The mid-Ordovician noticed the main cephalopods with septa solid adequate to cope Along with the pressures linked to deeper drinking water, and could inhabit depths larger than 100200 m.[139] The course of shell coiling would demonstrate to be critical to the future results from the lineages; endogastric coiling here would only allow big sizing for being attained which has a straight shell, whereas exogastric coiling to begin with instead