An unusual megaspore of uncertain systematic affinity from Lower Cretaceous deposits in south-east England and its biostratigraphic and palaeoenvironmental significance

Abstract

An unusual megaspore has been recorded from beds within the Weald Clay Group of south-east England. Described as Clockhousea capelensis gen. et sp. nov., it is characterised by having a thick outer layer of exine consisting of closely packed columnar to clavate elements with constricted bases attached to a perforated inner layer and a sculpture that ranges from having the appearance of a negative reticulum through closely spaced verrucae to a mixture of verrucate and essentially baculate elements, all of which are surface manifestations and extensions of the underlying structure. These characters do not readily indicate a systematic relationship with any known heterosporous plant genus or family. The localised occurrence and relative abundance of the spores in a few beds suggest that some of the parent plants grew close to water bodies where they were deposited and preserved. Their recovery from sediments of late Hauterivian–early Barremian age indicates that the species has potential as a biostratigraphic marker in the upper Wealden succession of southern England and perhaps elsewhere.

Keywords:

• Cretaceous
• Hauterivian
• Barremian
• Weald Clay
• UK
• mesofossil
• megaspore
• Clockhousea

Acknowledgements

I thank Mrs Lorraine Morrison (Aberystwyth University) for sample processing, Dr Peter Morris (MicroStrat Services, Devon) for photographing the specimens depicted in Figure 1, and Mr Richard Hartley (Manchester University) for help in preparing the figures. I am grateful for the thoughtful comments on the manuscript provided by two anonymous referees.