Family No. 256: TETRAGONURIDAE
by R.L. Haedrich
Squaretails
Stompsterte
Body slender and rounded. First dorsal fin of 10-21 short
spines folding into a groove; second dorsal and anal fins
short and similar, with 9-17 rays. Pelvic fins folding into a
sh'allow groove. Caudal peduncle long and thick, square in
cross-section. Mouth peculiar and box-like; premaxilla not
protractile; maxilla covered almost entirely by expanded
preorbital bone; lower jaw shuts within upper. Teeth small,
pointed and curved in upper jaw; large , flattened and knifelike in lower jaw. Opercles fleshy. Scales moderate in size
with heavy keels, adherent, following a geodesic pattern
around body . Modified scales form 2 lateral keels on each
side of peduncle near caudal fin; snout naked; cheek with
scales.
Pelagic, worldwide in warmer waters. Attains 70 cm. Not
food-fishes and may even at times be poisonous, but they
are eaten by tunas and other large predators. Feed on softbodied invertebrates; juveniles commonly associate with
salps. A single genus, revised by Grey (1955).
Genus Tetragonurus Risso, 1810
Three species; all may be expected in our area.
KEY TO SPECIES
la Lateral series of scales to caudal keels 97-114;
vertebrae 52-58; V well behind P base ... ..... .. .... ... ...... ... T. cuvieri
1 b Lateral series of scales to caudal keels 73-95;
vertebrae 40-51; V under or just behind P base ..... ..... ...... .... .... 2
2a D spines 10-11 ; lateral series of scales 73-78;
vertebrae 40- 43 .. .. .. ... .. ... .......... .... ... ... ... .. ... ......... T. pacificus
2b D spines 14-17; lateral series of scales 83-95,
vertebrae 45-51 ......... ...................... .... .. .............. T. at/anticus
256.1 Tetragonurus at/anticus: 21 em (Natal).
256.2 Tetragonurus cuvieri: 15 em (after Grey. 1964).
256: TETRAGONURIDAE (SQUARETAILS)
256.1 Tetragonurus at/anticus
Lowe, 1839
Bigeye squaretail
Grootoog-stompstert
Tetragonurus atlanticus Lowe, 1839: 79 (Madeira); Grey, 1955: 17*;
Haedrich, 1967: 98; Ahlstrom et al. , 1976: 325* .
D XIV-XVII,lO-13; A I,9-12; P 14-18; interorbital distance equal to eye
diameter; snout only slightly longer than eye diameter; D origin over middle of P.
Light brown to almost black. Attains 50 cm. Atlantic,
Pacific and Indian oceans.
256.2 Tetragonurus cuvieri
Risso, 1810
Smalleye squaretail
Kleinoog-stompstert
Tetragonurus cuvieri Risso, 1810: 347 (Mediterranean); Smith, 1953:
521 , No. 844a; 1953: 62*; Grey, 1955: 27*; Haedrich, 1967: 98 *; Ahlstrom
et al., 1976: 329*.
D XV-XXI,1O-17; A I, 10-15; P 14-21; interorbital distance greater than
eye diameter; snout considerably longer than eye diameter; D origin over
or behind tip of P.
Light to dark brown, almost black; young greyish.
Attains 70 cm. May be reasonably abundant offshore.
Natal; also western Mediterranean, eastern Atlantic and
Pacific oceans.
256.3 Tetragonurus pacificus
Abe, 1953
Pacific squaretail
Stille oseaan-stompstert
Tetragonurus pacificus Abe , 1953: 45 , Figs. 5 & 6 (Solomon Ids.); Grey,
1955: 14*; Haedrich, 1967: 98; Ahlstrom et al., 1976: 333* .
D X-XI,1O-12; A I,1O-12; P 15-17. Interorbital distance equal to eye
diameter; snout only slightly longer than eye diameter. D origin over middle of P.
Light grey to brown . Attains 30 cm? A tropical species of
the Pacific and Indian oceans. Unknown from our area, but
to be expected as a stray.
