THE AMMONOID COILOPOCERAS SPRINGERI ANALYSIS OF INTRASPECIFIC VARIATION USING GIS

Geographic Information Systems (GIS) has been utilized to investigate a pattern matching technique of analyzing shape variation on paleontological material. The shape and complexity of sutures, gross conch morphology, and conch ornamentation are considered to be important characters for Cretaceous ammonoids. These features are widely used in the taxonomy of ammonoids and form the basis for interpretation of phylogenetic histories. Because of the complexity of ammonoids sutures, they are traditionally simply compared visually. The GIS technique allowed for a more objective and precise method for description and comparison of ammonoids suture patterns, as well as conch shape and ornamentation. Analysis of these features using the statistical method of least squares was used to determine the best-fit line, and coefficients of determination (R-square) values were calculated to evaluate the significance of any correlations between sutural measurements and shell morphology. In addition, each of the suture measurements was plotted against the other. The best-fit linear relationship was determined through least squares regression, and coefficients of determination were calculated. There is substantial variation in shell and sutural morphology found among these Coilopoceras springeri specimens. Variation in sutural morphology is gradational and only weakly tied to shell morphology. Variation in sutural morphology appears to have been relatively disjunct from variation in shell morphology.