This was a herbaceous plant. The leaflets are (as in all horsetails) arranged in whorls, but the triangular shape of the leaflets is characteristic. They are broadest on top. On this basic pattern many variations occur in the different species. But leaflets on the same plant also can have different shapes. The leaflets on the main axis for example are often laciniate.
In Graissessac we have only come across one species but this one in great numbers.

Sphenophyllum oblongifolium
Sphenophyllum oblongifoliumThe whorls of this species consist of six leaflets in by far most cases, unequal in length, which are arranged in a very characteristic way: like a bow ty. They are always preserved without damage which is an indication that they were attached obliquely to the axis (to catch as much light as possible). The whorls of the thicker stems however are often folded at touching the ground. These leaflets were probably perpendicular to the stem. These leaflets are also differently shaped. They are often long and narrow, nearly needle-like. Some of these narrow leaflets even bear a little hook at the end. The branches of this plant could be very long.
It is thought that this plant was not a real climbing plant, but that it hung over other plants and plants of his own kind (like cleavers and blackberry do).

We have also found spore cones of this species. Click on the photo for more information.