Progymnosperm

The progymnosperms are an extinct group of woody, spore-bearing plants that is presumed to have evolved from the trimerophytes, and eventually gave rise to the gymnosperms.[1] They have been treated formally at the rank of division Progymnospermophyta or class Progymnospermopsida (as opposite). The stratigraphically oldest known examples belong to the Middle Devonian order the Aneurophytales, with forms such as Protopteridium, in which the vegetative organs consisted of relatively loose clusters of axes.[2] Tetraxylopteris is another example of a genus lacking leaves. In more advanced aneurophytaleans such as Aneurophyton these vegetative organs started to look rather more like fronds,[3] and eventually during Late Devonian times the aneurophytaleans are presumed to have given rise to the pteridosperm order, the Lyginopteridales. In Late Devonian times, another group of progymnosperms gave rise to the first really large trees known as Archaeopteris.

Progymnosperm
Temporal range: Middle Devonian–Mississippian
Archaeopteris fossil leaves
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Class: †Progymnospermopsida
Orders

Other characteristics:

Phylogeny

Progymnosperms are a paraphyletic grade of plants.[4][5]

Tracheophyta
 

†Rhyniopsida

 
 
 

Lycopodiophytina (Clubmosses, Spikemosses & Quillworts)

 
 
 

†Eophyllophyton

 
 
 

†Trimerophytopsida

 
 
Moniliformopses

Polypodiophytina (Ferns)

 
Radiatopses
 

†Pertica

 
Lignophytes
 

†Aneurophytopsida

 
Metalignophytes
 

†Archaeopteridopsida

 
 
 

†Protopityales Nemejc 1963

 
 

Spermatophytina (Seed plants)

 
 
 
 
 
 
 
 
 
 
Progymnosperms
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References
  1. Stewart, W.N.; Rothwell, G.W. (1993). Paleobiology and the evolution of plants. Cambridge University Press. p. 521pp.
  2. Lang, W. H. (1925). "Contributions to the study of the Old Red Sandstone flora of Scotland. I. On plant-remains from the fish-beds of Cromarty. II. On a sporangium-bearing branch-system from the Stromness Beds." Transactions of the Royal Society of Edinburgh, 54: 253-279.
  3. Serlin, B. S. & Banks, H. P. (1978). "Morphology and anatomy of Aneurophyton, a progymnosperm from the Late Devonian of New York. Palaeontographica Americana, 8: 343-359.
  4. Crane, P.R.; Herendeen, P. & Friis, E.M. (2004), "Fossils and plant phylogeny", American Journal of Botany, 91: 1683–99, doi:10.3732/ajb.91.10.1683, PMID 21652317
  5. Pelletier (2012). "Empire biota: taxonomy and evolution 2nd ed". Lulu.com: 354. ISBN 1329874005. Cite journal requires |journal= (help)


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