Diversified fossil plant assemblages from the Maastrichtian in Isona (southeastern Pyrenees)

•A new Maastrichtian locality bearing megafossil plants is reported in the Pyrenees.•The Isona flora is diverse and includes conifers, monocots and a variety of dicots.•The Isona flora shares elements with floras from Europe and North America.•Plant communities in the latest Cretaceous NE Iberia formed mosaics.

At the end of the 1970s, several lower Maastrichtian localities with plant megafossil remains were reported near the village of Isona in the Tremp Syncline of the southeastern Pyrenees. These assemblages include conifers (taxodioids and cheirolepidiaceans), monocot angiosperms (Sabalites palms and likely Pandanaceans) and at least 15 types of magnoliid and eudicot angiosperm leaves. Conifers, Sabalites palms and some eudicots are shared with coeval localities in Portugal, France, Austria and Romania. In addition, Sabalites palms and at least five types of magnoliids and eudicots found here are very similar to fossil leaves reported from Upper Cretaceous localities in North America, suggesting that the Isona flora possibly share some elements with North American floras. Data from the Isona locality also indicate that eudicots dominated the floodplain plant associations in fully continental-influenced terrestrial environments.