Cretaceous Period 2 Cretaceous Period 3 -...
Transcript of Cretaceous Period 2 Cretaceous Period 3 -...
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Primate Evolution
The fossil record of non-humanprimates
Cretaceous Period (135 - 65 m.y.a.)• Extremely active geological period
– Pangaea split into two segments by 125 m.y.a.• Northern land mass: Laurasia
– Included North America, Europe, Most of Asia– Rise of the Rocky Mountains
• Southern land mass: Gondwana– Included South America, Africa, Australia, Antarctica,
Indian subcontinent
– Worldwide climate much warmer than today sotropical and sub-tropical fossils are found farfrom the equator
Cretaceous Period 2• Floral Shift from gymnosperms to angiosperms
as dominant land plants– Gymnosperms are the vascular plants with seeds
that are not enclosed in an ovary (naked seeds),mainly the cone-bearing trees (ferns, ginkos,cycads, and conifers)
– Predominate from the Carboniferous period (about350 m.y.a.) when they began to displace the earliestspore-bearing land plants to the Cretaceous (about125 m.y.a.)
Cretaceous Period 3
– Angiosperms are the flowering plants, an advancedgroup of vascular plants with floral reproductivestructures and encapsulated seeds includingflowering herbs and trees, first appear near the endof the Mesozoic (135 m.y.a.)
• The flowering mechanism increased the potential forgenetic diversity (decreasing self pollination)
• Diversity of the angiosperms increased throughcoevolution with insect species, making for rapidadaptive radiation
Cretaceous Period 4
– During the Cretaceous angiosperms spread tobuild forests of increasing complexity, and tookover the dominant land plant role after the K/Textinction
– New econiches opened and old ones expanded• Frugivory: flowers and fruits are new food sources• Gramnivory: encased seeds from the new plants
• Insectivory: bugs that co-evolved with floweringspecies multiply increasing bug eating opportunities
Cretaceous/Tertiary Event
• Comet collisionrepresented by theChicxulub impact crateroff the north west coastof the Yucatan Peninsula– Combined effects of
terrestrial and marineimpact
– Dust and debris causecooling, break down offood webs
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K/T
• There is also a lot of volcanic activity on theDeccan Flats of the Indian subcontinent atthis time, adding to cooling
• > 50% of extant genera disappear at thistime– Terrestrial reptiles and marine invertebrates
most heavily affected– No land vertebrate larger than 50 pounds in
body weight survived the K/T
Primate Adaptation• Our Cretaceous ancestors were small, fuzzy
critters that were generalized enough in diet,morphology, and behavior to survive the K/Textinction
• Our primary adaptation at that time consisted ofthe “Good Luck” of being small, omnivorous,and behaviorally and ecologically flexible– Otherwise we would have gone the way of all large
bodied terrestrial vertebrates– This stochastic process appears to play a role in most
mass extinctions including the Permian and K/T
Epochs of the Tertiary Period,Cenozoic Era
Pleistocene 1.8 - 0.01 mya Ice Age
Pliocene 5 - 1.8 mya Hominid Radiation
Miocene 22.5 - 5 mya Hominoid Radiation
Oligocene 37 - 22.5 mya Anthropoid Origins
Eocene 53 - 37 mya First True Primates
Paleocene 65 - 53 mya Archonta Radiation
Paleoclimates
Whence come the Primates?
