Our results are consistent with Neuburg's hypothesis, showing progressive increase in the frequency and diversity of leaf cell dimorphism in protosphagnacean mosses from the early to the late Permian and indicating that a leaf developmental pathway very similar to that of extant Sphagnum appeared in the late Permian, bolstering the hypothesis that extant Sphagnum originated from Permian protosphagnaceans.
Ignatov et al. (Wed,) studied this question.