Premise of research. The Anacardiaceae family is distributed throughout the vegetated continents. The fossil record indicates extensive diversification of the family during the Paleogene and, in particular, during the Eocene. Despite the abundant fossil record of this period, there are only a few reliable anacardiaceous fossils in the Paris Basin. Here, we aim to document newly recognized fossils of Anacardiaceae from the Paris Basin, understand their paleoecology, and discuss their biogeographic history.

Methodology. Thirty-three lignite fruits were examined from two sites, one pre- and one post-the Paleocene-Eocene boundary, i.e., Petit Pâtis (Rivecourt) and Le Quesnoy (Houdancourt). The specimens were photographed and anatomy was studied using computed tomography and histological sections. Comparative analyses were undertaken using available descriptions of fossil and modern fruits of Anacardiaceae.

Pivotal results. A new species is described, Cyrtocarpa biapertura sp. nov., based on a unilocular endocarp with two prominent apertures present on the ventral side, protruding into two lacunae surrounding the locule. Taphonomic analysis indicates that this plant grew close to river banks. Furthermore, a new record of Lannea europaea (Reid and Chandler) Chandler is reported from for the Eocene site.

Conclusions. The occurrence of Cyrtocarpa in both the Paleocene and Eocene floras in the Paris Basin suggests similar vegetation during both time intervals. It is likely that both floras grew under similar subtropical climates. Moreover, it appears that the early Eocene shows an enrichment of the paleodiversity of Anacardiaceae and other plant families in the Paris Basin. The presence of Cyrtocarpa documents a rarely reported disjunction between the Paleogene of Europe and the recent tropical flora of South America.

CT-scan via the AST-RX platform of the Museum national d’Histoire naturelle (Paris, France, MNHN) was used for the Rivecourt specimen Riv-PPB 17 to reconstruct a 3D model, and gain access to the internal organization, the reconstruction was made using the software Mimics Innovation Suite.