New ephedroid plant from the Lower Cretaceous Koonwarra Fossil Bed, Victoria, Australia

Abstract

A revision of the Lower Cretaceous Koonwarra material first assigned to angiosperms and subsequently to sphenopsids shows morphological and anatomical characters typical of ephedroid (gnetophyte) affinities. Shoots are preserved as clayey-ferruginous films deposited beneath the cuticle reflecting either the interior relief of the epidermal cell pattern or subepidermal sclerenchymous strands (rugulate striations) and vascular tissue of the internodes. The articulate shoots are similar to Ephedra foliata and some other extant species with 3–4 decussate, basally 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 per node ranging from two to eight and in the considerably lower ratio of leaves to internode vascular bundles. A new genus and species Leongathia elegans is described. The co-occurrence of gnetophytes and early angiosperms in the lower Aptian of Koo...