 The body chamber of tarphycerids is typically long and tubular, as much as half the length of the containing whorl in most, greater than in the Silurian Ophidioceratidae.The Tarphycerida evolved from the elongated, compressed, exogastric Bassleroceratidae, probably "Bassleroceras", around the end of the Gasconadian through forms like "Aphetoceras".Close coiling developed rather quickly, and both gyroconic and evolute forms are found in the early middle Canadian.