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Ordovician
The first vertebrates - jawless fishes called ostracoderms
Ordovician
Reef-forming corals called rugose corals
Ordovician
Eurypterids or sea scorpions - up to 2 m long
OrdovicianMajor radiation of trilobites and brachiopods
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
Silurian
First land animals (millipedes, centipedes, arachnids)
SilurianFirst jawed fishes (placoderms)
Silurian
Appearance of first higher plant, CooksoniaThis plant had neither leaves nor roots
Its stem projected 10 cm high from which spores were released for dispersal
Devonian
First insects (both winged and wingless species)
Devonian
First trees and first forests
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
Devonian
First sharks
Ray-finned fish
Coelacanths
Coelacanth distribution
Lungfishes
How to make a leg out of a fin
A sarcopterygian fin is made up of preaxial, axial and postaxial elementsTo make a leg of a fin, the axis of the limb has to curve aroundSome of the preaxials were incorporated into arm and wristThe postaxials end up as the digits
Acanthostega - amphibian but probably fully aquatic
Devonian
First land amphibians (Ichthyostega)
Devonian mass extinctionAt end of Devonian
Primarily affected marine organismsRugosan 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
Carboniferous
Climate was warm and humid
Extensive coal-forming swamps
Carboniferous
Dragonflies with 70 cm wing spans (Meganeura)
Millipedes over 2 m long
Carboniferous
Extensive radiation of amphibians
Bewildering diversity
Two groups evolved of great importanceLissamphibia - gave rise to living amphibians
Anthracosaurs - gave rise to reptiles, birds and mammals
Anthracosaurs
Carboniferous
First reptiles (amniotic or cleidoic egg)