Lycopsids from the Madygen Lagerstätte (Middle to Late Triassic, Kyrgyzstan, Central Asia)

Abstract

Abundant lycopsid remains from the Middle–Late Triassic Madygen Formation in southwestern Kyrgyzstan, Central Asia are described in detail, based on macromorphological and epidermal features. The lycopsid assemblage consists of the subarborescent morphotaxa Mesenteriophyllum kotschnevii, Ferganodendron sauktangensis and Pleuromeiopsis kryshtofovichii, and the herbaceous morphotaxon Lepacyclotes zeilleri that is described by the first time from Central Asia. In addition, two new species are introduced, Isoetites madygensis Moisan et Voigt sp. nov. and Isoetites sixteliae Moisan et Voigt sp. nov., which show a remarkable similarity to extant Isoëtes species, i.e., a short corm and leaves with air channels, suggesting that this lineage goes back to the Early Mesozoic at least. The Madygen lycopsid flora consists of a mixture of subarborescent and herbaceous forms that has not been previously documented from the Ladinian–Carnian onward. The Madygen biota thrived at mid-northern latitudes in an intramontane basin, while most coeval occurrences represent tropical and subtropical biotas. The geographic position and climate are considered to be the main reasons for the unique flora and fauna found in the Madygen Formation, which shows a remarkably high abundance of lycopsids. The Madygen lycopsids show several characteristics indicating (semi-)aquatic habitats.