Fruits of Anacardiaceae from the Paleogene of the Paris Basin, France

Abstract

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 before and one after 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, Cyrtocarpa biapertura sp. nov., is described on the basis of a unilocular fruit with two prominent apertures present on the ventral side of the endocarp, protruding into two lacunae surrounding the locule. Taphonomic analysis indicates that this plant grew close to riverbanks. Furthermore, a new record of “Lannea” europaea (Reid and Chandler) Chandler is reported for the Eocene site. Conclusions. The occurrence of Cyrtocarpa in both the Paleocene and the 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.