The mid-Ordovician observed the initial cephalopods with septa robust adequate to cope While using the pressures connected to deeper water, and will inhabit depths better than 100200 m.[139] The way of shell coiling would confirm for being crucial to the longer here term good results of the lineages; endogastric coiling would only allow huge sizing to get attained having a straight shell, Whilst exogastric coiling originally rather