FUNCTIONAL INTERPRETATION USING PA-ELEMENT MORPHOLOGY AND MICROWEAR PATTERNS IN DESMOINESIAN (PENNSYLVANIAN) IDIOGNATHODID CONODONTS

Purnell showed that microwear patterns on paired conodont Pa-elements from natural assemblages could be used to determine element function. The same conclusions can be drawn from disarticulated elements using wear patterns and element morphology. Application of this technique can be used to resolve issues of function in specimens without known natural assemblages.

Original blade texture is fibrous on the oral half of the blade in the specimens observed. The oral surface of the platform has a polygonal texture. The aboral surfaces of the element are smooth and featureless. Wear on conodont elements is expressed in two ways. Wear related to friction results in smoothing to the complete removal of original texture. Wear related to force (movement and occlusion) results in blunting of sharp features, truncation of textures, and lateral smearing of surface ornamentation.

The blade serves a slicing function as indicated by the tight occlusion of the dorsal blade on both dextral and sinistral elements. The caudal side of dextral blades and rostral side of sinistral blades are highly polished. No original texture is visible, and the shape of the dorsal denticles is flattened on the polished side. This indicates direct contact between the opposing elements. Denticle tips are blunted and worn on the dorsal facing surfaces, indicating the trapping and slicing of food as blade occlusion occurs. The platform serves a crushing and bruising function as indicated by the presence of numerous transverse ridges that are steepened on the ventral facing side. As the platforms of two elements close together, food is flattened on the steep ventral side of the ridge. Direct element contact is indicated by the truncation of the platform texture at the ridge crest on the dorsal facing side. Both the blade and the platform of Pa-elements function to transport food to the central platform of the element. Denticles on the blade are oriented toward the center of the platform. Transverse ridges on the platform are oriented so that the steep side is toward the central platform. The center of the element has the largest oral surface area to complete the processing of food particles. The central platform is highly ornamented with nodes. These nodes are stretched in the dorso-ventral direction reflecting the motion of the two opposed elements.