Dactylus

For the foot in metric poetry, see Dactyl (poetry). For the suffix "-dactylus", see List of commonly used taxonomic affixes.

The dactylus is the tip region of the tentacular club of cephalopods and of the leg of some crustaceans (see arthropod leg). In cephalopods, the dactylus is narrow and often characterized by the asymmetrical placement of suckers (i.e., the ventral expansion of the club) and the absence of a dorsal protective membrane. In crustaceans, the dactylus is the seventh and terminal segment of their thoracic appendages. In certain instances the dactylus, together with the propodus, form the claw.

The term dactylus means "finger" in Greek.

References

Cephalopod anatomy

Shell

Shell types	External shells: Ammonoid shell Argonautid eggcase Nautiloid shell Orthocone Internal shells: Belemnoid guard Cirrate shell Cuttlebone Gladius (pen) Spirula shell Stylet

External features	Aperture Apex Callus Lirae Periostracum Sculpture Spire Sutures Umbilicus

Internal features	Body chamber Camerae Nacre Phragmocone Septa Siphuncle Whorls

Mantle

External anatomy	Funnel Dermal structures Fins (wings) Mantle locking-apparatus

Internal anatomy	Branchial hearts Ctenidia (gills) Hepatopancreas (digestive gland) Ink sac and ink Needham's sac Nephridia ("kidneys") Nidamental glands Osphradium Pericardial glands

Head and limbs

Brachial crown	Arms Hectocotylus Tentacles

Buccal region	Aptychus Beak Odontophore Radula Spadix and antispadix

Other parts	Eyes Statocysts

General

Chromatophores
Photophores
Nervous system
- Squid giant axon
- Squid giant synapse

Developmental stages: Spawn → Paralarva (Doratopsis stage) → Juvenile → Subadult → Adult • Egg fossils • Protoconch (embryonic shell)

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