Taxonomic position of the psilotales in the light of our knowledge of Devonian plant life

Abstract

The order Psilotales, containing the two recent genera Psilatum and Tmesipteris only, is usually classified by taxonomists and palaeobotanists in the phylum Psilophyta. This concept is, in spite of the synangia, based on the primitive general appearance reminding one of that of the Devonian Rhyniaceae. Numerous attempts have been made to derive both genera, including their synangia, from either the Rhvniaceae or from other Psilophyta. These attempts' sometimes led to the acceptance of a series of missing Jinks but this concept is, however, not supported bv palaeobotanical data.

In the opinion of the present reporter the order has kept a primitive general appearance of its Devonian ancestors but in its synangia and in its monolete spores it is more advanced. In its anatomy, its microphyllous leaves, and in its gametophyte perhaps, it shows more affiinity to the phylum Lycopodiophyta. The present reporter classifies the two genera as a separate order in the isosporous Lycopodiophyta. In his opinion the order is to be derived from the Protolepidodendraceae.

Available palaeobotanical data in the Devonian are in support of this concept. The present author has to admit, however, that between the Devonian and recent times no palaeobotanical or palynological data are known to support his concept.