The species was first described by Dutch zoologist Dr. Paulus Peronius Cato Hoek after his voyage on the HMS Challenger from 1873-1876.

[1] Colossendeidae exhibit apomorphies such as cephalization through the anterior migration of trunk ganglia and loss of chelifores.

[5] Further speciation of C. Megalonyx has been proposed due to its high morphological variability and wide distribution.

[6] Colossendeis megalonyx is characterized by its long proboscis, reaching up to about twice its trunk size as an adult.

C. megalonyx's ovigers are unique as the distal articles, also known as strigilis, have six rows of compound spines specialized for cleaning.

C. megalonyx captures prey within its leg span by bending and striking with the tip of its proboscis.

[14] Colossendeis megalonyx utilises its porous cuticle and large surface area-to-volume ratio to absorb oxygen and efficiently release carbon dioxide via diffusion.

This high porosity may allow C. megalonyx to grow to larger sizes and be more mobile and active than its related species.

[18] Divers have observed Colossendeids stacked on top of each other in groups of 2-4, similar to mating postures exhibited by other pycnogonids.

[20] They housed the mating groups in a flow-through seawater system, checking them for eggs several times daily.