Format: ORAL

Simon Beurel 1*, Julien B. Bachelier 2, Alexander R. Schmidt 3, Eva-Maria Sadowski 1

1 Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, Berlin, Germany. 2 Freie Universität Berlin, Institute of Biology/Dahlem Center of Plant Sciences, Berlin, Germany. 3 University of Göttingen, Göttingen, Germany.

Cretaceous fossil flowers are highly significant, if not essential, for understanding origin and evolution of angiosperms. Kachin amber from northern Myanmar represents a valuable source of three-dimensionally preserved mid-Cretaceous (approximately 100-million-year-old) plant fossils, including diverse flowers. Systematic placement of early angiosperm fossils is sometimes challenging as they often possess surprising, unique combinations of floral traits which are absent in Cenozoic taxa. Using the published original microXCT data, we reconstructed the fossil inflorescence from Kachin amber previously assigned to the extant genus Phylica (Rhamnaceae; Shi et al., 2022), visualized new diagnostic features and reassessed the fossil. The dichasial inflorescence bears bisexual flowers with a spiral phyllotaxis, an undifferentiated perianth with a floral cup, stamens with bilocular valvate anthers and a pair of basal filament appendages, inner staminodes, and a semi-inferior ovary. The characteristic flap dehiscence and the pair of basal staminal glands suggest Lauralean affinities. Using the morphological dataset of extant basal angiosperms by Kvacek et al. (2016) we placed the fossil in the Siparunaceae-Gomortegaceae-Atherospermaceae (SGA) clade of the core Laurales. Our results challenge the notion of the presence of a modern genus of Rhamnaceae in the mid-Cretaceous and are in line with most previous age estimates of Laurales and angiosperms as a whole.   References Shi, C., Wang, S., Cai, H. H., Zhang, H. R., Long, X. X. et al. (2022). Fire-prone Rhamnaceae with South African affinities in Cretaceous Myanmar amber. Nature Plants, 8(2), 125-135. Kvacek, J., Doyle, J. A., Endress, P. K., Daviero-Gomez, V., Gomez, B., & Tekleva, M. (2016). Pseudoasterophyllites cretaceus from the Cenomanian (Cretaceous) of the Czech Republic: A possible link between Chloranthaceae and Ceratophyllum. Taxon, 65(6), 1345-1373.