Abyssorchomene abyssorum

<div><p>Key to the species of the Abyssorchomene abyssorum complex</p> <p>1. Pereonites 1–7 and pleonites 1–2 with weak but distinct dorsoposterior rounded hump; epistome level with upper lip; uropod 3 inner ramus extends well past distal end of article 1 of uropod 3 outer ramus; maxilla 1 palp distal end weakly convex, with distal spines contiguous............................... 2</p> <p>– Pereonites 1–7 and pleonites 1–2 lacking dorsoposterior rounded hump; epistome weakly but distinctly protruding in front of upper lip (or level with upper lip); uropod 3 inner ramus just reaches (or very slightly exceeds) distal end of article 1 of uropod 3 outer ramus; maxilla 1 palp distal end strongly convex, with distal spines not contiguous.......................................... A. scotianensis (Andres, 1983)</p> <p>2. Coxa 1 slightly widened distally, ~ 1.2× proximal width; gnathopod 2 propodus of female narrow, (similar in form to male), length ~ 2.5× width, palm lacking concavity; uropod 3 inner ramus extends to ~ 70% of the length of article 2 of uropod 3 outer ramus.............. A. abyssorum (Stebbing, 1888)</p> <p>– Coxa 1 strongly widened distally, ~ 1.3–1.7× proximal width; gnathopod 2 propodus of female broad, (different in form to narrow male propod), length <2 × width, palm with small concavity; uropod 3 inner ramus extends to 63% or less of the length of article 2 of uropod 3 outer ramus.................... 3</p> <p>3. Coxa 5 posteroventral lobe broadly rounded, posterior margin evenly rounded; lateral head lobe, dorsal and ventral margins similar; gnathopod 2 propodus of female with anterodistal margin broadly expanded and protruding, dactylus tiny, inserted near the bottom of the distal margin; gnathopod 2 propod of male slightly expanded anteriorly; pereopod 7 basis posteroventral corner steeply and strongly beveled; uropod 3 inner ramus extends to ~ 20–25% of article 2 of uropod 3 outer ramus................................................................................................................ A. shannonae sp. nov.</p> <p>– Coxa 5 posteroventral lobe narrowly rounded, posterior margin with distinct straight section; lateral head lobe, dorsal margin strongly convex, ventral margin nearly straight with slight concavity at the midpoint; gnathopod 2 propodus of female with anterodistal margin not expanded and protruding, dactylus large, inserted at the top of the distal margin; gnathopod 2 propod of male not expanded, narrow, dorsal margin smoothly convex; pereopod 7 basis posteroventral corner shallowly and weakly beveled; uropod 3 inner ramus extends to ~ 63% of article 2 of uropod 3 outer ramus................................................................................................................................................... A. patriciae sp. nov.</p></div>