How can girdling leaf traces help scientists identify cycad fossils?

Girdling leaf traces are a key diagnostic feature used by scientists to distinguish between cycad and cycadeoid fossils. In cycad stems, the vascular strands follow a circuitous route to the leaf bases, a pattern that is clearly visible when examining cross sections of the stems. This specific arrangement of internal vascular connectives is a characteristic unique to cycads and does not occur in cycadeoids, seed ferns, or coniferophytes.1