Fig. 5 in Revision of Middle Ordovician orthoceratacean nautiloids from Baltoscandia

Fig. 5. Histogram of the entire number of observed Orthoceras (n = 66) classified by the expansion rate (e). The frequency peak between e = 0.04 (a = 2.3°) – 0.05 (a = 0.9°) represents O. bifeovatum Noetling and O. regulare Schlotheim, the frequency peak between e = 0.09 (a = 5.1°) – 0.1 (a = 5.7°) represents O. scabridum Angelin.