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

Ordovician Major 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)

Silurian First jawed fishes (placoderms)

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

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 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

Acanthostega - amphibian but probably fully aquatic

Devonian First land amphibians (Ichthyostega)

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

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 importance Lissamphibia - gave rise to living amphibians Anthracosaurs - gave rise to reptiles, birds and mammals

Anthracosaurs

Carboniferous First reptiles (amniotic or cleidoic egg)