851
by R.L. Haedrich
Squaretails
Stompsterte
Body slender and rounded. First dorsal fin of 10-21 short
spines folding into a groove; second dorsal and anal fins
short and similar, with 9-17 rays. Pelvic fins folding into a
sh'allow groove. Caudal peduncle long and thick, square in
cross-section. Mouth peculiar and box-like; premaxilla not
protractile; maxilla covered almost entirely by expanded
preorbital bone; lower jaw shuts within upper. Teeth small,
pointed and curved in upper jaw; large , flattened and knifelike in lower jaw. Opercles fleshy. Scales moderate in size
with heavy keels, adherent, following a geodesic pattern
around body . Modified scales form 2 lateral keels on each
side of peduncle near caudal fin; snout naked; cheek with
scales.
Pelagic, worldwide in warmer waters. Attains 70 cm. Not
food-fishes and may even at times be poisonous, but they
are eaten by tunas and other large predators. Feed on softbodied invertebrates; juveniles commonly associate with
salps. A single genus, revised by Grey (1955).
Genus Tetragonurus Risso, 1810
Three species; all may be expected in our area.
KEY TO SPECIES
la Lateral series of scales to caudal keels 97-114;
vertebrae 52-58; V well behind P base ... ..... .. .... ... ...... ... T. cuvieri
1 b Lateral series of scales to caudal keels 73-95;
vertebrae 40-51; V under or just behind P base ..... ..... ...... .... .... 2
2a D spines 10-11 ; lateral series of scales 73-78;
vertebrae 40- 43 .. .. .. ... .. ... .......... .... ... ... ... .. ... ......... T. pacificus
2b D spines 14-17; lateral series of scales 83-95,
vertebrae 45-51 ......... ...................... .... .. .............. T. at/anticus
256.1 Tetragonurus at/anticus: 21 em (Natal).
256.2 Tetragonurus cuvieri: 15 em (after Grey. 1964).
256: TETRAGONURIDAE (SQUARETAILS)
256.1 Tetragonurus at/anticus
Lowe, 1839
Bigeye squaretail
Grootoog-stompstert
Tetragonurus atlanticus Lowe, 1839: 79 (Madeira); Grey, 1955: 17*;
Haedrich, 1967: 98; Ahlstrom et al. , 1976: 325* .
D XIV-XVII,lO-13; A I,9-12; P 14-18; interorbital distance equal to eye
diameter; snout only slightly longer than eye diameter; D origin over middle of P.
Light brown to almost black. Attains 50 cm. Atlantic,
Pacific and Indian oceans.
256.2 Tetragonurus cuvieri
Risso, 1810
Smalleye squaretail
Kleinoog-stompstert
Tetragonurus cuvieri Risso, 1810: 347 (Mediterranean); Smith, 1953:
521 , No. 844a; 1953: 62*; Grey, 1955: 27*; Haedrich, 1967: 98 *; Ahlstrom
et al., 1976: 329*.
D XV-XXI,1O-17; A I, 10-15; P 14-21; interorbital distance greater than
eye diameter; snout considerably longer than eye diameter; D origin over
or behind tip of P.
Light to dark brown, almost black; young greyish.
Attains 70 cm. May be reasonably abundant offshore.
Natal; also western Mediterranean, eastern Atlantic and
Pacific oceans.
256.3 Tetragonurus pacificus
Abe, 1953
Pacific squaretail
Stille oseaan-stompstert
Tetragonurus pacificus Abe , 1953: 45 , Figs. 5 & 6 (Solomon Ids.); Grey,
1955: 14*; Haedrich, 1967: 98; Ahlstrom et al., 1976: 333* .
D X-XI,1O-12; A I,1O-12; P 15-17. Interorbital distance equal to eye
diameter; snout only slightly longer than eye diameter. D origin over middle of P.
Light grey to brown . Attains 30 cm? A tropical species of
the Pacific and Indian oceans. Unknown from our area, but
to be expected as a stray.
851