Fig. 3 in Acanthodian fish trace fossils from the Early Devonian of Spitsbergen

Fig. 3. Idealised trackway of Undichna septemsulcata isp. nov. with the geometric properties (A1, A2, A3 = amplitudes of groove waves; w2 = width of paired grooves; w2', w3a', w3b' = apparent width of paired grooves; λ = wavelength) and the proposed trace maker: an acanthodian with bifurcated and spined pectoral fins, spined pelvic fins and a spined caudal or anal fin.