Females: P4 Exp2 has leaf-like spines. More characters can be accessed by backtracking the key:
It is very difficult to distinguish between Paracalanus aculeatus, Paracalanus campaneri and Paracalanus denudatus. Bjørnberg (1980) refers to the difference in the shape of the receptaculum seminis in P. campaneri and P. aculeatus as the main difference between these two species.
Males: Right P5 extending as far as proximal third of left leg segment 3. More characters can be accessed by backtracking the key: