Geology Reference
In-Depth Information
By the end of the Devonian Period, forests with tree-sized
plants up to 10 m tall had evolved. The Late Devonian
also witnessed the evolution of fl owerless seed plants
(gymnosperms) whose reproductive style freed them
from having to stay near water.
The Carboniferous Period was a time of vast coal
swamps, where conditions were ideal for the seedless
vascular plants. With the onset of more arid conditions
during the Permian, the gymnosperms became the domi-
nant element of the world's forests.
A major extinction occurred at the end of the Paleozoic
Era, affecting the invertebrates as well as the vertebrates.
Its cause is still the subject of debate.
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TABLE 21.4
Major Evolutionary and Geologic Events of the Paleozoic Era
Geologic
Period
Invertebrates
Vertebrates
Plants
Major Geologic Events
251
Largest mass extinction event
to affect the invertebrates
Acanthodians,
placoderms, and
pelycosaurs become
extinct
Therapsids and
pelycosaurs are the
most abundant reptiles
Formation of Pangaea
Gymnosperms diverse
and abundant
Permian
Alleghenian orogeny
Hercynian orogeny
299
Coal-forming swamps
common
Formation of Ancestral
Rockies
Continental glaciation
in Gondwana
Coal swamps with
fl ora of seedless
vascular plants and
gymnosperms
Amphibians abundant
and diverse
Fusulinids diversify
318
Reptiles evolve
Ouachita orogeny
Crinoids, lacy bryozans,
blastoids become abundant
Renewed adaptive radiation
following extinctions of many
reef-builders
Gymnosperms appear
(may have evolved
during Late Devonian)
Widespread deposition
of black shale
359
Extinctions of many reef-
building invertebrates near end
of Devonian
Reef building continues
Eurypterids abundant
Widespread deposition
of black shale
Acadian orogeny
Antler orogeny
Amphibians evolve
All major groups of fi sh
present—Age of Fish
First seeds evolve
Seedless vascular
plants diversify
Devonian
416
Major reef building
Diversity of invertebrates
remains high
Ostracoderms common
Acanthodians, the fi rst
jawed fi sh, fi sh evolve
Caledonian orogeny
Extensive barrier reefs
and evaporites
Early land plants—
seedless vascular
plants
Silurian
444
Extinctions of a variety of
marine invertebrates near end
of Ordovician
Major adaptive radiation of all
invertebrate groups
Suspension-feeders dominant
Plants move to land?
Continental glaciation
in Gondwana
Ordovician
Ostracoderms diversify
Taconic orogeny
488
Many trilobites become extinct
near end of Cambrian
Trilobites, brachiopods, and
archaeocyathids are most
abundant
Earliest vertebrates—
jawless fi sh called
ostracoderms
First Phanerozoic
transgression (Sauk)
onto North American
craton
Cambrian
542
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