Trilobated Lauraceous leaves from the Upper Cretaceous Olmos Formation, Coahuila, Northern Mexico

The Olmos Formation in Coahuila, Mexico has crucial information about the Cretaceous floras in northern Mexico. Its plant diversity is high and represents one of the most studied paleofloras for this region; angiosperm leaves are the main plant organs that can be found and serve as the primary source to reconstruct this paleoflora. Since a large part of the foliar diversity of this Formation has yet to be described, its documentation is essential to discuss further the history of plant establishment in southern North America. Through a detailed description and statistical comparison of its foliar architecture with other fossil and extant leaves, the new trilobate leaf is assigned to the fossil genus Pabiania Upchurch and Dilcher, a group found so far exclusively in the Cretaceous of the United States and now, for the first time in Mexico. Its leaf architecture suggests it is closely related to the Order Laurales and probably an extinct group within Lauraceae.