• Paleocene Placental Mammals:– No carnivores, rodents, modern herbivores– Primarily small, primitive insect eating animals
• Archonta (Superorder including Primates)– Plesiadapiformes: close relatives, possibly ancestral to
the Dermoptera (Colugo, Flying Lemurs)– Scandentia: Tree Shrews
– Chiroptera: Bats– Primates: Possibly including Purgatorius
Archonta
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Primate OriginsPrimate Family Tree
Living Critters
Anthropoid Origins
PaleoceneNon-Primate
Archonta
Scandentia(Tree Shrews)
Dermoptera(Flying Lemurs)
Chiroptera(Bats)
Plesiadapis rexfeeding on bugs in thetrees
Ignacius frugivorusfeeding on tree exudates
Picrodus silberlingifeeding on nectar in bushes
Chiromyoides minorfeeding on seeds
Mycrosyops elegansfeeding on bugs
Paleocene to Eocene Transition• Warming into the Eocene
– Warmest epoch of the Tertiary
• Wide ranging evergreen rain foreststhroughout North America and Europe
• Two cooling episodes broke the tropicality• From the mid-Eocene on there was a
gradual cooling and drying of the higherlatitudes
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EoceneContinentalConfigurationsand MigratoryPathways:A land bridgeconnected NorthAmerica and Europein the Early Eocenevia Iceland and theFaeroes and NorthAmerica and Asia viathe Bering Straight
Eocene Adaptations• First true Prosimians (Euprimates)• Primates spread with forested zones, appear to
adapt to preying on small, quick moving preyin arboreal settings (visual predation)– Grasping hands and feet– Nails instead of claws– Eyes rotated forward, enhanced stereoscopic vision– Elaboration of visual sensory pathways
Adapids versus Omomyids
Adapids,Omomyids, and
Anthropoids
Eocene to Oligocene Transition• Continued cooling, lowered sea level
– Extinction episode of many large bodied mammals atclose of Eocene
– Mid to high latitude vegetation changed dramaticallyfrom broadleaf evergreen rain forest to deciduousforests
• Remnant primates forced to cluster into smaller habitableforest areas near the equator (Fayum)
• Increased competition probably drove some changes inbehavior and adaptive patterns
– Habitats suitable for primates retreat into the currenttropics where most Oligocene primates are found
Paleoclimates
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Mid-Oligocene Extinction
• There is a mass faunal extinction event spanningabout 20,000 years at about 32 million years ago– Evident in the disappearance of archaic North
American land mammals• Potential Causes:
– Worldwide cooling and increased glaciation– Retreat of the Oceans– Floral changes related to Ocean circulation changes
• Catarrhines appear shortly after this extinctionEarly Oligoceneca. 35 m.y.a.
Apidium • 2-3 pounds• Arboreal quadruped• Fruit, seed eater• Very early and
primitive• Near split between
New World and OldWorld primates– Platyrrhine/Catarrhine
split
Aegyptopithecus
• 13 – 20 pounds (Howler monkey size)• Arboreal quadruped, slow climber• Frugivore, may have eaten some leaves• Very primitive, small brain, long snout• No derived characteristics of either
Cercopithecoids or Hominoids– May be close to the split between these groups
• Interesting degree of sexual dimorphism
Aegyptopithecuszeuxis
Propliopithecuschirobates
Apidiumphiomense
Origin of the Platyrrhini
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Origin of the PlatyrrhiniOligocene to Miocene Transition
• Warmer than the late Oligocene with highersea levels– Temperature peaks in mid-Miocene, about 15
m.y.a, then cools and climate becomes drier
• Continents were in nearly modern positions– Impact of India causes uplift in South Eurasia,
building Himalayan Mountains– African collision with Southwest Eurasia
causes rift valley system and allowed faunaldispersal
Miocene Fossil Ape Sites Miocene Hominoidea• Proconsulidae, early Miocene (Africa, Asia)
– Derived from Propliopithecids with larger bodiesand more modern molar morphology
– Proconsul• First Miocene ape described from Africa (1933)• 4 species ranging in size from 17 - 50 kg• Sexually dimorphic canines and frugivorous molars• Short limbs with monkey like proportions
– Quadrupedal and arboreal, but without suspensory abilitiesseen in living apes
• No tail-- like living apes
Juvenile Proconsul SkeletonJuvenileJuvenile ProconsulProconsul Miocene Hominoidea, 2
• Pongidae– Dryopithecus (mid to late Miocene, Europe)
• 20 - 35 kg, thin molar enamel, gracile canines, frugivore• Molar morphology is between Proconsuland Sivapithecus• Postcrania more like modern hominoids than that of any other
Miocene apes• Limbs suggest some suspensory ability
– Gigantopithecus (late Miocene to Pleistocene, Asia)• 2 species, 190 and 225 kg, largest known primate• Very thick mandible and broad molars, fibrous diet• Terrestrial locomotion?
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Dryopithecus Gigantopithecus
Miocene Hominoidea, 3
• Pongidae– Sivapithecus (late Miocene, Europe, Asia)
• 3 species from 40 - 90 kg• Thick molar enamel, low cusps, broad central incisors, seed
and nut eaters• Little canine dimorphism• Skull morphology very similar to living orangs—a likely
cousin• Quadrupedal rather than suspensory postcrania
– Ouranopithecus (late Miocene, Greece)• ca. 100 kg, Greek sites dated at 9 - 10 mya• Very thick molar enamel, relatively small canines• Wear analysis suggests a gritty diet like nuts or tubers• Facial morphology links to African apes and humans
Sivapithecus
Ouranopithecus Proconsulafricanus Dendropithecus
macinnesi
Limnopithecuslegetet
Proconsulnyanzae
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Ape AncestorsCatarrhine Cladogram
Molecular Clock