A New Species of Acanthurus from the Caroline Islands, 
with Notes on the Systematics of Other Indo-Pacific Surgeonfishes 1 
John E. Randall 
Since the publication of several articles on 
the systematics of surgeonfishes by the author 
(see References), specimens of an undescribed 
species of Acanthurus from the Caroline Islands 
have been obtained as well as information of 
value for various other acanthurids. The op- 
portunity to acquire most of these data was 
provided by a fellowship from Yale University 
and the Bernice P. Bishop Museum for ichthyo- 
logical research in French Oceania. The spec- 
imens of the new Acanthurus were loaned by 
Robert R. Rofen of the George Vanderbilt 
Foundation, Stanford University. For methods 
of counting and measuring see Randall ( 195 6b: 
165). 
Acanthurus chronixis, n. sp. 
Fig. 1 
HOLOTYPE: Stanford Natural History Mu- 
seum No. 52104; Teawataman Ship Pass, south 
side of Kapingamarangi Atoll, Caroline Islands 
(1° 02' 09" N., 154° 45' 04" E.), 1 mi. from 
shore at a depth not greater than 20 ft. over a 
coral, sand bottom; spear; R. Rofen and Kap- 
ingan fishermen; July 13, 1954. One female 
specimen, 211 mm. in standard length and 278 
mm. in total length. 
DESCRIPTION: Dorsal rays VIII, 26; anal rays 
III, 24; pectoral rays 17 (uppermost a short 
bony splint); pelvic rays I, 5; principal caudal 
rays 16; scale rows from gill opening to end of 
caudal spine approximately 150 (not in even 
rows and difficult to count); anterior gill rakers 
22; posterior gill rakers 27; upper teeth 22, with 
7 or 8 denticulations; lower teeth 22, with 6 
or 7 denticulations. 
Depth of body 2.05, head length 3.46, snout 
length, 4.58, length of pectoral fin 3.51, length 
of pelvic fin 4.69, snout to origin of dorsal fin 
1 Contribution No. 268 from The Marine Labora- 
tory, University of Miami. Manuscript received Octo- 
ber 30, 1958. 
2.28, snout to anus 2.34, length of dorsal 
fin base 1.54, length of anal fin base 2.11- — all 
in standard length. Greatest diameter of eye 
4.30, width of body 2.18, width of interorbital 
space 3.08, postorbital length of head 5.92, least 
depth of caudal peduncle 2.56, length of caudal 
peduncle 3.06, length of caudal peduncle spine 
4.06, anus to origin of anal fin 5.08, length of 
pelvic spine 2.04, length of first dorsal spine 
4.92, length of second dorsal spine 2.76, length 
of third dorsal spine 2.44, length of eighth 
dorsal spine 1.92, length of first dorsal ray 1.75, 
length of first anal spine 16.5, length of second 
anal spine 3.18, length of third anal spine 2.30, 
length of first anal ray 2.00, caudal concavity 
1.9, width of mouth 4.26 — all in head length. 
Length of longest upper tooth 3.1 mm.; length 
of longest lower tooth 2.8 mm. Snout produced. 
Stomach large, round, and thick-walled. 
Color in alcohol dark brown; an indistinct 
darker brown spot anterior and adjacent to up- 
per end of gill opening, and a second spot, 
elliptical in shape and more distinct, posterior 
to upper end of gill opening; opercular mem- 
brane darker brown than rest of body; a very 
dark brown band at extreme base of dorsal fin. 
Life colors unknown. 
POSSIBLE JUVENILES: Two small surgeonfish, 
one juvenile, 46.9 mm. in standard length and 
61.2 mm. in total length, and one postacronurus, 
34.5 mm. in standard length and 45.4 mm. in 
total length, were collected from the reef flat 
west of the northern end of Falarik Islet, Ifaluk 
Atoll, Caroline Islands (7° 15' 33" N., 144° 
26' 10" F.) , about .4 mi. from shore at a depth 
of 6 ft. over a bottom of coral, encrusting algae, 
and sand with the use of rotenone by Ifaluk 
fishermen for R. Rofen on October 30, 1953. 
Figure 2 is a photograph of the two specimens. 
The juvenile has a produced snout, and both 
specimens possess eight dorsal spines. Only three 
known species of Acanthurus have eight dorsal 
267 
