Progymnosperm

Progymnosperm Temporal range: Middle Devonian–Mississippian PreЄ Є O S D C P T J K Pg N
Archaeopteris fossil leaves
Scientific classification
Kingdom:	Plantae
Division:	Tracheophytes
Class:	†Progymnospermopsida
Orders
†Aneurophytales †Protopityales †Archaeopteridales

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. 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.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, 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.

Other characteristics:

Progymnosperms are a paraphyletic grade of plants.

†Rhyniopsida

Lycopodiophytina (Clubmosses, Spikemosses & Quillworts)

†Eophyllophyton

†Trimerophytopsida

Polypodiophytina (Ferns)

 †Pertica 

 †Aneurophytopsida 

 †Archaeopteridopsida 

 †Protopityales Nemejc 1963 

 Spermatophytina (Seed plants)

An updated classification of Progynopserms based on the work by Novíkov & Barabaš-Krasni 2015 with plant taxon authors from Anderson, Anderson & Cleal 2007

...
Wikipedia