Porstlarval Scombroids from the Central Pacific — Strasburg 
175 
TABLE 1 
Station Data, 'Hugh M. Smith” Cruise 47 
STATION 
NO. 
DATE 
(1958) 
ZONE 
TIME 
LATITUDE 
LONGITUDE 
MAXIMUM 
HAUL DEPTH 
(in m) 
2 
Oct. 9 
2005-2300 
21° 24' N 
158° 23' W 
139 
32 
Oct. 27 
1315-1523 
00° 02' S 
149° 32' W 
85 
49 
Nov. 2 
0843-1027 
02° 09' S 
149° 47' W 
99 
51 
Nov. 2 
2013-2158 
00° 44' S 
149° 46' W 
85 
53 i 
Nov. 3 
0838-1018 
00° 37' N 
149° 58' W 
86 
56 
Nov. 4 
1030-1210 
01° 56' N 
150° 09' W 
98 
58 
Nov. 4 
2013-2153 
02° 56' N 
150° 03' W 
93 
60 
Nov. 5 
0820-1002 
04° 28' N 
150° 29' W 
96 
66 
Nov. 6 
2005-2152 
09° 08' N 
150° 03' W 
96 
68 
Nov. 7 
0820-1007 
10° 40' N 
149° 52' W 
93 
70 
Nov. 7 
2015-2148 
12° 13' N 
149° 56' W 
96 
finlets have not yet differentiated. The fin formu- 
lae are D XXVII, 24 and A 22 as a consequence 
of persistent membranes between the fins and 
presumptive finlets. The anal formula is addi- 
tionally misleading in that spines and rays can- 
not be distinguished. As is apparent from Figure 
2, the spacing between the rays of the future 
finlets is greater than between the rays of the 
soft dorsal and anal fins. Further demarcating 
the finlets is the dusky pigment of their mem- 
branes. Following finlet formation this fish 
would presumably have had fin formulae of D 
XXVII, 14 + 10 and A 12 + 10. 
Other characters of this specimen are 23 pec- 
toral rays, I, 5 pelvic rays, 7 branchiostegal rays, 
and 17 principal caudal rays. All caudal rays, 
except the 3 mesial ones, have their bases cover- 
ing the hypurals, tending to conceal the latter. 
The gill filaments are J -shaped but as yet show 
no tendency to fuse into the adult gill reticulum. 
Tooth size and spacing are irregular, in contrast 
to the homodont adult dentition, with about 28 
teeth on each dentary and 25 on each premaxil- 
lary. The anterior teeth in both jaws are curved 
and fanglike. The anterior margin of the pre- 
opercle bears a short spine at the angle and 
another on the lower limb. The posterior margin 
has two short spines on the upper limb, a long 
spine at the angle, and five irregular spines on 
the lower limb. There are two tiny spines on 
the posterior tip of the pterotic, but these are 
too small to appear in the drawing. The body is 
dusted with tiny melanophores, giving a uni- 
form tan color, except on the dorsal part of the 
snout, which is dark brown. 
An unusual feature of this specimen is a 
conical cartilaginous projection surmounting the 
mandibular symphysis. This projection has been 
noted in the adult, but not commented upon 
(Conrad, 1938:10). A similar structure has 
phylogenetic significance in relating the Gem- 
pylidae and Trichiuridae (Tucker, 1956:123), 
as well as taxonomic importance within the 
Gempylidae (Grey, 1953:138). Because its pres- 
ence in Acanthocybium was thought to indicate 
hitherto unsuspected relationships between the 
Scombridae and the Gempylidae-Trichiuridae, a 
search was made for the structure in other 
scombroids. There is no indication of it in the 
young of any of the tunas ( Auxis , Euthynnus, 
Germo, Katsuwonus, Neothunnus, Parathunnus, 
and Thunnus ) according to W. M. Matsumoto 
(personal communication), but a prominent 
mandibular protuberance was found in juvenile 
Scomberomorus maculatus, 11.5-19.2 mm in 
standard length. Scomberomorus is regarded as 
phylogenetically basal to Acanthocybium (Fraser- 
Brunner, 1950:135), and the presence of this 
jaw projection confirms a close relationship. 
That there is a tie between these genera and the 
Gempylidae-Trichiuridae is further indicated 
by their mutual low-crested crania, elongate 
compressed bodies, and reduced squamation. In 
all scombroids examined, including a 565-mm 
