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The Paleozoic Era!
Time for BIG changes!
Geologists divided the later strata into 3 major groups
Paleozoic Era
Mesozoic Era
Cenozoic Era
Remember this?
Ediacaran
4 billion years of Earth history!
We will explore the Paleozoic first…
Modern era
About 550 million years ago
Dinosaurs!
Ice Age
The more recent layers are subdivided into “PERIODS”
Paleozoic Era
Permian
Pennsylvanian
Mississippian
Devonian
Silurian
Ordovician
Cambrian
Ediacaran
Brachiopods, Molluscs
Bi-valves, Arthropods
Trilobites
A more diverse community is present!
The Early Paleozoic… Many new life forms with HARD SHELLS evolve…
A typical scene in the early Paleozoic Era.
Cephalopod
Trilobite
Crinoid
Brachiopod
Coral
Perm
Penn
Miss
Dev
Sil
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From earlier animals with a “hint” of a backbone…
There evolved the first vertebrates!
By the early Cambrian…
…the first Fish swam the seas.
OrdovicianNew species continue to evolve… others become extinct…
Perm
Penn
Miss
Dev
Sil
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Cam
SilurianNew species continue to evolve… others become extinct…
Perm
Penn
Miss
Dev
Sil
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But…big changes are occurring!
Starting possibly as early as the later Ordovician…
(Probable SPORES have been found)
…land plants had been evolving!
Perm
Penn
Miss
Dev
Sil
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Cam
By the middle Silurian…
Early land plants looked like this…
…but the REALLY big story is elsewhere.
By the start of the Devonian…
Near the shore, or in and along streams and coastal swamps, a major invasion is taking place…
The ocean is filled with life…
Early Devonian landscapeZ. Burian (In: Špinar & Burian, 1972);
Fossil stumps…
…and leaves…
…indicate that plant life had moved ashore!
And by the end of the Devonian…
…the first real forests grew.
Perm
Penn
Miss
Dev
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Archaeopteris dominates
THAT produced major changes in the landscape!
Earlier vegetation lacked the root systems of present-day vegetation…
Those plants also produced little shade or leaf litter.
…plants were apparently restricted to being near water
The evolution of new types of trees lead to a richer environment, creating more organic material…
…and probably changed stream channel morphology, and altered erosion and deposition.
Braided Streams
Overwhelming amounts of eroded material
Meandering Streams
DevonianAs always, new species continue to evolve, and other species become extinct…
Perm
Penn
Miss
Dev
Sil
Ord
Cam
Which sometimes seems like you’re watching the same play over and over with different actors!
The first Fish evolved near the start of the Early Paleozoic…
Early Fish
…but these more minor changes are overshadowed by MAJOR developments!
Later…Armored Fish evolved! (Placoderms)
Some are small…
… Some reach AWESOME size!
I wish he’d be more careful!
Why would some fish evolve armor?
Why would they then become extinct?
And…perhaps, near those new forests…
Some fish evolve sturdy fins that may help them move through shallow water.
It proves to be a successful change
But what is this…?
This is a Fish…
They are part of a series of fossils that show the transition from a “water animal”: a fish…
…to animals that are at least partially terrestrial!
Eusthenopteron
Pandericthyes
Tiktaalik
Acanthostega
Icthyostega
The newest find: Tiktaalik!
Note Tiktaalik!
Obvious Fish!
Obvious Amphibian!
Transitional Forms
So…during the early Paleozoic…
The FIRST LAND PLANTS appear…
And at the end…a branch of fish evolve sturdy limbs and become the first AMPHIBIANS.
Hard shell animals evolve…
Trilobites, brachiopods, corals, cephalopods “rule the seas”
FISH EVOLVE…Armored fish evolve… …and then fade away.
…but before the end of the Paleozoic… new creatures evolved.
The late Paleozoic …
Amphibians had already moved ashore and taken over…
…and the first forests already existed…
In the oceans, new species continue to evolve…
Perm
Penn
Miss
Dev
Sil
Ord
Cam
Mississippian
PennsylvanianBut the action is NOT all in the ocean anymore!
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…by the Pennsylvanian, a vast diversity of plant life had evolved…
Some of which now towered as much as 100 feet over the land…
the land was covered by new species of plants.
Perm
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Miss
Dev
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The Illinois Coal Forest: a great river delta where buried trees became coal.
…this is the time that great forests covered much of Illinois!
The “Tully Monster”!
It’s also the time of the Illinois State Fossil…
During the Later Paleozoic, amphibians evolved into reptiles…
With hard-shelled eggs, Reptiles were “freed” from water…
…and reptiles evolved into many different types.
This diagram shows the transitional change in the jawbones from ancient Reptiles to early Mammals.
Early Reptiles
Early Mammals
Near the end of the Paleozoic, as this evolutionary sequence continued…
…Mammal-like Reptiles appear.
Mammal-like Reptiles are reptiles with Mammal-like features.
(Obviously! : )
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Miss
Dev
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They do NOT look like “typical” reptiles.
They aren’t quite mammals, either…
…but one group WILL be!
But before this happens…
There is an enormous change: The “MOTHER of ALL EXTINCTIONS!”
For the Trilobites…
For Brachiopods…
it’s the end!
it’s never the same!
Perm
Penn
Miss
Dev
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…almost a total wipeout!
For other groups: extinction of many species!
…and for the Mammal-Like Reptiles…
Perm
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In the later Paleozoic…
Amphibians “ruled”…for a while
Insects filled the land…
Great forests covered the land… the “Coal Age” in Illinois
Reptiles evolved from Amphibians
Mammal-like Reptiles evolved…
…and then much was lost in the
“Great Extinction” at the end of the Paleozoic.
On to…
(Watch out for Dinosaurs!)
The MESOZOIC!
Same color = same bones
Notice the transitional changes from Eusthenopteron to Ichthyostega
Eusthenopteron
Ichthyostega
…life had moved from the ocean to the land…
Remember: in the Early Paleozoic…
The first land plants had evolved…
The first insects roamed the land…
And the first amphibians were evolving…
