Exploring the interior of cuticles and compressions of fossil plants by FIB-SEM milling and image microscopy.

We present the first study of cuticles and compressions of fossil leaves by Focused Ion Beam Scanning Electron Microscopy (FIB-SEM). Cavities preserved inside fossil leaf compressions corresponding to substomatal chambers have been observed for the first time and several new features were identified in the cross-section cuts. These results open a new way in the investigation of the three-dimensional structures of both micro- and nanostructural features of fossil plants. Moreover, the application of the FIB-SEM technique to both fossils and extant plant remains represent a new source of taxonomical, palaeoenvironmental and palaeoclimatic information. Lay description A microscopic technique consisting of an ion beam and an integrated scanning electron microscope has been used in fossil leaves to cut their outer cover and penetrate their interior. Thus, internal preserved microcavities and related smaller structures inside them have now been observed in three dimensions in fossil plants for the first time. The possibility of detecting and describing these micro/nanostructures may have implications in order to taxonomically classify both extant and fossil plants, at the time it might add additional data to better understand environmental conditions where these ancient plants lived.