Abrupt changes in distance between succeeding septa at the hatching time in modern coleoids Sepiella japonica and Spirula spirula Ayaka Yamaguchi, Yuichiro Kumada, Andrea C. Alfaro, Ryoji Wani 2015 (subscription)
Analyses of distances between succeeding septa throughout ontogeny of modern coleoids Sepiella japonica and Spirula spirula reveal that the first several septa (until ca. 6th–8th septa in Sepiella japonica and until ca. 2nd–3rd septa in Spirula spirula) have relatively larger septal distances than the following septa and then the distances between succeeding septa abruptly decrease at the time of hatching for both species, which are known from previous rearing observations and stable isotopic analyses. If this relationship holds in fossil cephalopods preserving internal shells, their paleo-hatching timings could be reconstructed through the ontogenetic analyses of their septal distances.