Abstract Late Pennsylvanian conodont faunas were dominated by idiognathodids historically assigned to Idiognathodus (flat P 1 ) or Streptognathodus (troughed P 1 ). Recent work suggests clades arose iteratively, through time, from unrelated ancestors in different geographical regions. The end-Desmoinesian extinction event terminated two major genera, Swadelina (troughed) and Neognathodus (long carina), and comparable new morphotypes developed from surviving Idiognathodus species in the early Kasimovian, especially in North America. True Streptognathodus (troughed) and Heckelina n. gen (asymmetric, eccentric groove) appeared in North America in the mid-Kasimovian. Another troughed clade arose in Eurasia (‘ S. ’ 2) and attained a global distribution by the late Kasimovian. A second, early Gzhelian, Eurasian radiation produced new troughed forms (‘ S. ’ 4) that dominated Gzhelian faunas globally. In South China, endemic clades of eccentrically grooved Idiognathodus ? and troughed forms (‘ S .’ 3) appeared in the late Kasimovian and persisted into the Gzhelian. Typical Idiognathodus species were uncommon by the late Kasimovian and disappeared in the mid-Gzhelian. After a low diversity interval in the mid-Gzhelian, a new major radiation of weakly troughed forms occurred (‘ S. ’ 5), which led to redevelopment of Idiognathodus -like elements in the Cisuralian. Other conodont genera from offshore ( Gondolella, Idioprioniodus ) and nearshore settings ( Hindeodus, Diplognathodus, Adetognathus, Ellisonia ) are poorly studied and show low diversity and little morphological change.

Abstract Carboniferous conodont biostratigraphy comprises regional zonations that reflect the palaeogeographical distribution of taxa and distinct shallow-water and deep-water conodont biofacies. Some species have a global distribution and can effect high quality correlations. These taxa are incorporated into definitions of global Carboniferous chronostratigraphic units. A standard global Carboniferous zonation has not been developed. The lowermost Mississippian is zoned by Siphonodella species, excepet in shallow-water facies, where other polygnathids are used. Gnathodus species radiated during the Tournaisian and are used to define many Mississippian zones. A late Tournaisian maximum in diversity, characterized by short-lived genera, was followed by lower diversity faunas of Gnathodus species and carminate genera through the Visean and Serpukhovian. By the late Visean and Serpukhovian, Lochriea provides better biostratigraphic resolution. Shallow-water zonations based on Cavusgnathus and Mestognathus are difficult to correlate. An extinction event near the base of the Pennsylvanian was followed by the appearance of new gnathodid genera: Rhachistognathus , Declinognathodus , Neognathodus , Idiognathoides and Idiognathodus . By the middle of the Moscovian, few genera remained: Idiognathodus , Neognathodus and Swadelina. During the middle Kasimovian and Gzhelian, only Idiognathodus and Streptognathodus species were common. Near the end of the Gzhelian, a rediversification of Streptognathodus species extended into the Cisuralian.

Abstract: The “Wolfcamp Shale” of the Permian Basin in west Texas is a prime source of oil reserves within the USA. Despite its growing importance, definitive ages and stratigraphic correlations across the basin remain unclear. Fusulinid studies have assigned an approximate age of Late Pennsylvanian (Missourian) to early Permian (Leonardian) for the “Wolfcamp Shale,” but exact horizons for regional stage boundaries are not well defined. Analysis of conodont specimens from three cored basinal shale intervals of the Shell Stevens L1V well in the northern part of the Midland Basin (Lynn County, Texas) improves interpretation of regional stage boundaries within the “Wolfcamp Shale” and provides an accurate means of correlation to depositional cycles on the Eastern Shelf in central Texas. Conodont biostratigraphic markers were compared to log correlations and sequence stratigraphic correlations. Associated gamma-ray (GR) and resistivity (RES) logs show distinct log markers for the Pennsylvanian–Permian boundary and base of the Leonardian Stage that are traceable to immediately adjacent wells and possibly to portions of the southern part of the Midland Basin. Third- and fourth-order sequence stratigraphic cycles were delineated using core lithology, conodont abundances, and gamma-ray and resistivity readings. These sequences are linked to those observed in the Eastern Shelf stratigraphic sections and provide a useful secondary mode of correlation.

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