PERMINERALIZED PLEUROMEID LYCOPSID REMAINS FROM THE EARLY TRIASSIC ARCADIA FORMATION, QUEENSLAND, AUSTRALIA

Dispersed permineralized cones, stems, rhizomorphs and roots attest to a diversity of pleuromeids in the Early Triassic Bowen Basin of easte rn Australia. The lack of organic connection precludes whole plant ide ntification and the material is assigned to form-taxa. Cones are refer red to Cylostrobus clavatus Cantrill et Webb, sp. nov., a bisporangiat e cone, and Pleuromeia reniformis Cantrill et Webb, sp. nov., a monosp orangiate cone. The stem Pleurocaulis rewanense Cantrill et Webb, gen. et sp. nov, has a central exarch protostele surrounded by an aerenchy mous inner cortex. Two unlobed rhizomorphs with internal anatomy are r ecognized, Helicorhiza duckworthensis Cantrill et Webb, gen. et sp. no v, and Cidarophyton rewanense. Duckworthia isoeteformis Cantrill et We bb, gen. et sp. nov. is a form taxon for roots that are monarch with a n eccentric vascular bundle and were presumably borne by the rhizomorp hs. The anatomy of the plants in conjunction with the sedimentary sett ing and high palaeolatitudes suggests that the Bowen Basin lycopsids w ere small ephemeral plants that exploited seasonally wet conditions. ( C) 1998 Elsevier Science B.V. All rights reserved.