The value of X-ray approaches in the study of the Messel fruit and seed flora

Abstract

X-ray tomographic methods have been evaluated for their suitability to visualise morphology and anatomy of fossil fruits and seeds preserved in the oil shale of the Middle Eocene Messel Formation (former Lake Messel, near Darmstadt, Germany). Micro-computed tomography (microCT) is suitable for evaluation of gross morphology and tissue preservation. Synchrotron radiation X-ray tomographic microscopy (SRXTM) enables visualisation of gross morphology, tissues, and their detailed cellular structure. Of 30 taxa studied, only 4 exhibit good cellular detail. The reason for lack of detail in other taxa is unclear but may be related to subtle variations in chemical composition or physical structure of their tissues. X-ray tomographic data also permit structures, such as locule casts, to be visualised, giving additional features for comparison with other extinct and extant taxa. X-ray tomography has revealed important features of Messel specimens, which have (1) provided key taxonomic characters and supported recognition of new taxa, some of which are the earliest fossil representatives of modern genera (Pleiogynium, Anacardiaceae; Berchemia, Rhamnaceae), (2) demonstrated the absence of modifications for epizoochory in this flora, and (3) revealed aspects of exceptional preservation relevant to mammal and bird diet (e.g. soft tissue in fruits of Vitaceae).