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)