Ctenopteryx the Comb-Fin Squid is Related to Loligo

Ctenopteryx shows a combination of unique features with others that are found only in loliginids and Pickfordiaeuthis. The fins differ superficially from those of other cephalopods and are here fully described for the first time. Their muscles are largely reduced to a series of hydro-muscular rays, but these may operate on the same principle as in other squids. The affinity with loliginids is shown by several characters and especially by the fusion of nerve axons in the giant fiber system. Ctenopteryx has thus evolved in many ways on its own line but it shares distinctive characters with loliginids, as was shrewdly noticed by Naef in 1921. It should be classified nearer to them than to other teuthoids, perhaps in the suborder Myopsida (although the eye chamber is open). Ctenopteryx is cosmopolitan but it is not clear what niche its fins and other special features enable it to occupy in the mesopelagic to bathypelagic zones. It may be considered as a teuthoid related to loliginids, which has become adapted to deep water.