CHEMICAL ELEMENT DISTRIBUTIONS IN CONODONT TEETH

Many studies now support the interpretation that the conodont animal was an active, marine vertebrate with oral phosphatic structures, large eyes, and fins for swimming. Studies of mineral composition, histology, and morphology in conodont teeth provide important information on biologic function and taxonomic affinity. This study utilizes advances in modern instrumentation to precisely map variations in elemental abundance across conodont teeth for the purpose of identifying function and assisting paleobiologic interpretations. Electron microprobe analysis of well-preserved P1 elements of Mesogondolella idahoensis lamberti from the Lower-Middle Permian boundary of West Texas reveals important patterns in element distributions. The crown of the conodont tooth is more mineralized than the basal plate and shows no evidence of calcium or phosphate deficiency in areas of rapid lateral growth that might have been interpreted as white matter. Additionally, the basal plate has higher concentrations of fluorine, iron, potassium, magnesium, strontium, and yttrium, which indicate a different mineral structure and composition. Sodium concentrations are high on oral surfaces in the crown between the parapets and low elsewhere while sulfur concentrations display the opposite pattern. These patterns are independent of the crown-basal plate boundary and indicate chemical differentiation between the oral and aboral surfaces in conodont teeth. This differentiation supports oral exposure of conodont teeth during life, approximates the position at which conodont teeth was embedded in tissue, and indicates functional use as a tooth as opposed to a support structure for soft tissue. These variations in chemical composition support previously interpreted histologic properties of the crown and the basal plate that indicate similarity to enamel and dentine respectively. The variations in calcium, phosphorous, sodium, sulfur, magnesium, and strontium are also comparable to those in modern mammal teeth. Diagenetic studies on 3.9Ma mammal teeth indicate that strontium, magnesium, and sodium are relatively stable elements and do not get significantly enhanced during diagenesis. Accordingly, conodont elements should henceforth be called conodont teeth.