Revision of the Late Devonian ptyctodonts (Vertebrata, Placodermi) from southern Poland

New studies on Frasnian ptyctodonts, including the revision of historic material in addition to the description of new material, have resulted in the detailed description of two species of Ptyctodus (Ptyctodus obliquus, Ptyctodus kielcensis), eight indeterminate specimens of Ptyctodus sp. from the Holy Cross Mountains and two specimens from Debnik near Krakow, four indeterminate specimens of Rhynchodus sp., and two specimens of Ptyctodontidae gen. et sp. indet. from the Holy Cross Mountains. One of the described species (P. kielcensis) appears to be endemic for the Holy Cross Mountains region. Based on general knowledge of the Frasnian stratigraphy of the Holy Cross Mountains and on the conodont material obtained from the fragments of the sediments attached to specimens, it was possible to define the predetermined subdivision of the Frasnian as ranges of conodonts and the fauna to be placed within conodont zones. Previously only antiarchs, bottom-feeding placoderms, had been recovered from the Lower and Upper Kellwasser horizons from this area (Plucki); thus, the occurrence of ptyctodonts represents an additional placoderm taxon. This work describes the first placoderm remains from Debnik near Krakow, which also represent the first described placoderms from an area other than the Holy Cross Mountains.