure (full bony eye socket)

5. Mandibular fusion (lower jaw fused in adults)

6. More generalized dentition

7. Longer gestation and maturation periods

8. More complex parental care

9. Increased mutual grooming (important for social bonding)

Two Major Anthropoid Groups (Parvorders)

1. Platyrrhini (New World Monkeys - NWM)

2. Catarrhini (Old World Monkeys & Apes - OWM & Hominoidea)

IV. Platyrrhini (New World Monkeys)

Key Features

• Distribution: Tropical & subtropical regions of the Americas (Southern Mexico, Central & South America)

• Five extant families:

  • Atelidae

  • Pitheciidae

  • Cebidae

  • Callitrichidae

  • Aotidae

• Evolutionary History: Likely arrived from Africa ~50 million years ago via rafting (floating on vegetation mats).

• Ecological Adaptations:

  • Less adaptive diversity than strepsirrhines and catarrhines

  • Some have prehensile tails for grasping

  • Primarily arboreal and diurnal

Platyrrhine Eyesight & Color Vision

• Most NWMs have polymorphic trichromacy (some individuals can see in full color while others are dichromats).

• Exceptions:

  • Owl monkeys – monochromatic (see in black & white, nocturnal)

  • Howler monkeys – all individuals are trichromatic

Platyrrhine Locomotion & Mating Systems

• No habitual terrestrial species

• Some descend to the ground for water, mineral licks, or crossing open spaces.

• Mating Systems:

  • Monogamy

  • Polygyny

  • Polyandry

  • Polygynandry

Unique Features of Platyrrhines

1. Prehensile tails (Spider monkeys & Capuchins)

2. Loudest calls (Howler monkeys – can be heard from 3 miles away!)

3. Re-evolved claws (Marmosets & Tamarins – a primitive trait)

4. Capuchins = “vacuum cleaners of the forest” – highly adaptive, eat almost anything

V. Catarrhini (Old World Monkeys & Apes)

Key Features

• Distribution: Africa and Asia

• Dental Formula: 2.1.2.3

• Larger & more sexually dimorphic than platyrrhines

• Two Major Groups:

  1. Cercopithecoidea (Old World Monkeys - OWM)

  2. Hominoidea (Apes & Humans)

VI. Cercopithecoidea (Old World Monkeys)

General Characteristics

• More widely distributed than any other primate group (except humans)

• Both arboreal & terrestrial species

• Some species live in extreme environments (e.g., snow monkeys in Japan)

Two Major Subfamilies

1. Cercopithecinae (Cheek-Pouch Monkeys)

   • Omnivorous

   • Diurnal

   • More terrestrial species (e.g., baboons, macaques)

   • Store food in cheek pouches

2. Colobinae (Leaf-Eating Monkeys)

   • Primarily folivorous (leaf-eating)

   • Specialized stomachs for digesting leaves (foregut fermentation, similar to cows!)

   • More arboreal than cercopithecines

VII. Hominoidea (Apes & Humans)

Differences Between Apes & Monkeys

1. No tail

2. Larger body size

3. More complex social behavior

4. More upright posture

5. Longer arms than legs (except humans)

6. More flexible shoulder joints

Two Families of Apes

1. Hylobatidae (Lesser Apes – Gibbons & Siamangs)

   • Found in Southeast Asia

   • True brachiators (swing through trees with long arms)

   • Pair-bonded males & females – defend their territories by singing duets

2. Hominidae (Great Apes – Gorillas, Chimpanzees, Orangutans, Humans)

   • More complex social structures

   • Larger brain sizes

VIII. Great Apes (Family Hominidae)

Gorillas

• Largest living primates (~500 lbs. for males)

• Herbivorous

• Extreme sexual dimorphism (males much larger than females)

Orangutans

• Only diurnal & solitary primate

• Critically endangered

• Sexual dimorphism: Males develop flanged faces, while others remain “unflanged” (smaller & sneak-mate).

Chimpanzees vs. Bonobos

• Common Chimps (Pan troglodytes)

  • More aggressive & territorial

  • Engage in lethal warfare

• Bonobos (Pan paniscus)

  • Less aggressive, matriarchal societies

  • Resolve conflicts through sociosexual behaviors (“make love, not war”)

IX. Summary

• Primates are highly diverse, with unique ecological & behavioral adaptations.

• Monkeys are a grade-based term, not a natural group.

• New World Monkeys (Platyrrhini) are different from Old World Monkeys (Catarrhini).

• Apes are the most behaviorally complex primates, leading to human evolution.