 Tarphycerida

The Tarphycerida were the first of the coiled cephalopods, found in marine sediments from the Lower Ordovician (middle and upper Canad) to the Middle Devonian.Some, such as "Aphetoceras" and "Estonioceras", are loosely coiled and gyroconic; others, such as "Campbelloceras", "Tarphyceras", and "Trocholites", are tightly coiled, but evolute with all whorls showing.