The first Devonian holocephalian tooth from Poland

A recently found “bradyodont” holocephalian tooth from bituminous shales of the Kowala Quarry, south−western Holy Cross Mountains, Poland, dated as the middle Famennian Palmatolepis trachytera conodont Zone, is described. In spite of its resemblance to the forms often attributed to Helodus, the tooth is referred to as Psephodus cf. magnus (Agassiz, 1838), and supposed to represent the anterior part of the dentition, based on a partly articulated specimen of Psephodus from the Carboniferous of Scotland. The analysis of early helodonts and psephodonts, and other Famennian chondrichthyan crushing teeth, shows numerous similarities in tooth−base structure, such as the reduction of lingual basal extension, loss of articulation devices, development of numerous nutritive foramina, and the tendency to fusion between the teeth in a tooth−family. Based on these shared characters, close phylogenetic relationships between the Protacrodontoidea, Hybodontoidea, and the Holocephali are postulated.