Diagnosis: This medium-sized torpedo ray species has a uniform shiny black to dark gray live dorsal color, and is distinguished from its most similar congeners Tetronarce nobiliana and T. puelcha by the following combination of characters: shorter spiracular length, 1.5-1.6% of total length vs. 2.6-2.8% in T. nobiliana and 2.4-3.1% in T. puelcha; a proportionally greater head length as measured between snout margin and fifth gill openings, 30.5-31.2% of total length vs. 24.7-25.8% in T. nobiliana and 26.8% in adult male T. puelcha; and a proportionally greater preoral snout length, 8.9-9.3% of total length vs. 7.4-7.6% in T. nobiliana and 6.5-8.4% in T. puelcha (Ref. 100734). It is further distinguished from T. nobiliana by its more circular anterior disc shape vs. relatively straight; fewer tooth rows, 32/28 vs. 38/38 in T. nobiliana from the North Sea and up to 53/52 in T. nobiliana from the Mediterranean; greater mouth width, 1.5-1.7 times as great as interorbital width vs. 0.5-0.6 times interorbital width; smaller distance between second dorsal and caudal fins, 3.5-4.9% vs. 6.6-6.8%; and greater clasper length in mature individuals, extending nearly to lower caudal fin origin vs. clasper extends only two-thirds the distance between second dorsal and caudal fins (Ref. 100734).
Description: Disc broadly rounded, anterior margin nearly straight in outline with a slight median protuberance; disc width greater than length; disc width 65.2-69.3% of total length and disc length 55.4-58.9% of total length; disc widest at about one-third its length, and thickest at anterior margin; disc does not overlap origin of pelvic fins, with prominent free posterior lobes broadly rounded; disc fleshy, thick anteriorly, progressively thinning posteriorly (Ref. 100734). Preorbital snout length about 7.0-7.9 times in disc length, 1.8-2.3 times orbit diameter, and slightly greater than prenasal snout length; eyes small, orbital diameter about 2.1-2.7 times spiracle length; eyes and spiracles close together, space between them about equal to interspiracular width; distance between orbits 1.2-1.5 times distance between spiracles; spiracles smooth, lacking papillae, moderately large and hemispherical, opening posteriorly (Ref. 100734). Pseudobranchial folds line anterior margin inside spiracles; pseudobranchial fold number differs between left and right, 13-12 (10-9) (Ref. 100734). Electric organs not clearly visible dorsally, but distinguishable in ventral view; electric organs originate very close to anterior disc margin, anterior to eyes and nostrils, and terminate posteriorly, just past fifth gill slits; electric organs kidney shaped, widest anteriorly between mouth and first gill slit; length of electric organ about 2.0-2.5 times its greatest width; dorsal and ventral skin surfaces entirely smooth (Ref. 100734). Nasal curtain subquadrangular, its width about 2-3 times its length; nasal curtain extends posteriorly in a relatively straight line towards mouth; posterior margin of nasal curtain with two confluent lobes, broadly rounded and angled medially; margin not fringed; posterior margin of nasal curtain with a slight median lobe; outer margins of nostrils situated at level of mouth corners; posterior contour of nostrils confluent with prominent median lobes that contact nasal curtain at corners and separate nostrils from mouth; skin at corners of mouth loose, deeply furrowed; mouth broadly arched with relatively large gape; width greater than internarial width; internarial width about 1.6 times in mouth width; teeth set in quincunx, flattened labial-lingually, morphologically similar in both upper and lower jaws, with well-developed single cusps (Ref. 100734). Gill slits crescent shaped; first gill slits positioned at about one-third of disc length, fifth gill slit situated slightly more than one-half disc length; first four gill slits nearly equal in length, fifth gill length about one-half to two-thirds length of first four; distance between first gill slits slightly greater than distance between fifth gill slits; length of first four gill slits nearly two times spiracle length; fifth gill slit length nearly same as spiracle length (Ref. 100734). Pelvic fins originate just anterior to disc insertion; pelvic fins long, length about one-fifth of total length and about two-thirds of pelvic fin width; anterior margins of pelvics relatively straight, but broadly rounded at apex; pelvic posterior margins more convex; pelvic fins widest at about one-half of their length; pelvic fins much wider than long; length about 62% of width; cloaca situated anterior to one-fifth length from pelvic fin origin (Ref. 100734). Claspers of mature male extend well past insertion of second dorsal fin; claspers of immature specimens do not extend past free rear tips of pelvic fins; claspers of maturing males may extend past pelvic fin tips, but generally do not reach second dorsal fin insertion; claspers dorsoventrally flattened, clasper groove about 80% length of inner clasper length, where it curves medially; dorsal and ventral pseudosiphon slits present; ventral pseudosiphon about one-third greater in length than dorsal pseudosiphon; a fleshy integumental flap covers hypopyle (Ref. 100734). Tail moderately short and stout, 22.1-23.4% of total length as measured from second dorsal fin insertion, but tail length from cloaca 20.4-24.4% of total length; tail tapers from posterior tips of pelvic fins toward caudal fin; tail width about two times greater than height at pelvic tips, but more circular in cross-section at caudal fin origin; lateral tail folds ridgelike, originating below second dorsal fin origin, becoming more prominent along caudal peduncle region, and terminating posterior to dorsal and ventral facets of caudal peduncle; tail-fold origin not as distinguishable as insertion; lateral tail folds vary slightly in length between each side of tail, 11.8-13.3% of total length (Ref. 100734). First dorsal fin broad, subtriangular with rounded corners, and originating just posterior to level of widest pelvic fin width; anterior margin of first dorsal moderately slanted, with posterior free lobe about equal to two-thirds the base length; first dorsal fin base length about two-thirds of its height; less than half of first dorsal fin base situated over pelvic fin bases, but posterior free lobe of first dorsal does not extend posterior to level of pelvic fin tips; first dorsal fin posterior margin ends well anterior to level of second dorsal fin origin in holotype, but posterior in paratype; first dorsal fin about one-third larger than second dorsal; first dorsal fin height about 1.5-1.6 times greater than second dorsal height; first dorsal fin base length 1.5-1.9 times greater than second dorsal base length; dorsal fins somewhat similar in shape, second dorsal fin with lower and more acute apex; interdorsal space about equidistant between second dorsal fin insertion and dorsal caudal origin; caudal fin emarginated, tall and triangular, overall height 22.3-25.5% of total length; upper margin of caudal fin slightly longer, and more sloping, than lower margin; posterior margin of caudal fin slightly concave at about mid-height; apices of caudal fin broadly rounded (Ref. 100734). Tooth row counts in upper jaw 26-32 and lower jaw 26-28; spiral valve counts 14-16 (Ref. 100734).
Colouration: Dorsal surface colour in life is a uniform shiny black or dark gray; ventral surface creamy white; juveniles darker on disc and pelvic fin margins, but fading in adults (Ref. 100734). After preservation dorsal surface fades to a brownish gray (Ref. 100734).