Monday, 24 May 2021

The Mississipian and Pennsylvanian periods are together

 The Mississipian and Pennsylvanian periods are together



Named so after Devon city in England where rocks of that period was first discovered. The fossils of Psilopsids, Tycopsids, Sphenopsids, ferns, Liverworts, Horse tails, Pterospermales etc. were discovered from rock sediments of this period. (v) Mississipian Period : This is a period of Palaeozoic era. It is named after the city Mississipi. It lasted for 25 million years. Coal beds were discovered. The fossils of tree-like Lycopods were discovered from rock of that age.

 (vi) Pennsylvanian Period : It is a period of Palaeozoic era. This period was named after the city Pennsylvania. It lasted for 25 years. The Mississipian and Pennsylvanian periods are together called Carboniferous period. The fossils of mosses, cordaitals and Pteridospermales were predominant in the rocks of that age.

 (vii) Permian Period : It is a period of Palaeozoic era. This period lasted for 30 million years. The fossils of Ginkgoales and primitive coniferales were discovered from rock deposits of this period. 5. Mesozoic Era The mesozoic era is the period of 'middle life', It started 225 million years ago and ended 75 million years back.

 Cycads had flourished well in that era, so that it is called 'age of cycads'. The supporters of this view consider that the similarity in the sex organs and life-cycles of bryophytes and pteridophytes is due to their parallel evolution. Campbell (1895), Lignier (1903), Zimmermand (1930, 1938), and Bower (1935), on the other band nostulated that ancestors of pteridophytes were some.

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