This can cause some confusion: firstly, a fossil was probably surrounded with 4-5 times its width in (unpreserved) vascular tissue, so the organisms were much wider than the internal casts preserved.

[citation needed] Further, the fossil gets narrower as it attaches to a rhizoid, a place where one would expect there to be the highest concentration of vascular tissue (as this is where the peak transport occurs).

Further organ genera belonging to sphenophytes include: The trunks of Calamites had a distinctive segmented, bamboo-like appearance and vertical ribbing.

This type of asexual reproduction would allow them to spread quickly into new territory, and help to anchor them firmly in the unstable ground along rivers and in newly deposited delta sediments.

The rhizomes of Calamites look quite similar to the stems in most cases, but have nodes that get progressively closer together as they approach the apical area (the growth tip that spreads outward through the soil).

The genus Calamites is placed in the family Calamitaceae in the plant class Equisetopsida (formerly known as Sphenophyta) in the fern allies division Pteridophyta.