Early Primates

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					Early Primates
         Ancestral Primates
• Plesiadapiformes – early mammals,
  abundant during Paleocene
• Could be precursor to primates

• ~55 mya first true primates appear
  – Adapids and omomyids
  – Were prosimians
         Ancestral primates
• Adapids and omomyids possessed all
  typical primate characteristics
  – Postorbital bars
  – Larger brains
  – Reduced snouts
  – Grasping hands and feet
  – Nails – no claws
• Called Euprimates
• Appeared in Eocene after
  plesiadapiformes went extint
         Ancestral primates
• Early arboreal primates survived better
  than terrestrial

• Probably due to competition from rodents
• Range also constricted by competition
  from bats at this time
     Early primate adapations
• Most early primate evolution occurred in
  the trees, so most traits are related to
  adapations for arboreal living
• Diet adaptations moved away from
  insectivorous to vegetative
• Moved away from tall sharp cusps for
  slicing to flatter cusps better for grinding
             Plesiadapiforms
• Mammals, not primates (precursors?)
• Families
    – Plesiadapidae, Paromomyidae,
      Picrodontidae, Saxonellidae
•   35 genera
•   150 g to 3 kg
•   Insectivores
•   Snout, non-opposable hallux, claws
         Precursors or not?
• Too young
• Too specialized

• Crania show primate-like adaptations

• Post crania, not so much
                 Euprimates
• Spotty fossil record at time of origin
• Dental and postcranial characters typically
  primate
    – Increased reliance on fruits and seeds
•   Very similar to modern prosimians
•   Adapiformes – largely Europe
•   Omomyids – largely N America
•   75 genera
             adapiformes
• Affinities to modern
lemurs
• Some believe lemurs
direct descendents,
preserving primitive
Morphology
Includes Notharctus
Adapis
              Omomyids
• Tarsiiformes
• 1 kg (smaller than adapids)
        Arboreal adaptations
• Seen in earliest euprimates
  – Stereoscopic vision w/ reduced nose
  – Diurnal activity pattern
  – Color vision
  – Enclosed orbit
  – Unfused radius and ulna
  – Pentadactyly
  – Loss of naked rhinarium
         Adaptive scenarios
• Arboreal hypothesis
  – Tree dwelling

• Visual predation theory
  – Expanded previous

• Angiosperm Exploitation hypothesis
  primates evolved in conjunction with
  flowering plants

				
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