Deformed pollen have been found in all the previous extinctions (late Devonian, late Permian and Triassic-Jurassic). There were no pollen in Ordovician-Silurian.

These deformations happened for a depletion in the Ozone layer, and then an high UV radiation, caused by intense volcanism. However, if volcanism caused also late cretaceous mass extinction, why i can't find any deformed pollen reference in the literature? The problem is never been raised before. In late Cretaceous an high % of plant's species died, like in other mass extinctions, but i couldn't find any reference of deformation/aberrations in pollen. The extinct species just disappeared.

Let me know if you have ever found these cases in the literature, maybe they are hidden in some intuitive title article