The Molí del Baró-1 site, a diverse fossil assemblage from the uppermost Maastrichtian of the southern Pyrenees (north-eastern Iberia)

• Molí del Baró-1 is a diverse fossil assemblage from the upper Maastrichtian Iberia.
• It includes plants, invertebrates and vertebrates.
• Its crocodile record is among the most diverse in the Maastrichtian of Europe.
• Deposition mostly occurred in a pool formed at the edge of a river meander.
• Crocodiles, theropods and hadrosauroids were the main faunal elements of this biota.

The Molí del Baró-1 site (north-eastern Iberia) has yielded one of the richest fossil assemblages of the continental upper Maastrichtian from western Europe. It includes abundant plant (charophytes, sporomorphs, angiosperm leaves, seeds and logs), invertebrate (mollusc shells, partial insect exoskeletons and eggs) and vertebrate (teeth, bones, eggshells) fossils. The fossil assemblage is composed of both parautochthonous and allochthonous remains that mostly deposited in a pool formed at the edge of a meandering river. Plant megafossil evidence suggest that at least three angiosperm species (a willow-like dicot, palms and a likely typhacean monocot) formed the plant community growing in this fluvial environment. Tooth remains indicate that crocodylomorphs were diverse (including atoposaurids, ziphosuchians and eusuchians) which together with small theropod dinosaurs likely consumed prey carcasses or scavenged near the depositional setting. Prismatoolithid eggshells also suggest the presence of nearby nesting area of theropods. On the other hand, hadrosauroids apparently dominated phytophagous faunas including lambeosaurines as well as more basal forms. The taxonomic composition of the Molí del Baró-1 site matches the expected for the timespan and environment and represents a relevant locality to know the diversity of the latest Cretaceous terrestrial ecosystems in south western Europe.