MOTS CLÉSChordata, Craniata, animal-conodonte, codage des caractères, analyse cladistique, paléohistologie. KEY WORDSChordata, Craniata, conodont animals/ elements, character coding, cladistic analysis, palaeo-histology. ABSTRACTAn evidence-based reassessment of the phylogenetic relationships of conodonts shows that they are not "stem" gnathostomes, nor vertebrates, and not even craniates. A signifi cant group of conodont workers have proposed or accepted a craniate designation for the conodont animal, an interpretation that is increasingly becoming established as accepted "fact". Against this prevailing trend, our conclusion is based on a revised analysis of traditional morphological features of both discrete conodont elements and apparatuses, histological investigation and a revised cladistic analysis modifying that used in the keystone publication promoted as proof of the hypothesis that conodonts are vertebrates. Our study suggests that conodonts possibly were not even chordates but demonstration of this is beyond the scope of this paper. To summarize, in conodonts there is low cephalization; presence of simple V-shaped trunk musculature and unique large-crystal albid material in the elements; lack of a dermal skeleton including characteristic vertebrate hard tissues of bone, dentine and enamel; lack of odontodes with bone of attachment and a unique pulp system; lack of segmentally-arranged paraxial elements and dermal elements in median fi ns, all of which supports neither a vertebrate nor a craniate relationship for conodonts. RÉSUMÉ Des pseudo-dents : une réévaluation des relations phylogénétiques des conodontes et des vertébrés.Une réévaluation des relations phylogénétiques des conodontes est fondée sur de nouvelles preuves. Elle montre que les conodontes ne sont ni des gnathostomes-souches, ni des vertébrés, ni même des crâniates. Un groupe signifi catif de spécialistes des conodontes a proposé, ou accepté, que ces organismes soient considérés comme des crâniates, une interprétation qui est en train de s'installer en tant que fait avéré. Notre conclusion va à l'encontre de cette tendance ; elle est fondée sur une révision des traits morphologiques traditionnels à la fois des éléments isolés et des assemblages de conodontes, sur les données histologiques et sur une analyse cladistique révisée, ce qui modifi e les conclusions de la publication principale qui a promu l'hypothèse selon laquelle les conodontes seraient des vertébrés. Notre étude suggère même que les conodontes n'aient pas été des chordés, mais la démonstration de cette hypothèse va au-delà de l'objectif de cet article. En résumé, chez les conodontes, le degré de céphalisation est faible ; la musculature du tronc a une forme simple en V ; les éléments isolés montrent un tissu blanc avec des cristaux de grande taille, uniques pour ce tissu ; il n'y a pas de squelette dermique incluant les tissus durs caractéristiques des vertébrés tels que l'os, la dentine et l'émail ; il n'y a pas d'odontodes avec leur os et leur système pulpaire unique ; il ...

The Providence Limestone member of the Dugger Formation in Indiana and its lithologic correlatives in the southern part of the Illinois Basin are thin lime mudstones to packstones lying stratigraphically between the Herrin and Hymera Coal Members of the Dugger Formation and their equivalents. The purposes of the study are to describe and correlate the Providence conodont fauna and to apply biofacies analysis and petrographic study to interpreting the paleoenvironments.Providence conodonts are dominated by representatives of the Idiognathodus-Streptognathodus plexus. Hindeodus is abundant; Neognathodus is common; and Idioprioniodus, Adetognathus, and Diplognathodus are common only in some sections. Aethotaxis is a minor constituent.Conodont biofacies reflect a shallow, nearshore, low- to moderate-energy marine environment. The Idiognathodus-Streptognathodus plexus indicates quiet to moderately elevated energy levels. Hindeodus replaces part of the Idiognathodus-Streptognathodus plexus in higher energy conditions. Diplognathodus has an affinity for low to slightly elevated energy conditions. Migration during ontogeny to quite, organic-rich water from a more open, slightly higher energy environment is indicated for Streptognathodus oppletus.Assignment to the Neognathodus dilatus-N. roundyi zone indicates a middle Desmoinesian age. The new species Diplognathodus indianaensis is morphologically intermediate between the early Desmoinesian D. coloradoensis and the late Desmoinesian D. illinoisensis and allows refinement of a Diplognathodus-based zonation.

More than 20 characteristic conodont faunas have been recognized in North American Mississippian rocks. Although best known in the Mississippi Valley and southwestern Missouri, they are widespread on the continent.Six zones and four subzones in the Kinderhookian Series are based on lineages of Siphonodella and Gnathodus. A succession of primitive gnathodids in the lowermost part of the series-Protognathodus meischneri, P. kockeli and P. kuehni-matches that in the lower part of the Gattendorfia-Stufe in Germany.The occurrence of Gnathodus punctatus in Missouri, Oklahoma and Arkansas identifies the youngest Kinderhookian and protably correlates with the lower part of the German Pericyclus-Stufe, and with the middle part of the Zaphrentis Zone of the British Avonian. Significant differences are found in the ranges of siphonodellid and gnathodid species in western Europe and America. Several species found together abroad are stratigraphically separate in the central United States. 353 on May 26, 2015 memoirs.gsapubs.org Downloaded from 354 SYMPOSIUM ON CONODONT BIOSTRATIGRAPHY