ABSTRACT
Suture patterns in shelled cephalopods are periodic structures and can be described using Fourier methods when points along the pattern are described by two parametric equations. One equation describes the angular position along the circumference of the phragmacone, and another describes the height along the length of the shell. The angular position is amenable to Fourier description transformed to the difference between the observed angle and the angle expected if the suture line were straight. An accurate reconstruction of ammonitic suture patterns is accomplished with few amplitudes. Applying the method to the digitized suture patterns provides a more accurate means of interpolation than linear interpolation, necessary for comparison between suture patterns. Simple "nautilitic" and complex "ammonitic" suture patterns from the literature are used to demonstrate application of the method. Ontogenetic series of suture patterns may develop first by increasing variability in their height, and only later by increasing variability in the angular positions. The method invites new approaches of analysis, including different approaches to nearest neighbor analysis to determine patterns of similarity between suture patterns.
Raymond F. Gildner. Paleontological Research Institution, Ithaca, NY 14853
Correspondence address: Department of Geosciences, Indiana University, Purdue University, Fort Wayne, Fort Wayne, IN 46805
KEY WORDS: cephalopods, ammonites, septa, suture patterns, Fourier analysis, modeling
Copyright: Paleontological
Society - September 2003
Submission: 29 April 2002 - Acceptance: 6 August 2003
