The systematics and ecological role of the orders Equisetales, Filicales, and Marattiales in the Mesozoic fora of Abyek and Jirande, western Alborz

Abstract

Introduction: The Shemshak Group contains a rich and diversified flora in the Abyek and Jirande areas (western Alborz). This paper considers the description of ferns and horsetails from this flora and their ecological significance.
Materials & Methods: First, plant macrofossils of the Shemshak group were collected from a coal-bearing horizon in Jirande area and a coal-bearing horizon in Abyek area. After preparing and taking photos, the samples were studied and the classification of the samples was done based on identification keys.
Results: The study revealed the occurrence of five species of Equisetales, seven species of Filicales, and two species of Marattiales; among these, two genera and five species are recorded for the first time from Iran. Moreover, two species are recorded as new to the western Alborz. Monospecific thickets of Equisetites muensteri, Clathropteris meniscioides, and Dictyophyllum nathorsti were extended across large regions of the lowland, providing an accessible source of food for sauropods. The different parts of these sub-environments were covered by monospecific thickets of Equisetites laevis, Schizoneura paradoxa, Neocalamites hoerensis, N. ishpushtensis, Clathropteris obovata, Dictyophyllum exile, D. nathorsti, and Thaumatopteris brauniana, forming a significant food source for sauropods, while drier habitats within the delta were occupied by Symopteris pseudolobifolia and Marattiopsis barnardii , which had a less important role in sauropod’s diet.
Conclusion: The studied horizon in the Abyek area represents a Rhaetic delta lowland. The studied horizon in the Jirande area is Liassic in age, well developing in parts of delta lowland and delta upland sub-environments.