NEW EPHEDROID PLANT FROM THE LOWER CRETACEOUS KOONWARRA FOSSIL BED, VICTORIA, AUSTRALIA

A revision of the Lower Cretaceous Koonwarra material first assigned t o angiosperms and subsequently to sphenopsids shows morphological and anatomical characters typical of ephedroid (gnetophyte) affinities. Sh oots are preserved as clayey-ferruginous films deposited beneath the c uticle reflecting with the interior relief of the epidermal cell patte rn or subepidermal sclerenchymous strands (rugulate striations) and va scular tissue of the intermodes. The articulate shoots are similar to Ephedra foliata and some other extant species with 3-4 decussate, basa lly connate leaves at each node, sunken stomata in intercostal zones, alternating large and small vascular bundles, paired leaf traces, and the morphology of tracheary elements, but differ in the leaf number pe r node ranging from two to eight and in the considerably lower ratio l eaves to internode vascular bundles. A new genus and species Leongathi a elegans is described. The co-occurrence of gnetophytes and early ang iosperms in the lower Aptian of Koonwarra is of certain evolutionary a nd palaeoecological significance. The Koonwarra material increases the known diversity of the Cretaceous gnetaleans by presenting a hitherto unrecorded Ephedra-like shoot morphology.