Early Devonian miospore assemblages from ‘La Gileppe’ (Eastern Belgium) include five varieties of trilete spore belonging to the genus Emphanisporites. These five varieties show a continuous variation of their morphological characteristics. The variation in morphological characteristics can be related to the evolution of morphological features and allows us to define the Emphanisporites micrornatus Morphon. A statistical evaluation of this population highlights the interdependence of almost all morphological parameters. This study proves the increase in size of ornamental and structural parameters over several million years. The biometric changes and the progressive replacement of older morphotypes by younger ones indicate that a temporal link exists between these different varieties. Two phylogenetic hypotheses for the E. micrornatus Morphon are proposed. This morphological evolution is so far observed only on the Eastern Old Red Sandstone Continent and defines a palaeophytogeographic sinuosus–zavallatus Province.