Fruits and flower of Icacinaceae Miers from the Early Eocene of the Le Quesnoy locality (Oise, France)
Résumé
The study of the paleoflora of Le Quesnoy (early Eocene, Paris Bassin) has been mainly focused on ambers and pollen embedded in amber and lignitic fossil endocarps of the Menispermaceae family (De Franceschi and De Ploëg, 2003; Jacques and De Franceschi, 2005). However, the diversity of this flora remains understudied. In particular, fossils of the Icacinaceae family are the most representative of this site with 185 nearly complete lignitic endocarps and numerous fragments. Here, we described three species within which two are new. These species show affinities with taxa described in other Eocene localities of Europe (London Clay, Reid and Chandler, 1933) and North America (Clarno Formation, Manchester, 1994) and in the close Paleocene locality of Rivecourt. In addition, we described a new flower preserved in amber. The flower from Le Quesnoy has Asian affinities with the extant genera Natsiatum Buch.-Ham. ex Arn. and Hosiea Hemsl. & E.H. Wilson and represents an extinct new genus of Icacinaceae. The endocarps species presents the diagnostic characters of the modern African genus Iodes Blume. The extant Icacinaceae are usually lianas. These forms are frequent in megathermal forests, which could have occurred in Europe during the early Eocene global warming. They indicate mixed vegetation with Asiatic and African affinities corresponding to a successional flora during the PETM. In particular, the « Ibeam » ridge shape observed in one of these fossil taxa could correspond to an innovation linked to a new ecological niche and associated with the emergence of new mammal frugivorous groups during the global warming. Further study of this remarquable site, with a focus on the other present families, is therefore necessary in order to describe more precisely the paleogeographical links of Le Quesnoy flora with past and extant ones and to highlight the association between flora and fauna through time.