Morphological variation of stratigraphically important species in the genus Pilosisporites Delcourt & Sprumont, 1955 in the Gippsland Basin, southeastern Australia

Abstract

Seegets-Villiers, D.E. and Wagstaff, B.E. 2016. Morphological variation of stratigraphically important species in the genus Pilosisporites Delcourt & Sprumont, 1955 in the Gippsland Basin, southeastern Australia. Memoirs of Museum Victoria 74: 81–91. Three hundred and ninety eight mudstone samples of Early Cretaceous age from the onshore part of the Gippsland Basin in southeastern Australia were used to ascertain the morphological variation in three species of spores in the genus Pilosisporites. In Australia all species of Pilosisporites are biostratigraphically useful and this study confirms that in the Gippsland Basin the ranges of Pilosisporites notensis, Pilosisporites parvispinosus and Pilosisporites grandis are as defined by some previous authors. Morphological variations of these three taxa from the published descriptions are discussed. In the case of P. grandis and P. parvispinosus the main variation was in the size of specimens, however P. notensis showed sculpture variations in regard to element size, type and distribution. Two distinct types of this species were defined with only one occurring in the youngest part of the section. Modern fern species can exhibit similar spore sculpture and size variations as a result of polyploidy. This could possibly be the cause of the variations in all three species of Pilosisporites and also their short-lived, in geological terms, species ranges.