Order SEPIIDA

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Introduction

Members of the order Sepiida are mesopelagic or benthic, and include the oceanic ram's horn shell, Spirulidae, the benthic cuttlefishes, Sepiidae, and the bottletailed squid Sepiadariidae.

Diagnosis

Mantle either not fused or fused with head at occipital area and regions of mantle and funnel cartilages. Nuchal, mantle, and funnel cartilages present unless fused with head. Ten appendages: 4 pairs of arms and one pair of tentacles. Tentacular stalks retractile, may be retracted into special pockets at bases of tentacles. Arms and tentacles armed only with stalked suckers; suckers with a chitinous ring that is usually denticulate on edge; ring never modified into a hook. Arms short, with shallow or broad web or without web. Fins always present and not connected posteriorly, oval or kidney-shaped, situated on sides of body or near posterior end or extend laterally along entire mantle in form of marginal fin. Hectocotylisation may or may not be present; when present, left ventral arm or both ventral arms are modified. Shell either a calcareous plate, calcareous spiral or absent. Oviduct unpaired, accessory nidamental glands present. All radular teeth unicuspid, or radula absent.

General References

Lu, C.C. 2001. Cephalopoda. pp. 129-308 in Wells, A. & Houston, W.W.K. (eds). Zoological Catalogue of Australia. Vol. 17.2 Mollusca: Aplacophora, Polyplacophora, Scaphopoda, Cephalopoda. Melbourne : CSIRO Publishing, Australia xii 353 pp. [Date published 3 July 2001]

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