dactylus

{{short description|Body part of cephalopods and some crustaceans}}

{{About||the foot in metric poetry|Dactyl (poetry)|the suffix "-dactylus"|List of commonly used taxonomic affixes}}

Image:Crustaceanleg.jpg, with the dactylus labelled]]

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){{cite web |last1=Walla |first1=Graeme |title=Comparative Morphology of Cephalopod Armature |url=https://tonmo.com/articles/comparative-morphology-of-cephalopod-armature.27/ |website=The Octopus News Magazine Online |access-date=2 February 2024}} 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.{{cite journal |last1=Robin |first1=Ninon |last2=van Bakel |first2=Barry W. M. |last3=Hyžný |first3=Matúš |last4=Cincotta |first4=Aude |last5=Garcia |first5=Géraldine |last6=Charbonnier |first6=Sylvain |last7=Godefroit |first7=Pascal |last8=Valentin |first8=Xavier |title=The oldest freshwater crabs: claws on dinosaur bones |journal=Scientific Reports |date=27 December 2019 |volume=9 |issue=1 |pages=20220 |doi=10.1038/s41598-019-56180-w |pmid=31882600 |language=en |issn=2045-2322|pmc=6934782 |bibcode=2019NatSR...920220R }}

The term dactylus means "finger" in Greek.