Glossopteridales and Glossopteris- General Characteristics

Glossopteridales and Glossopteris

Ø  Glossopteridales included an extinct group of seed plants (Gymnosperms).

Ø  They were originated during the Permian period on the Gondwana Continent.

Ø  They became the dominant vegetation in the Permian period.

Ø  They extinct completely by the end of the Triassic period.

Ø  The order name derived from the genus Glossopteris

Ø  Glossopteris is the best-known member of Glossopteridales

Ø  Glossopteris is a leaf.

Ø  The name ‘Glossopteris’ means ‘tongue-fern’.

Ø  The name was used to describe fossil leaves from India and Australia that were spatulate and tongue-shaped (Glossa = tongue)

Ø  About 70 species of Glossopteris have been recognized from India alone.

Ø  Glossopteris was also reported from South America, Australia, Africa, and Antarctica.

Important Genera of Glossopteridales

Ø  Leaves: Glossopteris, Gangamopteris

Ø  Stem and Root: Vertebraria

Ø  Male Fructification: Glossotheca

Ø  Female Fructifications – Two types:

(1). Cupular fructifications: Pterigospermum

(2). Multi-ovulate fructifications: Scutum

Glossopteridales Characteristics

Ø  A small to medium-sized highly branched tree.

Ø  Leaves were dorsiventral.

Ø  Leaf lamina was flat in the dorsal side.

Ø  Venations were reticulate.

Ø  Veins were parallel but anastomosing.

Ø  Lateral veins originated from the midrib.

Ø  Midribs were with tracheids of scalariform or pitted thickening.

Ø  In the ventral side of the leaf, the midrib and veins were raised.

Ø  Mesophyll was differentiated into palisade and spongy tissues.

Ø  Stomata were present on the lower surface of the leaf.

Ø  The stomata were haplocheilic type.

Ø  Stomata present between the veins.

Ø  Stomata were sunken type, indicate xerophytic adaptation.

Ø  Stomatal subsidiary cells were papillate.

Ø  Hairs or trichomes may be present on the leaves.

Ø  The hairs may be branched or unbranched.

Ø  Fructifications of the Glossopteridales poorly preserved in fossils.

Ø  Reproductive structures were unusual as the foliage leaves.

Ø  Reproductive structures were born on the leaves as in “Pteridospermales“.

Learn more: General Characteristics of Pteridospermales

Ø  Pollen and seeds were produced on separate leaves. This indicates unisexual strobilus.

Ø  Pollen grains were produced inside the sporangia

Ø  Sporangia were formed on modified leaves called sporophylls.

Ø  Each sporangium bear staked pollen sacks.

Ø  Ovulate bearing organs are more preserved in fossil than pollen.

Ø  Female strictures were very diverse indicating a wide diversity among this group.

Ø  Seeds were produced on the under surface of the leaves.

Ø  Leaf edges rolled over to form an enclosing structure to protect the seeds.

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