EARLY PALEOZOIC
 
Cambrian, Ordovician, Silurian
    190,000,000 yrs. total time
*On most continents
    Gradual marine invasions of the low lying interior
       * Cratonic sequence
    Wide expanse of shallow epicontinental seas
     Moderated climate - wide variety of marine organisms
*Long periods of sedimentation punctuated by severe change involving earth movements
    and mountain building
*Supercontinent together at beginning of Paleozoic
    Very early Cambrian Pangea I begins to break up
    Before close of Cambrian wide enough to admit seas
    *Elongate tracts become collecting troughs for sediments
        Now are mountain ranges - Appalachian, Urals, northwest Europe highlands
 
 
Simplified Paleozoic Model
 
 
Early Paleozoic
 

1.    Begin Cambrian continents begin joined
2.    Late Cambrian-Early Ordovician
            Split into 4 continents
3.    Late Ordovician - Europe-North America joined - Taconic orogeny
4.    Silurian - Caledonian orogeny
 
 

Late Paleozoic
 
 
5.    Devonian-            *Appalachian orogeny
       Pennsylvanian
6.    Permian - Asia-Euroamerica-Gondwanaland joined
            *Pangea II formed
 
 
Cratons and Mobile Belts
 
 
Cratons
    Form ancient continental nuclei of continental landmasses
        Most shields stable throughout Paleozoic
    Stable platform
        Sedimentary veneer over pC rocks
Mobile belts
    North American craton bounded on all sides by great elongate tracts
    *Sites of geosynclines, intense deformation, igneous activity
    *Mobile belts - one or more present on all continents
 
 
Early Paleozoic Events
 
 
Beginning - relatively quiet time for North America
    Tranquility after Late pC orogenies
Oceans invade continents - cratonic sequences
    Several episodes of marine transgressions
*Advances and retreats of epicontinental seas most dominant event in Early Paleozoic history of
continental interiors

Geosynclines
    Western geosyncline - Cordilleran
    Franklinian geosyncline - northern margins of continent
    Appalachian geosyncline - Early Paleozoic is deposition phase of Appalachians
 
 

Early Paleozoic Life
 
Early Paleozoic - Cambrian - marine invertebrates
     Shallow seas filled with invertebrates
     Trilobites, brachiopods
Invertebrate Animals
 
Cambrian and Ordivician
 
Diversity of marine invertebrates - adaptive radiation

1.  Sponges
        Stationary
        Highly perforated vase modified by folds and canals
        Stromatoporoids -  reef building algae

2.  Corals and coelenterates

     Sea anemones, sea fans, jellyfish and reef building corals - coelenterata
     Outer layer of cells
     Presence of stinging cells
     Jellyfish impressions - late Precambrian
     Plentiful by Ordivician

3.  Bryozoans - moss animals

     Minute bilaterally symmetric animals
     Early Ordivician
     Contribute to framework of reefs
     Stratigraphic correlation
     Today 4,000 living species

4.  Brachiopods

     2nd only to trilobites
     Abundant, diverse, and useful Early Paleozoic organism
     Symmetrical on either side of mid-line
     Still alive today - reduced numbers

5.  Mollusks

     Common on seashores
     Most possess shells
     Well developed organs
          Digestive, sensory, circulation - advanced
     Pelecypods - clams, oysters, mussels
          Layered gills
     Gastropods
          Coiled shells
     Cephalopods
        - most complex of mollusks
          Squid, octopus, nautilus
          Coils in a plane

6.  Arthropods - enormous classification

     Lobsters, spiders, insects, trilobites
     Exterior skeletons. jointed bodies, nervous system
     Trilobites - swimming or crawling arthropods
          Growth by molting
          Abundant Cambrian
          Extinct in Late Paleozoic
          Guide fossil
     Eurypterids - scorpion-like creature - 9 ft. long!

7.  Echinodermata - spiny skinned animals
         Marine, bottom-dwelling
         Evolutionary relationship between echinoderms and vertebrates
 

Vertebrates

First fish in Ordivician
     Jawless fish
Followed shortly by shark-like fish
 

Later armor-plated fish
     Latimeria - living coelacanth
 
Colonization of the Land

Obscure bacteria and algae - Precambrian
Stromatolites - algae, laminations
     Widespread Cambrian
Begin Paleozoic - continents devoid of life
     No forests, no grasses
Most living things confined to oceans
Plants are basic O2 supply
      Basic energy source for food
     Must have preceded animals on land
By Silurian times, 440.000,000 B.P.
     First land-plant fossils
     Green algae from bays and swamps
     Most land plants are vascular
     Tiny tubes to transport fluids and nutrients
Psilophytes - Upper Silurian
      Simple vascular tissue
After initial appearance of land plant fossils, rapid growth of plant community
     Devonian period
     Ferns, trees, reeds
     Later become luxuriant swamp forests - coal forests
 
 
 

Late Paleozoic Life
Devovian
 
Crawling ashore shortly after first land plants - arthropods

Forests - energy supply for insects
     No competition
     Resource is exploited
     Insects evolve into hundreds of forms
Huge - roaches with 10 in. long, dragonfly with 2 ft. wingspan
Widespread colonization of the land by both land plants and vertebrates
     Amphibians, reptiles, spore-bearing trees - later conifers

Where there is a food supply something will eat it!
     Fish eat insect larvae
     Dry season - water levels drop in ponds and rivers
     Some fish survive - lobefin fish
     Crossopterygii

First amphibians in Devonian

Late Paleozoic Amphibians - Cacapos
 
 

 

     400,000,000 B.P.
     Can live on land, but have to lay eggs in the water
     Tied to the water
     Experienced a short period of dominance on the land
     Not common today - frogs, toads, and salamanders
     Failed because
      Skin - needs moist environment or dries out
      Reproductive system
       Tied to the water
       Lower survival rate
 
 
Carboniferous
(Mississippian and Pennsylvanian)
Vast coal deposits form
First primitive reptile appears during the Pennsylvanian - 300,000,000 B.P.

 Represent a major advance
 Well-adapted to life on the land
 Looked like amphibians, but had a major advantage
     Amniotic egg!
 

Amniotic Egg
 

 

     Amphibian egg was a jelly-like substance which had to be left in the
     water
     Egg of reptile was a major advance
     Contained own food supply
     Protective covering
     Able to exchange CO2  for O2
Freed reptile from the water
     Allowed for much greater freedom on the land
      Reptiles do not have to return to the water for reproduction
      Higher survival rate of the young
Therapsid - mammal like reptile at end of the Permian
 
  
Therapsid