Ordovician

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Ordovician

• The first vertebrates - jawless fishes called
  ostracoderms

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Ordovician

• Reef-forming corals called rugose corals

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Ordovician

• Eurypterids or sea scorpions - up to 2 m long

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Ordovician

• Major radiation of trilobites and brachiopods

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Ordovician mass extinction

• Occurred at the end of the Ordovician
• Second largest mass extinction, especially for
  marine animals
• Apparently caused by movements of southern
  continents toward the South Pole
• Cooler climate caused more tropical species to go
  extinct
• Water tied up in glaciers caused sea level to
  fall

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Silurian

• First land animals (millipedes, centipedes,
  arachnids)

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Silurian

• First jawed fishes (placoderms)

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Silurian

• Appearance of first higher plant, Cooksonia
• This plant had neither leaves nor roots
• Its stem projected 10 cm high from which spores
  were released for dispersal

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Devonian

• First insects (both winged and wingless species)

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Devonian

• First trees and first forests

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Devonian

• Explosive radiation of modern fishes
• Associated with extinction of many jawless fishes
• Two major groups
• Ray-finned fishes (Actinopterygii)
• Lobe-finned fishes (Sarcopterygii)
• The pectoral and pelvic fins of the lobe-finned
  fishes had fleshy central portions unlike the
  ray-finned fishes

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Devonian

• First sharks

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Ray-finned fish
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Coelacanths
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Coelacanth distribution
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Lungfishes
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How to make a leg out of a fin

• A sarcopterygian fin is made up of preaxial,
  axial and postaxial elements
• To make a leg of a fin, the axis of the limb has
  to curve around
• Some of the preaxials were incorporated into arm
  and wrist
• The postaxials end up as the digits

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Acanthostega - amphibian but probably fully
aquatic
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Devonian

• First land amphibians (Ichthyostega)

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Devonian mass extinction

• At end of Devonian
• Primarily affected marine organisms
• Rugosan corals, brachiopods, trilobites, jawless
  fishes and placoderms greatly affected
• About 60 of existing species went extinct
• What was the cause?
• Most species affected were warm water forms,
  suggesting that global cooling might have been
  responsible

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Carboniferous

• Climate was warm and humid
• Extensive coal-forming swamps

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Carboniferous

• Dragonflies with 70 cm wing spans (Meganeura)
• Millipedes over 2 m long

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Carboniferous

• Extensive radiation of amphibians
• Bewildering diversity
• Two groups evolved of great importance
• Lissamphibia - gave rise to living amphibians
• Anthracosaurs - gave rise to reptiles, birds and
  mammals

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Anthracosaurs
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Carboniferous

• First reptiles (amniotic or cleidoic egg)