What is the Evolutionary History of the Primates?

1
What is the Evolutionary History of the Primates?
2
Cenozoic Timescale
3
What is the Evolutionary History of the Primates?

• 1. EOCENE 54-38 mya
• Prosimian Radiations
• 2 exs Smilodectes, Necrolemur
• 2. OLIGOCENE 38-23 mya
• Monkey Radiations
• 2 exs Apidium, Aegyptopithecus
• 3. MIOCENE 23-5 mya
• Ape Radiations
• 2 exs Sivapithecus, Gigantopithecus,
  Sahelanthropus

4
Late Cretaceous Primate-like Mammal Purgatorius
Last Common Ancestor lived sometime in the late
Cretaceous when dinosaurs still dominant
land-dwelling life form genetic evidence
diversity of primates from the Eocene and later

• However, fossils of true primates are not known
  until approximately 50 mya during the Eocene
• During the late Cretaceous (gt65 mya), ancestral
  shrew-like mammals show certain dental and limb
  bone features reminiscent of true primates

5
Primate Origins
If the last common ancestor of living primates
did indeed live between 80 and 90 mya, the
primate lineage that we are descended from would
be pushed back more than 30 million years!
6
New Discoveries of Early Primates
New discoveries from Eocene of China reveal an
unexpected diversity of early primates

• Some ancestors of monkeys, apes and humans were
  so tiny that they could have stood atop a
  persons thumb
• Fossilized foot bones from 2 species smaller than
  any other known creature on the primate family
  tree were found at a limestone mine in Eastern
  China, bones each about the size of a grain of
  rice!

7
Eocene Primates (Prosimian radiations) 1.
Smilodectes (North America)

• Like modern lemurs it
• was hind-limbed dominated, indicating ability to
  leap long distances
• had hands feet w/nails
• had supple, flexible spine
• Unlike modern lemurs it
• had generalized dentition lacking toothcomb, but
  retained large canines
• had fused lower jaw
• shortened muzzle

8
Eocene Primates 2. Necrolemur (Europe)
Very similar to the modern tarsier. Its features
included

• Elongated ankle bones similar to those seen in
  Tarsius, indicative of clinging leaping
• Reduced snout and enlarged orbits, indicative of
  nocturnal adaptation
• More generalized dentition showing adaptations
  for insect eating
• Ears and eyes like modern tarsiers, but may have
  retained a wet nose

Necrolemur
Tarsius
9
Oligocene Primates Anthropoids(Monkey
radiations)

• Anthropoids most likely branched off from the
  prosimians much earlier than previously thought.
  Their distinguishing features are
• Eyes rotated more forward compared to prosimians
• Fully enclosed bony eye socket
• Dry nose separate from the upper lip
• Relatively low crowned, squared off chewing teeth

10
Oligocene Primates El Fayum, Egypt

• Over the last 40 years, Anthropologists have
  excavated a fossil rich oasis in Egyptian Saharan
  desert called the Fayum depression
• Late Eocene Oligocene the Fayum was a lush
  tropical environment crisscrossed by myriad
  streams and rivers
• Diverse abundant mammals

11
Oligocene Primates 1. Apidium

• Dental formula of 2133 on both upper and lower
  jaws as in New World monkeys
• Short snout small eyes suggest that this was a
  diurnal species
• Postorbital closure
• Platyrrhine-like skeleton

12
Oligocene Primates
2. Aegyptopithecus

• Face Aegyptopithecus, just after discovery in the
  river channel sands of the Fayum, about 32 mya
• lies somewhere near the base of the family tree
  of Old World monkeys, apes and humans
• generalized arboreal quadruped, with different
  sized sexes, traveled through ancient Egyptian
  jungles in small multi-male, multi-female troops,
  diet thought to have been mainly fruits and leaves

13
Aegyptopithecus
Oblique View
14
Aegyptopithecus
Lateral View
15
Miocene Primates (Ape radiations)
1. Sivapithecus

• Discovered in Pakistan
• Most anthropologists convinced of its
  relationship to the Orangutan (left)
• Points of resemblance to modern Orangs

1. Deep, concave face with large front teeth
2. Narrow distance between the eye orbits
3. Oval shape eye orbits
4. Pear-shaped nasal opening
5. Rim of bone around the upper margin of the orbits

16
Miocene Primates
2. Gigantopithecus

• Largest primate that ever lived, thought by some
  to stand over 10 tall and weigh close to 1200
  lbs.
• Died out around 400,000 ya, may have coexisted
  with Homo erectus
• Some people believe it is still alive today as
  the yeti and bigfoot

• These three lower jaws are twice the size of a
  Gorillas
• most complete specimens known, discovered in a
  limestone cavern in China in 1956

17
Miocene Primates
3. Sahelanthropus

• Discovered in Chad (6-7 mya)
• Most complete cranium from this period of time
  GREAT value in understanding last common ancestor
  of African apes humans
• Mosaic of ape human-like features, but is at
  the ape grade of evolution
• Features include
• Ape-like cranial capacity (320-380 cc)
• Ape-like narrow U-shaped upper jaw
• Very wide distance between the orbits
• Large, thick continuous brow ridge
• Human-like flat face
• Human-like dentition

18
Ecological Reconstruction

• Mammals found in association with Sahelanthropus
  are Eurasian and African forms that indicate
  migration into Africa
• Migration probably due to colder drier climate
  in Eurasia
• Late Miocene apes occur for the most part in
  Europe and Asia several of these species may be
  hominid ancestors
• The species could have arisen in Africa, but also
  possible that its lineage originated in Europe or
  Asia