Abstract

Swadelina n. gen. is erected to comprise a short-ranging clade of late Desmoinesian (middle Pennsylvanian) idiognathodontid conodonts characterized by Pa elements with a deep medial trough, extensive anterior ornamentation, and an extremely short carina. The Pb elements have a small, relatively indistinct cusp, and dissimilar development of the anterior and posterior processes. Swadelina (Sw.) probably evolved through paedomorphosis from an untroughed Idiognathodus ancestor well before the appearance of similarly troughed Streptognathodus Pa elements in the Missourian (late Pennsylvanian). We currently recognize Sw. nodocarinata (Jones 1941) and Sw. neoshoensis n. sp. as component species. Swadelina occurs in both North America and Eurasia with a limited range, in strata that are otherwise characterized by pronounced provincialism. With further study of international occurrences, a species of Swadelina may provide for the definition and correlation of an appropriate GSSP stage/series boundary between the middle and upper parts of the Pennsylvanian Subsystem.

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