Abstract
The exine ultrastructure of Williamsoniella coronata Thomas from the Bajocian of Yorkshire (United Kingdom) was investigated with light, scanning electron, and transmission electron microscopy. The pollen averages 16.5 μm along its short axis and 24.5 μm along its long axis and is monosulcate, and the nonapertural sculpturing is distinctly verrucate. The pollen wall is homogeneous, and the sulcus membrane is composed of thin exine with scattered small granules. The pollen grains differ in exine sculpturing and pollen wall ultrastructure from pollen grains of the bennettitalean taxa Cycadeoidea dacotensis (MacBride) Ward and Leguminanthus siliquosis (Leuthardt) Kraeusel. They are similar to dispersed pollen grains of Granamonocolpites luisae Herbst from the Triassic Chinle Formation of the United States, supporting the bennettitalean affinity of these dispersed pollen grains. The Bennettitales are palynologically characterized by monosulcate “boat‐shaped” pollen with a homogeneous or granular pollen wall ultrastructure.
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