Glossopteridales General Characteristics
Characteristics of Glossopteridales: Fossil Gymnosperm
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
General Characteristics of Glossopteridales
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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