Phylum Progymnosperms

by Hango
Last updated 8 years ago

Discipline:
Science
Subject:
Biology

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Phylum Progymnosperms

Progymnospermsearliest fossils of gymnosperms are about 305 million yrs old

"an ancestral fossil type from which modern gymnosperms are thought to have derivedgymnosperm - plants of the class Gymnospermae having seeds not enclosed in an ovary"

"Progymnosperms were important components of the vegetation from the Middle Devonian through the Lower Mississipian"-lived 380 millions yrs ago. Grows up to 20m tall, with fernlike leaves.*"Like the true gymnosperms, progymnosperms commonly had secondary growth of their vascular tissues (i.e. they produced wood), and some grew to be tall trees"

This is a fossilized stump of Archaeopteris on the OSU campus*"Two major groups of progymnosperms are recognized, the Archaeopteridales and Aneurophytales. A third group, the Protopityales is sometimes recognized, but it is poorly known, and so its relationship to other plants is unclear."*Found in Late Devonian floodplane localities (NY, PA, VA) and forests (North America, South America, Africa, Antartica, Austrailia, Western Europe, China)

*leaves known as archaeopteris *wood is called callixylon

* "Unlike the gymnosperms however, they did not produce seeds, but rather released their spores as do ferns."*"Some progymnosperms were homosporous, producing many identical spores, while others were heterosporous, producing two different kinds of spores. This latter group are thought to be ancestors, or at least close relatives, of the seed plants."

Progymnosperm trunk permineralized in silcia!


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