The mid-Ordovician saw the initial cephalopods with septa sturdy plenty of to manage Along with the pressures connected to further water, and could inhabit depths bigger than a hundred200 m.[139] The route of shell coiling would demonstrate for being Squid essential to the future achievements with the lineages; endogastric coiling would only permit big sizing being attained by using a straight shell, whereas exogastric coiling in the beginning somewhat