Late Silurian-Early Devonian tessellated heterostracan Oniscolepis Pander, 1856 from the East Baltic and North Timan

Abstract

Pander (1856, Monographie der fossilen Fische der silurischen Systems der Russisch-Baltischen Gouvernements. Obersilurische Fische. Buchdruckerei Kaiserlichen Akademie des Wissenschaften, St. Petersburg, 91 pp.) first established four Oniscolepis and three Strosipherus species, which later, except O. magna, were referred to Oniscolepis dentata, the name fixed by Rohon (1893, Mémoires de l'Académie Impériale des Sciences de St.-Petersbourg, 41, 1-124) as the senior synonym. Using modern techniques, we redescribe and illustrate morphological and histological varieties of its platelets, tesserae, and scales. No articulated specimen of O. dentata has ever been found. Fragments of head platelets, two branchial plates, an orbital plate (or tessera), and body ridge elements are described for the first time. The microstructure of scales of O. dentata specimens from the East Baltic and North Timan differs only slightly from that of scales from the type locality, Saaremaa Island, Ohesaare Cliff, which has fewer and finer dentine tubules and Sharpey's fibre tubules than the specimens from North Timan. Oniscolepis Pander and Kallostrakon Lankester are united into a new family Oniscolepididae fam. nov. with the type genus Oniscolepis Pander.