Dactylus

Definition
noun, plural: dactyla
(zooanatomy) A dactyl, i.e. a digit (a finger or a toe)
Supplement
The term dactylus refers to a dactyl, which in turn pertains to a digit (i.e. a finger or a toe) of humans, or that which corresponds in other vertebrates. Etymologically, it comes from the Greek word that means finger or dactyl.
In invertebrates, the term dactylus is used to refer to the tip region of the tentacular club of cephalopods (e.g. squid and octopus). The dactylus of the cephalods is narrow. It may be identified by the asymmetrical placement of suckers and the lack of a dorsal protective membrane.¹
Dactylus may also pertain to the leg of a decapod crustacean. The leg of crustacean is comprised of seven segments. In their proper order, the segments are named coxa, basis, ischium, merus, carpus, prodopus, and dactylus. Other crustaceans, though, do not conform to this naming system. The dactylus is the seventh (final) segment of thoracic appendages of crustaceans. In certain crustaceans, the dactylus and an outgrowth of the propodus may be fused, forming the claw.²
Word origin: Greek dáktulos (“a finger, a dactyl”)
See also:

• dactyl

Reference(s):

¹ Dactylus. (n.d.). Retrieved from https://en.wikipedia.org/wiki/Dactylus

² Arthropod leg. (n.d.). Retrieved from https://en.wikipedia.org/wiki/Arthropod-leg