Vascular Cryptogam Plants of the Khoshyeilagh Formation, Northern Shahrud, Eastern Alborz Ranges

Fragmentary, indifferently preserved, and of low diversity plant remains occur in basal part of the Khoshyeilagh Formation, northern Shahrud, eastern Alborz Ranges. The oldest hitherto reported from Iran, the remains are essentially assignable to lycophytes and psilophytes. Additionally, spores retrieved from the Khoshyeilagh Formation with reference to available data on spore-plant relation-ships denote that Phaeophyta, Rhyniopsida (Rhyniales and Trimerophytales), Zosterophyllopsida, Barinophytopsida (Barinophytales), Filicopsida (Cladoxylales and Zygopteridales), Lycopsida (Drepanophycales), Equisetopsida, and Progymnospermopsida (Aneurophytales and Archaeopteridales) were perhaps the main sources of sporae dispersae. Variations in the samples examined of approximate ratio of land-derived to marine palynomorphs, however, evidently support stabilization of marginal marine environments and noticeable modification in complexion of the contemporaneous coastal vegetation upward in the section investigated. Vertical distribution of the plant remains, associated palynofloras, and available faunal indications collectively permit the host strata to be dated as early Middle Devonian (Eifelian). Poor preservation of the plant remains perhaps conveys accumulation during flooding. A river with alternating floods emasculating its bank overtaken by Protolepidodendron and Dawsonites may be envisaged.