Placodermi of the Prague Basin (Lower Palaeozoic of the Barrandian area)

Placoderms are restricted to the Devonian in the Prague Basin, occuring on localities dated from the Lochkovian to the Givetian. Černá rokle near Kosoř with the Radotin Limestone is the richest placoderm bearing locality. A revision of specimens from collections of the National Museum in Pra- gue confirms occurences of three species of two genera belonging to the pla- coderm order Acanthothoraci: Radotina kosorensis Gross, 1950; Radotina tesselata Gross, 1958 and Kosoraspis peckai Gross, 1959. Genus Holopeta- lichthys was accepted as valid and a diagnosis of H. primus (Barrande, 1872) was amended. Its assignment to higher taxonomic units remains uncertain. Four morphological types of undeterminable specimens classified in the order Arthrodira are defined. Some previously unpublished morphological structures are figured and described: the median dorsal plate of the thoracic armour of R. kosorensis and its relation to the head shield, the cranial cavities and trunk shield plates of R. tesselata, a well preserved neurocranium and scales of K. peckai, the trunk shield and vertebral column of H. primus and large dermal plates of each Arthrodiran morphotype. The placoderm diversity in the Prague Basin was lower compared to ne- ighbouring areas at the beginning of the Devonian (Lochkovian and Pra- gian). Only..