Life cycle of pteridosperms
Answers
Explanation:
HISTORY OF PALAEOZOIC FORESTS
PTERIDOSPERMS OR SEED FERNS
Pteridosperms or seed ferns are a very heterogeneous group of extinct plants with mostly fern-like foliage but with real seeds. They are mostly reconstructed as small trees but also forms with a climbing growth habit gave been found. Some forms, nobbly Medullosales, have really large fronds which could be up to 7 m long. Several groups can be distinguished within the pteridosperms. The classification of seed ferns is primarily based on fructifications and/or anatomical features. Eight groups of pteridosperms are presently recognised, six of them are known from the Palaeozoic and three from the Mesozoic. Some groups are very well known including their reproductive organs, whereas others are still very poorly understood and based on anatomically preserved vegetative remains, mostly axes.
Pteridosperms evolved in the latest Devonian (Fammenian) and became more common in the Carboniferous. The Lyginopteridales are most common in the Namurian and Lower Westphalian. The Medullosales took over the leading role during the Westphalian became less common in the latest Stephanian and persisted into the Permian. The small group of the Callistophytales is known from the Upper Westphalian to Lower Permian. Peltaspermales evolved in the late Stephanian and were most common in the Triassic. The essentially Permian Glossopteridales are typical Gondwana elements. Corystospermales and Caytoniales are Mesozoic pteridosperms