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Major Evolutionary Faunas (Paleozoic Fauna Conditions (Food supplies more…
Major Evolutionary Faunas
3 Evolutionary Faunas
Cambrian Fauna
trilobites
monoplacophoran molluscs
inarticulate brachiopods
small shelly fauna
Dominant in Cambrian
Slow decline
&
disappeared hundreds Myr later
Paleozoic Fauna
Cephalopods
Echinoderms
Corals
Ostracods
More complex, more ecological
guilds
Stable Paleozoic diversity for ~200 Myr
Mass extinction ~End Devonian
Reefs hit hard
Huge End Permian Mass Extinction
Biggest mass extinction of all time
Nearly wiped out paleozoic fauna
Appeared Cambrian
Increasingly dominant
Ordivician
Stable
Paleozoic
Modern Fauna
bivalves
gastropods
echinoids
bony & cartilagenous fishes
Paleozoic Fauna Conditions
Continents more widely spaced
Food supplies more reliable
Plankton diverse and abundant in subdivided oceans
Benthic filter feeders more common & diverse
Free-swimming carnivores became more common & diverse
Cambrian Fauna Conditions
Continents not widely separated
Food supplies variable
One vast ocean
non diverse plankton
not much continental shelf
'mud grubbers'
Deposit feeding
in oceanfloor mud
= most reliable food source
Modern Fauna Conditions
New predator groups evolved
Easy targets = invertebrates:
with weak shells
attached to substrate & poor mobility
Groups with better defense mechanisms originate & proliferate