The mid-Ordovician noticed the initial cephalopods with septa solid plenty of to manage Along with the pressures connected to deeper water, and will inhabit depths bigger than one hundred200 m.[139] The route of shell coiling would demonstrate to become crucial to the longer term results on the lineages; Squid endogastric coiling would only permit large sizing being attained by using a straight shell, whereas exogastric coiling in the beginning somewhat