This study presents a detailed analysis of an exceptionally well-preserved articulated specimen of the trilobite Trimerocephalus from the Late Devonian of the Holy Cross Mountains in Poland. X-ray microtomography reveals the oldest direct evidence for a moulting episode known from the fossil record. The process of moulting as well as associated features observed in the investigated specimen are interpreted by comparison with extinct and extant Xiphosurida arthropods, which survived global P/T extinction and are among the closest extant relatives of trilobites. A very special moment frozen in time and space millions years ago provides rare insights into the behavior and physiology of these long-extinct arthropods.

The ability to see and understand the three−dimensional structure of an investigated object plays a key role in studying fossil remains.

Several brachiopods which belong to the same genus Horridonia of late Early and early Late Permian age in Spitsbergen and Poland, respectively, have been petrographically and geochemically analysed to verify seasonal variation in stable carbon and oxygen isotope values for palaeoclimatological implications. The specimens of Horridonia timanica from Spitsbergen show distinct cyclicity reflective of seasonal pattern, while those of Horridonia horrida from Poland do not. These differences are explained by the fact that the former lived at high palaeolatitudes at the northern margin of the supercontinent Pangaea where the seawater temperature differences between winter and summer seasons were greater, as expressed in the isotopic composition of the skeletal materials. In contrast, the shell growth of Horridonia horrida was subjected to strong evaporative influence by climatic variations in the eastern area of Pangaea.

13 C values ob− tained for durophagous teeth of the hybodont selachian, Lissodus, probably reflects its mi− gratory behaviour and perhaps a greater feeding diversity. X−ray microcomputed tomogra− phy (XMT), a non−destructive technique, is used for the first time in order to elucidate de− tails of tooth histology, the results of which suggest that the method has considerable poten− tial as a future analytical tool.

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