A fossil earthstar (Geasteraceae; Gasteromycetes) from the Late Cenozoic of Puebla, Mexico

The compressed basidiocarp of a fungus belonging to Geasteraceae (Lycoperdales; Gasteromycetes) was recovered from the plant‐bearing Cenozoic strata of the Pié de Vaca Formation, Puebla, Mexico. The fossil specimen consists of an open exoperidium with ten triangular rays, and a central, circular endoperidium with an eccentrical ostiole and irregular surface relief. Scanning electron microscopy revealed a delicate reticulum on the surface of rays and on samples of the endoperidium. An acetolyzed fragment of the endoperidium yielded a few fungal spores, and similar spores were also obtained from an acetolyzed rock fragment adjacent to the fossil specimen. The fossil fungus exhibits the characteristics of extant earthstars; morphological comparison between the extant and the fossil earthstar and the type of spores obtained from the endoperidium of the latter indicate its affinity with Geastrum , although uncertainty in diagnostic characters preclude its assignment to a living species. The report of a complete basidiocarp of Geastrum from the Cenozoic of Puebla may contribute greatly to the knowledge about the spatial distribution and evolutionary history of Geasteraceae and Lycoperdales.