Early Ordovician conodonts from the Horn Valley Siltstone, central Australia

Conodonts from the early Ordovician Horn Valley Siltstone in the Amadeus Basin, Northern Territory, Australia, are described and illustrated. Samples were collected from limestone beds within the unit at two easily accessible localities. Twenty-two multi-element species belonging to seventeen genera are described. One new genus (Jumudontus) and eight new species (Acodus buetefueri, Drepanoistodus pitjanti, Erraticodon patu, Jumudontus gananda, Prioniodus amadeus, Protoprioniodus aranda, Protoprioniodus nyinti, and Protoprioniodus vapu) are proposed. The report also constitutes a revision of a small conodont collection described by Crespin (1943). The Horn Valley conodonts are mid Arenig in age. They correlate with conodont zones OCD and OCE of the Canning Basin, north-west Australia, and relate to faunas from the Oepikodus evae and Baltoniodus triangularisj Baltoniodus navis Zones on the Baltic Platform. In North America the Horn Valley conodonts are equivalent to late Fauna E, Fauna 1, and early Fauna 2 of the Midcontinent succession, thus indicating an uppermost Canadian and early Whiterock age.