EVOLUTION OF FERNS

PTEROPHYTA EXTEND FROM THE LOWER DEVONIAN TO PRESENT TIMES

FOSSIL FERNS

     ORDER PROTOPTERIDALES

        PROTOPTERIDIUM

        WHEN LIVING: MIDDLE DEVONIAN

        WHERE: EASTERN CANADA, WESTERN
EUROPE AND CHINA

    CHARACTERISTICS:

       1.     SYMPODIAL AXIS
       2.     DICHOTOMOUSLY BRANCHED LATERAL APPENDAGES
       3.     SOME LATERAL APPENDAGES:
              a.     FLATTENED IN SMALL FRONDS
              b.     BEAR ELONGATE, STALKED SPORANGIA

      4.     SPORES SHED THROUGH A WELL DEFINED FISSURE
      5.     HOMOSPOROUS ??
      6.     CLOSELY RELATED TO THE PSILOTOPHYTA.

 ANEUROPHYTA

      WHEN:     MIDDLE DEVONIAN
      WHERE:    GERMANY AND NEW YORK
      CHARACTERISTICS:

         
1.     SHRUBBY PLANT
          2.     SEVERAL METERS TALL
          3.     BRANCHES BEAR EITHER:
                 a.     SMALL, DICHOTOMOUSLY
             
          BRANCHED STRUCTURES
TERMED
                       FRONDS
                 b.     FOOTBALL-SHAPED SPORANGIA
          4.     SPORANGIA ORIGINALLY THOUGHT TO BE SEEDS

ORDER CLADOXYLALES

     CLADOXYLON

     WHEN:     MIDDLE DEVONIAN INTO THE MISSISSIPPIAN

    
WHERE:     GERMANY, KENTUCKY,
NEW YORK

    
CHARACTERISTICS:

         
1.     IRREGULARLY DICHOTOMOUSLY-BRANCHED                    
                 STEM
          2.     STEM >2 CM IN DIAMETER
          3.     30 DM OR MORE TALL
          4.     BRANCHES BEAR:
                 a.     FLATTENED, DICHOTOMOUSLY FORKED
                        APPENDAGES (FRONDS)
                 b.     SMALL, OVOID SPORANGIA
          5.     SECONDARY XYLEM

     PSEUDOSPOROCHNES

     WHEN:     LOWER AND MIDDLE DEVONIAN

     CHARACTERISTICS:

         
1.     SMALL TREE, 1 METER HIGH
          2.     TERMINAL BRANCHES:
                 a.     BEAR FLATTENED, DICHOTOMOUSLY                         BRANCHED FRONDS
                 b.     BEAR SMALL, OVOID, PAIRED SPORANGIA

ORIGINALLY THOUGHT TO IN THE PSILOTOPHYTA DUE TO EXTERNAL MORPHOLOGY AND TERMINAL SPORANGIA

 

ORDER COENOPTERIDALES

    WHEN:    LATE DEVONION INTO THE PERMIUM

   CHARACTERISTICS: 

          1.     3-DIMENSIONAL FRONDS
          2.     SPHERICAL SPORANGIA BORNE ON TERMINAL OR
                    LATERAL BRANCHES
          3.     HETEROSPOROUS
          4.     MOST FERN-LIKE ANCESTOR OF MODERN FERNS

ORDER ARCHAEOPTERIDALES

     ARCHAEOPTERIS

    
WHEN:     UPPER DEVONIAN

    
WHERE:
   SYDNEY, NEW YORK

    
CHARACTERISTICS:

         
1.     TREE
          2.     SMALL LEAVES BORNE ON FLATTENED BRANCHES
          3.     ELONGATE SPORANGIA ON ULTIMATE BRANCHLETS

   
CALLIXYLON THOUGHT TO BE A GYMNOSPERM WAS REALLY
    ARCHAEOPTERIS

 

EVOLUTION WITHIN THE PTEROPHYTA

    ALL FOUR ORDERS ABOVE HAVE NO LIVING REPRESENTATIVES