The earliest fossil conifer from the Westphalian B of Yorkshire

Abstract

Small charred (fusainized) leaves and leafy shoots, prepared by maceration of an Upper Carboniferous (Westphalian B) shale from Yorkshire are illustrated and described as Swillingtonia denticulata gen. et sp. nov. Examination by s. e. m. has yielded details of stomatal structure and distribution, and some internal anatomy. The uncompressed nature of the epidermal and hypodermal cells, with their open lumina, we attribute to the rigidity of the charcoalified cell walls, that result from exposure to wild fire before fossilization. Most of the leaves are triangular-lanceolate with a denticulate margin and single vascular strand; but a few of the leaves fork, with accompanying dichotomy of the vascular strand. The stomata are sunken and paracytic, and form two bands on the lower (abaxial) face. The leafy shoots show superficial similarity to both conifers and lycopods, but resemble most closely and significantly the conifer Lebachia Florin. Swillingtonia is accordingly assigned to the Lebachiaceae of the Coniferales, and consti­tutes the earliest record of a conifer.