Biological Classification of the Living Primates

Analogies

• Analogy = a feature that evolves independently in different groups as a result of similar evolutionary pressures resulting in similar adaptations.

Homologies

• Homology= a characteristic that is similar in various groups of organisms because of their origin from a common ancestor possessing that characteristic.

Primitive vs. Derived

• Primitive feature = features that are similar in form to that of an ancestor.
• Derived feature = features that have undergone change from the ancestral form.

Biological Classification

• Binomial nomenclature = classificatory system for organisms devised by Linnaeus featuring the binomen (genus and species).
• Genus = taxonomic level above species and bellow subfamily; a group of closely related species.
• Species = a group of individuals that can potentially interbreed and produce fertile offspring (biological definition of species).

Biological Classification

How do we determine taxonomic relationships?

1. Recency of divergence – how recently two groups shared a common ancestor.

For example, Homo sapiens and Pan troglodytes last shared a common ancestor 5-7 mya.

2. To what extent the groups diverged – how much each group has changed in the time since they shared a common ancestor.

The Order Primates

• Kindom: Animalia
  • Phylum: Chordata
    • Subphylum: Vertebrata
      • Class: Mammalia
        • Order: Primates
          • Family: Hominidae
            • Genus: Homo
              • Species: sapiens

The Order Primates

• Order originated approximately 65 million years ago.
• Habitat: tropics and subtropics in South America (New World) and Africa/Asia (Old World).
• Dietary Specializations:
  • Folivory (leaf-eating)
  • Frugivory (fruit-eating)
  • Gramnivory (seed-eating)
  • Gummivory (gum-eating)
  • Insectivorous (insect-eating)
  • Omnivorous (eat a variety of plants, fruits, nuts, protein, etc.)

Characteristics of Primates

1.) Retention of unspecialized limb structure:

• Retention of five fingers and five toes
• Retention of clavicle

2.) Nails rather than claws

3.) Grasping hind feet with opposable first toes

4.) Increased emphasis on vision:

• Forward facing eyes (allowing for better depth perception)
• Expanded occipital and temporal lobes of the brain.
• Color vision (in most primates)

5.) Complete ring of bone around the orbit:

• postorbital bar

6.) Enlarged brain relative to overall body size.

7.) Less emphasis on olfaction:

• Shortened snout
• Small olfactory bulb

8.) Longer period of fetal nourishment/development.

• Intrauterine development
• Prolonged stages of lifespan

9.) Longer period of infant dependency.

10.) Most live in social groups with well-developed communication systems.

Two Suborders

• Strepsirhini Prosimians
• Haplorhini Anthropoidea

Infraorder Strepsirhini

Prosimians

• Among oldest living primates.
• Developed sense of smell
  • Enlarged olfactory bulb & scent glands
• Combination of nails and claws
• Less dexterity
• Geographic range: Madagascar and Southeast Asia.
• Lemurs (ring-tailed, black and white ruffed), indri, safakia, lorises, galagos, pottos).

Infraorder Strepsirhini

• Relatively smaller brain
• No postorbital closure
• Orbits with more lateral orientation
• Unfused mandible
• Longer snout
• Moist rhinarium (nose)
• Toothcomb
• Grooming claw

Infraorder Tarsiiformes

• Vertical clingers and leapers.
• Huge eye orbits for nocturnality.
• Tapetum lucidum
• Unfused mandible.
• Grooming claw
• Molars with sharp, pointy cusps.
• Categorized differently depending upon the textbook!

Sub Order Haplorhini

• Relatively larger brain
• Postorbital closure
• Orbits with more forward orientation
• Fused mandible
• Molars with flatter cusps
• Shorter snout
• Continuous upper lip
• Nails on all digits

Infraorder Platyrrhini

New World Monkeys

• One subfamily:
  • Ceboids
  • Spider monkeys, squirrel monkeys, capuchins, tamarin, marmosets, howler monkeys, woolly monkeys, saki, uakari
• Side-directed nostrils
• Dental formula: 2-1-3-3
• No bony ear tube
• Prehensile tail.
• Lower levels of sexual dimorphism
• Geographic Range: Central and South America

NWM: Prehensile Tails

Infraorder Catarrhini

Old World Monkeys, Apes, Humans

• Terrestrial and arboreal
• Geographic Range: Africa and Asia
• Two subfamilies:
  • cercophithecoids
  • colobines
• Baboons, macaques, mandrills, geladas, vervet monkeys, guenons colobus moneys

Cercopithecoidea

Old World Monkeys

• Forward or down-directed nostrils
• Dental Formula: 2-1-2-3
• Higher levels of sexual dimorphism.
• Bony ear tube
• Bilophodont molars (two cusps)
• Narrow thorax
• Tail (but not prehensile)
• Ischial callosities (tough sitting pads on the rear)

Colobus Monkeys and Langur

Bilophodont or Y-5?

Molars have different numbers of cusps.

• Bilophodont (two lobes). (found in Old World Monkeys)
• Y-5 (cusps in the shape of a “Y”). (found in Superfamily Hominoidea)

Ischial Callosites

• Tough sitting pads on the rear (ischial callosities).
• Old World Monkeys tend to rest in the sitting position.

Superfamily Hominoidea

Apes and Humans

• Largest relative brain size
• Y5 molar pattern
• Broad thorax
• No tail

SuperFamily Hominoidea

Lesser Apes:

(gibbon, siamang)

• Skilled brachiators.
• Long arms in comparison with legs.

Superfamily Hominoidea

Great Apes:

Orangutan, Chimpanzee, Bonobo, Gorilla

• Sagittal crest in gorilla, orangutan
• Chimpanzees and Humans omnivorous
• Humans characterized by skeletal structure for bipedalism

Sagittal Crest (Gorilla)