Sternoptychidae

Lima, Adriano T., Costa, Paulo A. S., Braga, Adriana C., Nunan, Gustavo W. A. & Mincarone, Michael M., 2011, Fishes of the family Sternoptychidae (Stomiiformes) collected on the Brazilian continental slope between 11 ° and 23 ° S, Zootaxa 2742, pp. 34-48 : 44-45

Key to species of Sternoptychidae from the western South Atlantic

(asterisks indicate species not recorded in Brazilian waters)

1a. Body laterally compressed and deep, body depth 1–2 times the SL; dorsal blade moderately to well developed; abdominal keel developed; post-abdominal spines present and sometimes robust ..................................................... 2

1b. Body somewhat elongate, depth more than 3.5 times the SL; dorsal blade, abdominal keel, and post-abdominal spine absent or inconspicuous ............................................................................................................................................. 10

2a. Dorsal blade consisting of several spines; eyes tubular and directed dorsally; AB 12 ................. ( Argyropelecus )... 3

2b. Dorsal blade consisting of one or two spines; eyes not tubular and directed laterally; AB 10 ................................... 7

3a. PAN, AN, and SC series not distinctly separated, photophores of each series not sharing common photogenic mass, and all three series on about same level as SAB; anal-fin rays not divided by central AN ......................................... 4

3b. PAN, AN, and SC in distinct groups, all three series elevated with respect to SAB; anal-fin rays divided into anterior and posterior groups by central AN ............................................................................................................................. 5

4a. Dorsal blade reduced, its height less than one third of its length; body profile without elevation between third and

fourth fused spines of dorsal blade and posterior of dorsal blade; adults without postorbital spine; snout with evenly convex profile ............................................................................................................................... Argyropelecus affinis 4b. Dorsal blade developed, its depth greater than one third of its length; body profile with fleshy elevations between third and fourth fused spines of dorsal blade and posterior to dorsal blade; adults with distinct postorbital spine; snout with angular profile ............................................................................................................ Argyropelecus gigas *

5a. A single, serrated, posteriorly directed postabdominal spine; length of AN photophore series less than length of gap between AN and SC photophores; dorsal-fin rays 8; anal-fin with 6 rays in the anterior group, 5 rays in posterior group ................................................................................................................................... Argyropelecus hemigymnus

5b. Two smooth post-abdominal spines, one directed posteroventrally and the other directed anteroventrally; length of AN photophore series greater than length of gap between AN and SC photophores; dorsal-fin rays 9 or 10; anal-fin with 7 rays in anterior group, 5 rays in posterior group................................................................................................ 6

6a. Lower jaw with prominent canine teeth; posterior post-abdominal spine much larger than anterior spine, directed posteroventrally; SC photophore scales with long, spine-like denticles ................................. Argyropelecus aculeatus

6b. Lower jaw without prominent canine teeth; post-abdominal spines of similar size, directed anteroventrally; SC photophore scales without denticles ................................................................................................ Argyropelecus sladeni

7a. Dorsal blade consisting of a single spine, anterior margin serrated; BR 3; I 5; PO ventral to orbit, externally indistinct and directed towards mouth ......................................................................................................... ( Sternoptyx )... 8

7b. Dorsal blade small, consisting of two spines, anterior margin smooth; BR 6; I 6; PO anterior to eye, externally distinct and directed towards eye ................................................................................................................... Polyipnus sp.

8a. SAN slightly elevated, closer to anteroventral margin of AN series than to trunk midline ....................................... 9

8b. SAN distinctly elevated to the mid-distance between anteroventral margin of AN and trunk midline or higher ......... ................................................................................................................................................ Sternoptyx pseudobscura

9a. Body height equal to body length; vertebrae 30–32; dorsal-fin rays 11–12 ...................... Sternoptyx pseudodiaphana

9b. Body height much larger than body length; vertebrae 27–29; dorsal-fin rays 9–11 ..................... Sternoptyx diaphana

10a. Anal fin continuous, rays evenly spaced .................................................................................................................... 11

10b.Anal fin interrupted by the AC photophores ............................................................................................................... 13

11a. AC photophores divided into two or three groups, each with 5 or more photophores, none elevated; SO photophores absent ............................................................................................................................. Valenciennellus tripunctulatus

11b. First AC photophore isolated and elevated, followed by two groups of AC photophores; SO photophores present ... .......................................................................................................................................................... ( Maurolicus )... 12

12a. Vertebrae 33–34; gill rakers 25–29, usually 27–29; AC photophores 24–26, usually 25–26; head 27–29% SL .......... .................................................................................................................................................... Maurolicus stehmanni

12b.Vertebrae 32–33; gill rakers 21–26, usually 22–24; AC photophores 22–26, usually 23–24; head 29.5–33% SL ....... ..................................................................................................................................................... Maurolicus weitzmani

13a. VAV and anterior group of several AC photophores forming a continuous serial group of 22–27 organs; dorsal-fin rays 11–14; dorsal-fin origin anterior to anal-fin origin; gill rakers 24–30 (6–8+2+16–20) ...... Argyripnus atlanticus

13b.VAV and 1 or 2 anteriormost AC photophores forming a continuous group of 7–8 organs; dorsal-fin rays 8-9; dorsalfin origin posterior to anal-fin origin; gill rakers 18–21 ...................................................... Sonoda megalophthalma *