AMORPHOGNATHUS TVAERENSIS FROM THE UPPER SANDBIAN WOMBLE SHALE, BLACK KNOB RIDGE, OKLAHOMA USA

Conodont are a useful tools used for the correlation of Ordovician rocks. The recognition of a new species of Amorphognathus from the upper Sandbian in Estonia resulted in a revised Atlantic Realm Conodont Zone succession proposed for the Baltic area. The new species, A. viirae, described from elements collected from an Estonian drill core is diagnosed by a pronounced sinuous curve on the main denticle row of the dextral Pa element. Amorphognathus tvaerensis from the upper Sandbian Womble Shale at Black Knob Ridge, Oklahoma USA (Katian GSSP section) was questionably synonymized with A. viirae by Paiste et al. (2022). Samples from the Womble Shale at Black Knob Ridge preserve conodont elements in exceptional detail through moldic preservation. Dextral Pa elements of Amorphognathus from the Womble Shale at Black Knob Ridge were studied and compared with the images of dextral Pa elements of A. viirae from the Estonian drill core. No pronounced sinuous curve was clearly and definitively exhibited in the Black Knob Ridge samples of Amorphognathus. The upper Sandbian Amorphognathus elements from the Womble Shale are identified as Amorphognathus tvaerensis. Therefore, the newly proposed Atlantic Realm Conodont Zone succession is not recognized at Black Knob Ridge. More information from additional sections is needed to assess whether the newly proposed Atlantic Realm Conodont Zone succession is recognizable in other Laurentian successions.