Ferns are widespread in the Carboniferous and Permian. Many had a tree-like growth habit like modern tropical tree ferns. However, though superficially looking very similar, the modern tree ferns are not directly related to the the Palaeozoic ones. Sometimes it is very difficult to distinguish true fern foliage from seed fern foliage; especially when fructifications are still unknown. In such cases fern(-like) foliage is accommotated in the informal category pteridophylls.
Psaronius melanedrus - Palaeobotany, Münster