Length to 10 mm. Head moderately shorter than in Eupronoe minuta, higher than long and equal to pereonites I-V in females, narrowing distally, longer than high (subequal to pereonites I-VI) in males (Eupronoe armata 1). ART 4 of P I with very short distal process (Eupronoe armata 2); ART 5 narrowing distally, without significant distal processes, shorter than ART 6. Posterodistal process of ART 5 of P II broadly triangular, with rounded top, shorter than ART 6 (Eupronoe armata 3). ART 2 of P V twice as long as broad, with 5-7 denticles on distal part of anterior margin. ART 2 of P VI 1.5 times as long as distal ART combined; ART 5 with short but clearly defined, rounded, anterodistal process; anterior margins of ART 4-6 serrate. Telson triangular, with rounded top.
Usually (accepted herein) Eupronoe intermedia Stebbing, 1888 considered to be junior synonym of Eupronoe armata, though some authors still treat them as separate species (Tashiro, 1978; Zeidler, 1992). The two forms differ as follows: E. armata - head in males slightly produced in lateral view, rounded in dorsal view, ART 2 of P I without distal lobes, ART 2 of P V slightly concave anteriorly in both sexes, distal rudimentary ART of P VII almost circular; E. intermedia - not longer than 6 mm, head ending in small beak, male head triangular in dorsal view, ART 2 of P I with small anterodistal rounded lobe, ART 2 of P V convex in females, slightly concave or straight in males, distal rudimentary ART of P VII elongate (Eupronoe armata 4). Both forms - or species - present in the South Atlantic.