The concept of the polysporangiophytes, more formally called Polysporangiophyta, was first published in 1997 by Kenrick and Crane [REF].
For Banks, rhyniophytes comprised simple leafless plants with terminal sporangia (e.g., Cooksonia, Rhynia) with centrarch xylem; zosterophylls comprised plants with lateral sporangia that split distally (away from their attachment) to release their spores, and had exarch strands of xylem (e.g., Gosslingia).