Vertebrates
Sharks
Bony
fish
Lampreys
Coelacanth
Land
vertebrates
Hagfish
Cladogram of vertebrates, stressing early forms from UC Berkeley Museum of Paleontology
Vertebrate characters
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Cranium – brain case
Vertebrae (spinal
protection of cartilage
or bone) – almost all
* agility
* speed
No larval stages
Evolved during
Cambrian (early
Paleozoic)
Myllokunmingia fossil from
SE China, -530 my
Trends in vertebrate evolution
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improvements in vertebral column – cartilage,
bone
gill slit supports – jaws, other head bones
appendages – fins, legs, wings
respiration – gills & lungs
circulation – heart
reproduction – eggs, shells, “live” young
existing (& some extinct) classes trace some of
the most important advances along the vertebrate
evolutionary path – next slides follow these
No Jaws
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Hagfish
* cartilage
* partial cranium
* slime a defense
mechanism
Lampreys
* cartilage
* full cranium
* fish parasites &
free living
hagfish tie themselves into
knots to clean themselves
Jaws
• evolved from gill arches
• later bore teeth
• mid Paleozoic (Silurian) origin
recent Swedish shark
Dunkleosteus Devonian
(mid Paleozoic) Placoderm
Carcharodon megalodon
Miocene (Cenozoic) shark
Jaws II
1m
Jaws III
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also:
* articulated cranium &
spine
* appendages (fins) some paired
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modern day
Cartilaginous Fish
* sharks, rays, etc.
* no swim bladder –
must swim to “levitate”
Manta Ray
Bone
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Bony fish = ray-finned
fish
* also bony scales
* most numerous &
diverse vertebrate
* lungfish have “lungs”
• gut pockets
• modified circulation
Legs
• Amphibians
* the mosses of the animal
world
* limbs supported by bones
• support
• movement
* articulated to “girdles”
• connections to spines
• hips and shoulder
* but amphibians tied to water:
• at least eggs (shell-less)
• & larval stages
young Rough-skinned Newt
Legs II
• more on Amphibians
* land life advantages
• more oxygen
• prey – arthropods & plants
• fewer (no?) predators
Northwest Tailed Frog
* sound / sight / balance improvements
(terrestrial sensors)
• ears and eyes
* first amphibians: Devonian (mid
Paleozoic)
Shelled eggs
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Reptiles
* amniote eggs with:
• extra-embryonic
membranes
• shells for protection
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dry scaly skin
internal fertilization
adult care for young
kidneys conserve water
Reptiles II
• Evolved in late Paleozoic (Carboniferous)
• Huge diversity – polyphyletic with many
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long-lived lines from the end of the
Paleozoic
Two early lines
* Sauropsids – most of the diverse lines
* Synapsids – ultimately gave rise to mammals
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Birds
Just another reptilian group?
Feathers – insulating, flight (modified scales)
Bones hollow
Beaks
Thermoregulation – high metabolism rates
All adaptations for flight
Patterns of behavior
* Elaborate mating behavior
* Maternal/paternal care
* Migration
Birds II
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Evolved from
theropod dinosaurs,
mid Mesozoic
Archaeopteryx lithographica 150 my
Birds III
Sinosauropteryx prima 125 my
Caudipteryx zoui 125 my
Mammals I
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Hair (modified scales)
Milk fed to young
Live young (except for 3 that lay eggs)
Precise teeth that fit together
3 middle ear bones (derived from jaw
bones)
Mammals II
• Three major lines
* monotremes – egg layers
* marsupials – pouched
* eutherian – placental
Spiny echidna, egg-layer
Marsupial “mouse”
Blue whale, largest mammal
Mammals IIIA
• Evolved in early Paleozoic 200 mya
• Adaptive radiation during mesozoic &
cenozoic tied to continental drift – see ST
Fig 26.2
* End of mesozoic opened habitats
* Mammals much more efficient terrestrial forms
• Drifting continents isolated mammalian
groups on “rafts”
Mammals IIIB
Early Triassic
Late Triassic
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Early Cretaceous
Late Cretaceous
• Compare with ST Fig 26.2
Mammals IIIC
Modern day mammalian distribution
Mammals IV - Primates
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3 present groups
Galago
* prosimians – lemurs, galagos
* tarsiers
* monkeys, apes, humans
Early primates evolved in early
Cenozoic from rodent ancestors
5 features preadapted early
primates to modify later in the line
toward humans
* enhanced vision
* upright walking
* modifications in hand bones &
muscles
* generalized teeth
* social behavior (& increases in brain
capacity and complexity)
Barbary Macaque
Tarsier
Human evolution
• Humans evolved in Africa
• Earliest huminoids – mid Cenozoic (25 mya)
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* cooler climate led to challenges
* later radiation of “southern apes” (Australopithecus) 4-3 mya
* first appearance of Homo ~ 2.5 mya
Homo erectus leaves Africa ~2 mya
Homo sapiens evolved 150,000 ya
Homo neanderthalensis evolved 250,000 ya; extinct 35,000
Recent studies show no DNA mixing or carryover of H. n. DNA in
modern human lines
Most evidence supports Out of Africa theory rather than
multiregionalism
• Best site for current status of human evolution facts:
http://www.talkorigins.org/faqs/homs/
Human evolution timeline
Chart from: http://www.talkorigins.org/faqs/homs/species.html
Interactive Human Evolution