Fig. 26 in The cephalopods of the Boda Limestone, Late Ordovician, of Dalarna, Sweden

Fig. 26. Variability of the angle of expansion in fragments of different diameters of Isorthoceras wahlenbergi Niko, 2008 (black points) and Isorthoceras dalecarlense Kröger et al., 2010 (grey points). The black circles refer to specimens figured in Kröger et al. (2011: fig. 11) and identified as I. dalecarlense, therein. The complete dataset, presented herein, demonstrates that a definite species distinction by angle of expansion and size alone is impossible in fragmentary specimens with angles of expansion between 6° and 8°. Additionally, the complete dataset reveals that specimens with conch diameter> 7 mm and angle of expansion> 8° in Kröger et al. (2011: fig. 11) must correctly be interpreted as fragments of I. wahlenbergi.