• (n.) The basal portion, or two proximal and more or less consolidated segments, of an appendage of a crustacean.
(from the article `crustacean`) ...derived either from the multibranched (multiramous) limb of the class Cephalocarida or from the double-branched (biramous) limb of the class ...
Pro·top'o·dite noun [ Proto- + Greek ..., ..., foot.] (Zoology) The basal portion, or two proximal and more or less consolidated segments, of an appendage of a crustacean. 
the basal portion of a two-branched crustacean leg or other appendage.