[2] The taxonomic position of Thursophyton has been uncertain; most authors have considered it too imperfectly known to place, or have assigned it to the Lycopodiophyta.

[3] Thursophyton is a genus of terrestrial vascular plants which flourished in the Middle Devonian period.

[2] The stems contain an elliptical exarch xylem having both annular and spirally thickened tracheids; very little is known about the sporangia.

Other species have been suggested (e.g. T. reidii, T. eberfeldense, T. hostimense, T. vahlbergianum) which are usually regarded as synonyms of T. milleri.

Because of the poor preservation of much of this plant material from the Devonian period, it is likely that other synonyms exist e.g. Euthursophyton hamperbachense Mustafa from Germany.