The mid-Ordovician observed the initial cephalopods with septa robust adequate to cope While using the pressures connected to further water, and will inhabit depths increased than 100200 m.[139] The way of shell coiling would confirm for being crucial to more the longer term good results of the lineages; endogastric coiling would only allow huge size being attained using a straight shell, whereas exogastric coiling to begin with instead