Evolutionary patterns in Late Pennsylvanian conodonts

Abstract

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.