Theprogymnosperms are an extinct group of woody, spore-bearing plants that is presumed to have evolved from thetrimerophytes, and eventually gave rise to thespermatophytes, ancestral to bothgymnosperms andangiosperms (flowering plants).[1] They have been treated formally at therank of divisionProgymnospermophyta or classProgymnospermopsida (as opposite). The stratigraphically oldest known examples belong to the MiddleDevonian order theAneurophytales, with forms such asProtopteridium, 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 asAneurophyton 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 thepteridosperm order, theLyginopteridales. In Late Devonian times, another group of progymnosperms gave rise to the first really large trees known asArchaeopteris. The latest surviving group of progymnosperms is theNoeggerathiales, which persisted until the end of thePermian.[4]
^Stewart WN, Rothwell GW (1993).Paleobiology and the evolution of plants. Cambridge University Press. p. 521pp.
^Lang WH (1926). "II.—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".Earth and Environmental Science Transactions of the Royal Society of Edinburgh.54 (2):253–79.doi:10.1017/S0080456800027599.S2CID131163187.
^Serlin BS, Banks HP (1979). "Morphology and anatomy ofAneurophyton, a progymnosperm from the Late Devonian of New York".Palaeontographica Americana.8:343–359.
