Orvig, T. (1985)
Histologic studies of ostracoderms, placoderms and fossil elasmobranchs. 5. Ptyctodontid tooth plates and their bearing on holocephalan ancestry: the condition of chimaerids. Zoologica Scripta, 14(1), 55–79
DOI: 10.1111/j.1463-6409.1985.tb00178.x
Orvig, T. (1980)
Histologic studies of ostracoderms, placoderms and fossil elasmobranchs 4. Ptyctodontid tooth plates and their bearing on holocephalan ancestry: the condition of Ctenurella and Ptyctodus. Zoologica Scripta, 9(3), 219–239
DOI: 10.1111/j.1463-6409.1980.tb00665.x
Orvig, T. (1967)
Histologic studies of ostracoderms, placoderms and fossil elasmobranchs. 2. On the dermal skeleton of two late Paleozoic elasmobranchs. Arkiv für Zoologie, 19(1), 1–39
Orvig, T. (1951)
Histologic studies of placoderms and fossil elasmobranchs 1: The endoskeleton, with remarks on the hard tissues of lower vertebrates in general. Arkiv für Zoologie, ser. 2, Band 2(2), 321–454