Pteridospermales (Cycadofilicales): An Overview

The Pteridospermales or Cycadofilicales are characteristic gymnospermous plants that bore fern-like foliage, which in turn bore seeds that were unprotected. Hence, they are known as seed ferns.

Pteridospermales is a very large order that includes a heterogeneous assemblage of tree-like organisms. The plants lived through the Carboniferous period, reached their climax, and became extinct in the Jurassic period of the Mesozoic era.

Pteridospermales or Cycadofilicales

Characteristics of Pteridospermales

  • Plants possessed erect, slender, or weak stems with large frond-like leaves.
  • Primary xylem was in the form of a solid or medullated protostele and was usually mesarch, rarely exarch.
  • Secondary wood was monoxylic.
  • Tracheids of secondary wood had multiseriate-bordered pits on their radial walls.
  • The leaves were large, fern-like, and pinnately compound. They were arranged spirally at the apex of the stem.
  • The leaves of all types were covered by a resistant cuticle.
  • Microsporangia were exanulate and, sometimes, grouped into synangia.
  • Megasporophyll were like foliage leaves.
  • The integument was vascularized.
  • The nucellus was also vascularized in some ovules.
  • No pollen tubes were present in the pollen grains.
  • The pollen grains (megaspores) may be monolete or trilete.
  • Megaspore was surrounded by a thick wall.
  • The seeds were not borne on inflorescence or cones.
  • Seeds had a considerable resemblance to those of present-day cycads.
Figure: Life restoration of Lepidopteris. Image Source: Wikimedia Commons

Classification of Pteridospermales

Arnold (1948) divided Pteridospermales into three families. Viz-

  1. Lyginopteridaceae
  2. Medullosaceae
  3. Calamopityaceae

Sporne (1974) divided it into the following seven families:

  1. Lyginopteridaceae
  2. Medullosaceae
  3. Calamopityaceae
  4. Glossopteridaceae
  5. Peltaspermaceae
  6. Corystospermaceae
  7. Caytoniaceae
Animesh Sahoo
Animesh Sahoo

Animesh Sahoo is a scientific blogger who is passionate about biology, nature, and living organisms. He enjoys sharing his knowledge through his writings. During his free time, Animesh likes to try new activities, go on adventures, experiment with different biological aspects, and learn about various organisms.

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