Cheirolepidiacean Foliage From Valangian-Albian Cretaceous Australia

Cheirolepidiacean foliage and pollen from Cretaceous high-latitudes of southeastern Australia

Authors:

Tosolini et al

Abstract:

Cheirolepidiaceae leaves and pollen are recorded from Valanginian–Albian strata of southeastern Australia that were deposited at high-latitudes under cool, moist climates in contrast to the semi-arid or coastal habitats preferred by many northern Gondwanan and Laurasian representatives of this group. Leaves of this family are characterized by thick cuticles and cyclocytic stomata with randomly oriented apertures, arranged in scattered or longitudinal rows or bands. Stomata are deeply sunken and surrounded by four to six subsidiary cells that bear one or two ranks of prominent overarching papillae, which may constrict the mouth of the pit. Three new taxa (Otwayia denticulata Tosolini, Cheirolepidiaceae cuticle sp. A and sp. B) are distinguished based on cuticular features, adding to several previously documented cheirolepid conifers in the Early Cretaceous of eastern Australia. Cheirolepidiaceae foliage is preserved predominantly in fluvial floodbasin settings and is interpreted to be derived from small trees occupying disturbed or low-nutrient sites. The foliage is associated with Classopollis/Corollina pollen and roots characterized by prominent mycorrhizal nodules. A Cenomanian Classopollis type recognised from Bathurst Island, Northern Australia, is recorded for the first time from the Early Cretaceous Eumeralla Formation, Otway Basin. Classopollis locally is rare in Valanginian–Barremian strata of Boola Boola, Gippsland, but constitutes up to 14% of the palynomorph assemblage in Albian strata. This indicates that the family was locally abundant in cool southern high-latitude climates of the Mesozoic, contrary to previous reports of its rarity in this region.