Most Latin/Greek names for plants designate a particular group of plants or a single species.
For instance, Viburnum is a genus of many species, Viburnum tinus is a single species.
The confusing thing to note is that Lepidodendron, Leptostrobus, Leptophylloides, and Stigmaria are all used as genera, but unlike most names, each one refers to part of (probably) the same tree. These are what we call 'form genera'.
Lepidodendron and related form genera are explained here