The Gasconadian is named for the Gasconade Formation of Missouri, named in turn for the Gasconade River, and is represented by the Tribes Hill Formation in New York state and by the upper Bliss Fm and the Sierrite Ls of the El Paso Group in southern New Mexico and west Texas.
The Bliss is a near shore, deltaic, and beach sandstone deposit; the lower part spans the Upper Cambrian.
Among these were Clarkoceras and Ectenolites which continued from the Late Cambrian, along with the exclusively Ordovician Ellesmeroceras the similar Eremoceras, both cylindrically orthoconic, and the compressed endogastirc Dakeoceras.
All have essentially straight, short septal necks and thick concave connecting rings in the siphuncle.
The latter Canadian, following the Gasconadian saw the onset and early diversification of two new orders, the Endocerida and Tarphycerida, evolution of new families within the Ellerocerida (e.g. Baltoceratidae and Bathmoceratidae), and near the end the first of the Orthocerida, Actinocerida, and Discosorida.