Based on sequential growth stages of Moroteuthis robusta, M. japonica and M. pacifica are synonymous with M. robusta, and smaller stages are bridged to the Onykia “carribaea” species complex. Within the family Onychoteuthidae, the genus Onykia
has in common with the genus Moroteuthis the absence of both visceral photophores and dorsal nuchal folds. Young Moroteuthis have a smooth mantle surface with a distinct iridescence, a small number of marginal suckers on the tentacular club and an indistinct cartilageous cap
on the endocone. While, large Onykia develop rhomboidal fins, an inverted Y-shaped cartilageous ridge in the funnel groove, and a reduced number of marginal suckers on the club, all of which characterize Moroteuthis. Close examination of a series of O. “carribaea”
specimens reveals that the species is not monospecific, but contains more than one species. It is thus suggested that the genus Onykia, therefore, appears to represent juvenile stages of the genus Moroteuthis.
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