The Cheirolepidiaceae, an extinct family of coniferous plants that thrived during the Mesozoic Era, are well known through their distinctive Classopollis pollen. Although long thought to have declined globally during the Late Cretaceous, isolated occurrences of Classopollis in Paleocene deposits have sparked debate regarding the survival or reworking of this lineage beyond the Cretaceous–Paleogene (K/Pg) boundary. In this study, we document the occurrence of exceptionally well-preserved Classopollis pollen within Paleocene inter-volcanic sedimentary rocks of the Antrim Lava Group in Northern Ireland. Detailed morphological analyses using transmitted light microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) reveal Classopollis pollen with uniformly thick tectate exines, well-developed baculate infratectal layers, and a dense nano-spinulose supratectal ornamentation. These features can be compared with Barremian-aged English specimens and support a Cretaceous origin. Palynological assemblages also include other reworked Cretaceous taxa and clastic components derived from the underlying Ulster White Limestone Formation, a Santonian–Early Maastrichtian unit exposed within the catchment. The stratigraphic context and preservation state of the Classopollis grains suggest that they were reworked rather than representing in situ Paleocene vegetation. This study supports the interpretation that post-K/Pg occurrences of Classopollis in the Antrim Basin are best explained by sedimentary recycling of Late Cretaceous deposits, adding to the broader discussion on Cheirolepidiaceae persistence and paleoecological relict status in the Paleogene.
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