STRATIGRAPHIC DISTRIBUTION OF MORPHOTYPES OF POLYGNATHUS LINGUIFORMIS LINGULIFORMIS HINDE DETERMINED BY MORPHOMETRIC ANALYSIS IN THE MIDDLE DEVONIAN HAMILTON GROUP OF WESTERN NEW YORK

The conodont Polygnathus linguiformis linguiformis Hinde was collected from four horizons in the Middle Devonian Hamilton Group: the Cherry Valley Limestone near the base, Centerfield Limestone in the middle, Windom Shale near the top, and North Evans Limestone at the very top – an interval noted as a time of general evolutionary stasis in shelly organisms for 3.5 million years - to determine if there were detectable changes in the species. Distance and angles between five points on the P₁ element: central node, posterior tip, deflection point on the outer margin, inner anterior end of the platform, outer anterior end of the platform, and the number of ribs on the posterior platform – tongue - were measured, and morphometric analysis was executed using the software programs MorphoJ, tpsUtil, and tpsDig. Results show that stratigraphically there are morphometric changes in the posterior end and platform margins, as well as an increase in the average number of ribs on the tongue. These variations allow recognition of three distinctive morphs of Polygnathus linguiformis linguiformis that seem to have stratigraphic significance. These three morphotypes correspond to the three variants of Polygnathus linguiformis linguiformis identified by Walliser and Bultynck (2011).

Additional co-athors: Putnam, M., Seifert, N., Steen, D., Steinke, R., and Over, D: SUNY-Geneseo.