Order SEPIOLIDA Fioroni, 1981

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Regional Maps

• SEPIOLIDA Fioroni, 1981.

Introduction

The Sepiolida is very diverse, and comprises the families Sepiadariidae (with two genera and five nominal Australian species); the Sepiolidae that includes the benthic Sepiolinae (with five genera and seven species); the pelagic Heteroteuthinae (three genera and five species in Australian waters) and the benthic Rossinae with two genera, each with a single species. While diverse, the monophyly of the Sepiolida has been supported in numerous studies, including the comprehensive molecular studies of Fernandez-Alvarez et al. (2021) and Sanchez et al. (2021).

Ecological Descriptors

Marine.

Diagnosis

Mantle oval with posterior end widely rounded or elongate with posterior end slightly narrowed and bluntly pointed. Ten appendages present: 4 pairs of arms and one pair of tentacles. Tentacular stalks retractile, but not retracted into special pockets at bases of tentacles. Suckers stalked, with chitinous ring usually having the edge denticulate; ring never modified into a hook. Arms connected by webs and in some, web between 3rd and 4th arms envelops tentacle bases on outside only, without forming sac. Fins always present, variable; oval or kidney-shaped, located in middle or somewhat posterior of middle of mantle or near posterior end, not joined posteriorly. Anterior edge of mantle may or may not be fused with head dorsally. Nuchal, mantle, and funnel cartilages usually present except where mantle and head fused dorsally. Funnel cartilages simple; mantle edge near mantle cartilages straight, without protruding 'angles'. Shell either a thin chitinous vestige or absent altogether. Hectocotylisation variable: both dorsal arms or one ventral arm hectocotylised, sometimes lateral arm pairs also modified; in some species hectocotylisation is almost inconspicuous. Oviduct unpaired, accessory nidamental glands present. All radular teeth unicuspid or multicuspid (as in Idiosepius).

General References

Fernandez-Alvarez, F.A. Sanchez, P. & Villanueva, R. 2021. Morphological and molecular assessments of bobtail squids (Cephalopoda: Sepiolidae) reveal a hidden history of biodiversity. Frontiers of Marine Science 7(632261)

Sanchez, G. Fernandez-Alvarez, F.A. Tait, M. Sugimoto, C. Jolly, J. Simakov, O. Marletaz, F. Allcock, L. & Rokhsar, D.S. 2021. Phylogenomics illuminates the evolution of bobtail and bottletail squid (order Sepiolida). Communications Biology 4(819): 1-9

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