Lepidodendrales †

Scale Trees

This group formed some of the first swamps on Earth. These trees grew to over 100 feet, and over 5 feet in diameter (similar to a large oak tree). These trees differed from modern trees, such that they were constructed with a small amount of wood, and large amounts of bark. This made the trees less stable than modern plants, and prone to falling over after a few years of maturity. This created large amounts of plant debris on the swamp floor, which piled up over years. This large amount of biomass became the coal that we use as fossil fuels today.

Age: Devonian - Permian

  • Ecology and Form
    • Arborescence in extinct taxa 
    • Inhabited late Paleozoic swamps
  • Stems (e.gLepidodendron, Sigillaria, Diaphorodendron)
    • Pseudo-bipolar growth
      • Root decays early in development
      • Early embryonic shoot splits with one "branch" becoming the "root" or rhizophore
    • Exarch primary growth
    • Unifacial (one-faced) cambium
      • Small amount of secondary xylem (wood)
      • No secondary phloem
        • Sugars from photosynthesis could not be transported to rhizophore
    • Large amount of bark (phellem) 
      • major support structure
  • Leaves (Lepidophylloides)
    • Microphylls or lycophylls
      • very long; up to 14" long
    • Spiral phyllotaxy shown in leaf scars on bark
  • Roots
    • No true roots
    • Rhizome-like stem called rhizophore (Stigmaria) acts like roots
    • Modified leaves acts like secondary roots to absorb water minerals
      • Rhizophore has rhizotaxis (pattern of root insertion) due to leaves growing in an apical fashion
  • Reproductive Structures
    • Sporangia in cones (Lepidosporobus)
    • Heterosporous
      • Megaspores and microspores
    • Endosporic development
      • Female gametophyte is not free-living
      • Seed-like
    • Possibly monocarpic (reproduce once and then die)
Superkingdom Archaeplastida - plants + algal relatives
   Kingdom Plantae - "plants"
      Subkingdom Embryophyta - land plants
         Phylum Lycopodiophyta- club-mosses and their allies
            Class Lycopsida
               Order Lepidodendrales
                   Family Lepidodendraceae 
      • intrafoliar parichnos that extend below the leaf scar
      • dorsiventrally-flattened megaspore with distal dehiscence
                   Family Diaphorodendraceae 
      • medullated protostele
      • dorsiventrally-flattened megaspore with proximal dehiscence
                   Family Sigillariaceae 

  • Diaphorodendron: 
  • Sigillaria: upright stem with bark
  • Lepidodendron: upright stem with bark
  • Lepidophylloides: leaves (microphylls) 
  • Stigmaria: root-like rhizophore (modified rhizome-like stem that anchors and absorbs water/minerals)
  • Lepidostrobophyllum: sporophyll (leaf protecting sporangia)
  • Lepidocarpon: female cone (contains megaspores) 
  • Cystosporites: megaspores, which will produce female gametophytes
  • Lepidostrobus: male cones (contains microspores) 
  • Lycospora: microspore, which will produce male gametophytes
Additional Resources