[6] There have been disputes throughout history about whether the two geographically distant populations were truly of the same species, beginning with Milne-Edwards' initial identification in 1837.

[4] With the ambiguous nature of this identification, in the following century, a series of further research comparing specimens from both New Zealand and Chile would introduce competing perspectives, specifically due to a small anatomical discrepancy.

[7][8] Mary J. Rathbun was the first to compare specimens from New Zealand and Chile and support the traditional view of a single species in 1918.

[5] Males will also grow for longer, faster, and larger than females, potentially up to twice the initial mature size.

[4] Males and females are quite similar in appearance, both having a circular carapace that is slightly wider than it is long from the dorsal view.

[4] Small granules, or protrusions, can be seen on the shell from the ventral view towards the front of the crab.

Male appendages tend to be more pilose (hairy) at the base of the claws and along the lengths of the legs.

[3] Variations to this cross-sex positioning of granules and lobes was used in some arguments against the crabs from New Zealand and Chile being the same species.

[3] In the intertidal, there are rarely any below the low-water mark, although female crabs predominate at the lower levels.