INSIGHTS INTO AMORPHOGNATHUS PALEOBIOLOGY AND TAXONOMY FROM BEDDING PLANE OCCURRENCES OF A. TVAERENSIS

Conodonts preserved on bedding surfaces provide paleobiological and taxonomic information that is either difficult or impossible to obtain from isolated elements freed from rocks. Element position in the apparatus, number of elements, and number of element types in an apparatus are the types of information typically gathered from bedding plane assemblages. Dark shale surfaces from the Late Ordovician in Oklahoma and Idaho contain both isolated and apparatus associations of Amorphognathus tvaerensis. One nearly complete bedding plane association of A. tvaerensis from Phi Kappa Formation in Idaho illustrates relative position of the elements in the feeding apparatus. Unfortunately, the state of preservation is not adequate for an unequivocal understanding of the number of elements in the apparatus. Individual elements of A. tvaerensis demonstrate that the posterior process in ramiform S elements were likely flexible, and that some extended nearly a centimeter in length. Posterior bars of elements appear not to have been mineralized throughout their entire length, and when these elements are processed out of rocks, portions of the bars, which have small basal cavities, are easily mistaken for complete elements. Bedding plane Amorphognathus elements from the Phi Kappa Formation and the Womble Shale support the idea that many isolated elements identified as Eocarniodus are portions of Amorphognathus elements.