Paratropical rainforest from the Olmos Formation (upper Campanian), Coahuila, Mexico

We present new data based on physiognomic analysis of the Olmos Formation leaf flora, indicating it represents a paratropical rainforest with an inferred mean annual temperature (MAT) of 20-24 degrees C and mean annual precipitation (MAP) of 1210.8-2878 mm, with a growing season precipitation of 1089-1306 mm. Additionally, we found some leaves that we grouped according to their morphological characteristics resembling Laurales, Lauraceae, Violaceae, Rhamnaceae, and other eudicot groups recorded in Cretaceous assemblages from North America. This evidence suggests the climate for the Olmos Formation is significantly wetter than those reported for other Campanian continental assemblages from the Western Interior, where this geological formation belongs. Instead, the inferred climate of the Olmos Formation is strikingly similar to those reported from early Paleogene assemblages from the Western Interior. Our analysis of the Olmos Formation leaf flora suggests that angiosperm-dominated paratropical forests in North America predate previous estimates that placed it during the Paleogene. (c) 2023 Elsevier Ltd. All rights reserved.