Hamatophyton verticillatum

Hamatophyton verticillatum is a species of the extinct Sphenophyllales horsetails.

Description
Axes of this plant are pseudomonopodial with axial trichomes or spines and nodal whorls of sterile leaves. Leaves are dimorphic and sometimes contain trichomes or spines. When mature, primary xylem is exarch and the secondary xylem lacks parenchyma.