Extroparvum occidentale gen. et sp. nov. and the Cretaceous diversification of Lauraceae

The fossil record of Lauraceae extends back to the Early Cretaceous and comprises numerous flowers. However, phylogenetic relationships of many of these fossil flowers remain unresolved. To better understand the early evolutionary history of Lauraceae, we conducted phylogenetic analyses of living and extinct members of the family and described a new fossil flower from the Coniacian of British Columbia, Canada.

Serial sections of the new fossil flower were prepared and used to create a three-dimensional reconstruction. We performed a series of phylogenetic analyses, including total-evidence analyses using a novel morphological matrix, to analyze the new fossil flower and 16 previously described fossil flowers. Phylogenetic uncertainty was explored for each taxon, and phylogenetic pseudofossilization analyses were conducted to test whether our floral data set can accurately recover systematic relationships within Lauraceae.

The Eden Main fossil flowers are assignable to Lauraceae and represent a new genus and species: Extroparvum occidentale. Phylogenetic analyses recovered E. occidentale and 12 fossil flowers among Lauraceae. Phylogenetic uncertainty within Lauraceae was high for many of the fossils, but we identified two taxa as crown-group members that can be employed as new node calibrations for the family. Pseudofossilization analyses indicated that our floral data set can accurately recover taxa within crown-group Lauraceae with high support.

Our work adds to the known Cretaceous diversity of Lauraceae and provides the first phylogenetic evidence of crown-group Lauraceae diversifying by the Late Cretaceous. Furthermore, our novel morphological data set lays an important foundation for directly integrating fossil flowers into macroevolutionary studies of the family.