APPLICATION OF MORPHOMETRIC METHODS TO DISCRIMINATE AMONG MEMBERS OF THE IDIOGNATHODUS SIMULATOR SPECIES GROUP AND IMPLICATIONS FOR QUANTITATIVE DISCRIMINATION OF P1 ELEMENTS OF OZARKODINIDA CONODONTS

A morphometric procedure was established to discriminate among morphotypes of P₁ elements of the conodont Idiognathodus simulator (Ellison) from the Upper Pennsylvanian Heebner Shale of Midcontinent North America. Oriented line segments are created by connecting a series of landmarks, each with an X and Y coordinate value, on a digital image of the P₁ element. The landmarks are the central node, dorsal tip, caudal, ventral and rostral extent of transverse ribs on either side of the eccentric groove, and the dorsal and ventral extensions of the adcarinal ridges and lobes. Subjecting the coordinate data to the appropriate eigen analysis can describe either the linear variation between pre-classified groups (i.e. quantify discrimination), or aid in determining the linear variation within one group (i.e. aid in exploratory discrimination). Principle component analysis of features can locate and describe the linear variation between all the members of a sample. Canonical variant analysis of these data can be used to locate and describe the linear differences between pre-designated groups. Simulated random resampling of the data permits the building of morphospace models. These models allow for quantified discrimination of morphologies and can be updated as necessary with the addition of new data. Modification of the I. simulator morphometric protocol should facilitate the quantitative discrimination of other morphologically similar conodont P₁ elements, especially those of the order Ozarkodinida.