Psilophytopsida is a now obsolete
class containing one
order,
Psilophytales, which was previously used to classify a number of extinct plants which are now placed elsewhere. The class was established in 1917, under the name
Psilophyta, with only three genera (
Rhynia,
Horneophyton and
Psilophyton) for a group of
fossil plants from the Upper
Silurian and
Devonian periods which lack true
roots and
leaves, but have a
vascular system within a branching cylindrical stem. The living
Psilotaceae, the whisk-ferns, were sometimes added to the class, which was then usually called Psilopsida. This classification is no longer in use.
