Fig. 1
From: Pseudoinversion of septal sutures in Middle Jurassic–Lower Cretaceous non-heteromorph ammonites
Normal and pseudoinverted septal sutures (a, c— after Ward and Westermann 1976). a—Part of suture No. 6 of Glyptoxoceras subcompressum (Forbes), representing pseudoinversion of normal type, with postulated tie-points (solid circles); b—Hypothetical septal suture with pseudoinversion of the transitional type, based on the same specimen; c—Normal septal suture, based on a reverted back to normal. Arrows indicate position of the siphuncle and direction towards aperture. S saddles, L lobes, f folioles, lb lobules; dotted lines are connecting the same tie-points in different examples of sutures