“…For each psammosteid taxon, text and graphic data on the type specimens were used (Elliott, Mark-Kurik, and Daeschler, 2004;Elliott and Mark-Kurik, 2005;Halstead Tarlo, 1964aLyarskaya, 1971;Mark-Kurik, 1968, 1999Novitskaya, 1965Novitskaya, , 2004Obruchev, 1940;Obruchev and Mark-Kurik, 1965;Růžička, 1929;Tarlo, 1961). The most recent data on the general morphology, ornamentation and histology of psammosteids were also encoded (Glinskiy, 2014;Glinskiy and Mark-Kurik, 2016;Glinskiy and Nilov, 2017;Glinskiy and Pinakhina, 2018;Keating, Marquart, and Donoghue, 2015;Moloshnikov, 2001). All characters are discrete (binary or multistate), mostly unordered, but 21 multistate characters are ordered as specified by the relationship of character states within the transformation series (1,8,16,21,30,31,38,54,57,64,71,79,81,83,86,87,88,89,99,108,117).…”