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Tarphycerids were the first
Tarphycerids were the first coiled cephalopods, a condition that evolved again in the [[Nautilida]] and [[Ammonoidea]] and in a lesser but more diverse manner in the [[Oncocerida]]. The evolutionary sequence began with an exogastric form like Basslerocers, in which at some early stage the curvature continued beyond the basic arc and eventually grew for more than one volution, producing an open spiraled gyrocone. Here we have the first undeniable tarphycerid. A similar sequence can be shown form the nautilids and for the ammonoids.