A reappraisal ofPhyllopteroidesMedwell (Osmundaceae) and its stratigraphic significance in the Lower Cretaceous of eastern Australia

Abstract

Four species of Phyllopteroides are present in the Lower Cretaceous of eastern Australia: P. laevis sp. nov., P. serrata sp. nov., P. dentata Medwell 1954a and P. lanceolata (Walkom) Medwell 1954b. The first three of these species occur in successive stratigraphic horizons in the Victorian Lower Cretaceous; they form a probable evolutionary lineage showing progressive changes in leaf morphology, particularly shape and dentation. Well-preserved osmundaceous fructifications (Cacumen expansa gen. et sp. nov.) occur closely associated with P. dentata leaves, strongly suggesting that Phyllopteroides is an osmundaceous fern. The Lower Cretaceous megafloral zonation of Douglas (1969) is revised by defining the zone boundaries as the first occurrence of the nominate Phyllopteroides species for each zone. This modified zonation can be correlated with the Lower Cretaceous microfloral zonation, and is applicable to Lower Cretaceous floras throughout eastern Australia.