Gondwana Flora and Fauna and its Importance | Geology Optional Notes for UPSC PDF Download

Gondwana Flora Summary

Gondwana and Gondwana Supergroup

• Gondwana refers to the southern part of the ancient supercontinent Pangaea.
• Pangaea existed around 510 to 180 million years ago before breaking into Gondwana and Laurasia.
• Laurasia comprised North America, Europe, and Asia, excluding India.
• Gondwana included South America, Africa, Antarctica, Australia, Madagascar, and the Indian subcontinent.
• The Gondwana Supergroup in India consists of sedimentary basins from the Upper Carboniferous to Lower Cretaceous periods.
• These basins are named after the Gond Kingdom in Central India.

Gondwana Basins in India

• The Gondwana basins in India cover an area of 50,000 sq. km.
• They are found along six linear belts: Damodar basin, Rewa basin, Wardha valley, Pranhita-Godavari basins, Mahanadi basin, and Rajmahal basin.

Classification Based on Plant Fossils

• The Gondwana Supergroup is divided into two groups based on plant fossils.
• The Lower Gondwana Group is known for the Glossopteris flora.
• The Upper Gondwana Group is characterized by the Dicroidium-Ptilophyllum flora.

Glossopteris Floral Phase of the Lower Gondwana Group

• The Gondwanan landmasses experienced icy conditions in the Late Carboniferous-Permian period, leading to sparse flora.
• Notable flora during this period included plants like Gangamopteris, Noeggerathiopsis, Plicatipollenites, and Potoniciporites.
• Characteristics of the plants included small-sized leaves with fine venation and a lack of a mid-rib, as seen in Gangamopteris.
• With the retreat of glaciers by the Permian era, both land and higher temperatures became conducive for plant growth.
• Examples like Gangamopteris showed significant growth, with leaves recorded up to 8 cm in length.
• The appearance of conifer-like Paranacladus and the diversification of plant species marked this period.
• Further into the Permian era, Gangamopteris leaves grew as long as 35 cm and 8 cm wide, showcasing plant diversification.
• Lower Permian deposits reported around 14 species of Gangamopteris and 11 of Noeggerahiopsis.
• New species such as Gymnosperms like Buriadia and ferns emerged during this time.
• Gangamopteris eventually declined, paving the way for the dominance of Glossopteris in the ecosystem.

Glossopteris and Triassic Flora Overview

• Glossopteris in Lower Gondwana

  • During the Late Permian period, Glossopteris emerged as a significant plant in Gondwanaland.
  • Characterized by large leaves, approximately 60 cm long, 15 cm wide, and with a thick petiole of 1.5 cm.
  • Leaves featured a mid-rib and reticulate venation.
  • About 70 different species of Glossopteris thrived on the ancient Gondwanan landmasses.

• Transition to Triassic

  • During the Triassic period, Glossopteris persisted but declined due to a shift in climate towards semi-arid conditions.
  • Thinfeldia, also known as Dicroidium, replaced Glossopteris as the dominant flora.
  • Other plants like Lepidopteris, Cycadopteris, and Neocalamites adapted to semi-arid environments.
  • With improving conditions in the upper Triassic, species like Pterophyllum, Taeniopteris, and Pseudopteris emerged.

• Flora Diversity in Triassic

  • Conifers such as Podozamites and Araucarites, ferns like Cladophlebis and Parsoraphyllum, as well as Ginkgo and Baiera were present.
  • Two proposed categorizations: Thinfeldia floral phase for the Middle Gondwana and Glossopteris floral phase for the Lower Gondwana.

Ptilophyllum Floral Phase of the Upper Gondwana

• Jurassic Time Period:

  During the Jurassic era, the Gondwana landmasses started to break apart. The climate transitioned from warm and humid to temperate and seasonal.

• Dominant Flora:

  The Ptilophyllum floral phase was characterized by the prevalence of various plant species including Ptilophyllum, Equisetales, filicales, pteridosperms, cycadophytes, coniferales, and ginkgoales across the Gondwana region.

• Evolution of Flora:

  Initially, during the Early to Middle Jurassic period, cycads and ferns such as Marattiaceae and Osmundaceae thrived in warm and moist environments.

  As the Late Jurassic to Early Cretaceous period approached, conifers and ginkophytes like Ginkgoites and Brachyphyllum became more prevalent due to the shift to a seasonal climate with hot and wet summers and cold and dry winters.

• Fern Diversity:

  Although ferns like Polydiaceae and Onychiopsis existed during this time, they were relatively rare compared to other plant species.

• Significance of Ptilophyllum:

  Due to the dominance of Ptilophyllum flora, this era is referred to as the Ptilophyllum floral phase, which represents the upper portion of the Gondwana region.