The rise and demise of Podozamites in east Asia—An extinct conifer life style

Abstract

In the Late Triassic–Early Jurassic, forests dominated by Podozamites—an apparently deciduous, shoot-dropping conifer with broad, multi-veined leaves—were extensive in what were the mid-latitudes of eastern Asia. Podozamites was the only conifer in many forests of this region, and at times appeared to have formed an almost mono-specific vegetation. Podozamites appears to have been little-effected through the Triassic–Jurassic transition, but responded to climate changes later in the Jurassic. The Chinese region progressively dried through the Middle Jurassic and aridity had developed in some areas by the Late Jurassic–Early Cretaceous. The centre of distribution of Podozamites shifted north, to the Siberian region, where conditions remained wet. There, it typically coexisted with conifers having a diverse range of smaller leaf morphologies.By the late Albian angiosperms had arrived in the Siberian area and risen to dominance. Some time after this event, Podozamites became extinct. This is significant, as it represents the permanent extinction of a unique lifestyle—a deciduous, broad-leaved and multi-veined conifer.The broad history of Podozamites raises some interesting issues:1.The existence of a large, dominantly deciduous vegetation at mid-latitudes in the Late Triassic–Early Jurassic is little discussed.2.It is unexpected that as broad-leaved angiosperms took over, amongst the conifers it was the broad leaved, multi-veined Podozamites that became extinct. This is the morphology that might have been expected to compete with the apparently more shade-forming angiosperms. Instead, it was the smaller leaved and single-veined conifers that remained to coexist with the angiosperms.