SUTURAL VARIATION IN AMMONITE ONTONGENY: APPLYING GIS FOR PALEONTOLOGIC ANALYSES

Manship’s (2003) GIS model was developed for analyzing ammonoid suture patterns for classification. Manship (2003) made templates from published sutures of adult specimens of the Late Cretaceous, Coilopoceras springeri (Hyatt), into which unknown sutures were placed for identification, however, no juvenile or early ontogenetic sutures were used. This method is implemented here to visually and quantitatively compare suture patterns and sutural templates of early juvenile through early adult specimens of C. springeri to Manship’s original templates constructed of sutures from adult C. springeri. The GIS software maintains the aspect ratio of the sutural lines, such that comparisons can be made regardless of size.

Through the use of this GIS model, micro-scale ontogenetic variability in the suture patterns of these specimens is apparent. The sutural template of the simpler early ontogenetic specimens does not fit into the adult C. springeri sutural template, due to taller lateral saddles and more inflated elements. However, the early ontogenetic template does fit (almost entirely) into a template constructed from the ancestral Hoplitoides sandovalensis, suggesting a traceable, phylogentic sutural link. As ontogenetic development continues, the major elements become shorter and less inflated, until the template does fit into the adult C. springeri sutural template. Some specimens exhibit the development of a foliole on the umbilical side of the lateral saddle. However, the foliole does not appear in specimens less than 12 millimeters in diameter, and never develops in some individuals, even in adult stages. The lateral saddle of sutures with the foliole is shorter than the lateral saddle of specimens that do not develop the foliole. These results suggest septal elements develop very early and minor elements may vary within individual specimens of Coilopoceras springeri during ontogeny.

Manship, L.L., 2003. Pattern Matching: Implementing GIS applications for paleontological classification of ammonitic sutures. Unpublished Master’s thesis, Bowling Green State University, 149 p.