Proceedings of the 7th and 8th Symposia on Collection Building and Natural History Studies in Asia and the Pacific Rim,
edited by Y. Tomida et al., National Science Museum Monographs, (34): 273–277, 2006.

Redescription of the Rare Boxfish, Aracana spilonota, with Comments
on Its Taxonomic Position and a Record of Another Rare Boxfish,
Kentrocapros flavofasciatus, from Southeastern Australia
Keiichi Matsuura
Department of Zoology, National Science Museum, 3–23–1 Hyakunin-cho,Shinjuku-ku, Tokyo 169–0073, Japan(e-mail: matsuura@kahaku.go.jp)

Abstract The rare boxfish, Aracana spilonota Gilbert, 1905, is redescribed on the basis of examination on the holotype and 11 additional specimens from the vicinity of Laysan Island, Hawaiian Islands. This species is characterized by having 6 ridges on the carapace and hexagonal body shape incross section, a pair of recurved strong spines on the middle portion of the dorsolateral and ventrolateral ridges. The 6 ridges on the carapace and hexagonal body in cross section indicate that A. spilonota should be reassigned to Kentrocapros. Another rare boxfish, Kentrocapros flavofasciatus (Kamohara, 1938) is recorded for the first time from Australia.
Key words:

boxfishes, Aracana spilonota, Kentrocapros, taxonomy, Hawaii.

Introduction
The deepwater boxfishes of the genus Kentrocapros are represented by three species, K. aculeatus (Houttuyn, 1782) in Japan and the East China Sea, K. flavofasciatus (Kamohara, 1938) inJapan, the East and South China seas and New Caledonia, and K. rosapinto (Smith, 1949) in thewestern Indian Ocean and the southeastern Atlantic (Kamohara, 1938; Smith, 1949; Anonymous,1962; Matsuura & Yamakawa, 1982; Collette & Parin, 1991; Matsuura & Tyler, 1997; Fricke,1999; Armesto et al., 2003; Ikeda, 2003). The rare deepwater boxfish, Aracana spilonota Gilbert,
1905, has been known only from the two type specimens collected by the R/V Albatross from thevicinity of Laysan Island, Hawaiian Islands, at depths of 59 to 163 fathoms (106 to 293 m). During the course of a revisional study on aracanine boxfishes, 11 additional specimens of this rare
boxfish were found in the fish collection of the Bishop Museum in Honolulu. Examination of theholotype and 11 additional specimens indicated that this species should be transferred from Aracana to Kentrocapros. Another rare boxfish, Kentrocapros flavofasciatus (Kamohara, 1938), hasrecently been found in the fish collection of the Australian Museum; it has been known only fromthe Pacific coast of Japan, the East and South China seas, and New Caledonia (Matsuura &Yamakawa, 1982; Matsuura & Tyler, 1997; Ikeda, 2003). Herein, a detailed redescription of Aracana spilonota is provided with comments on its taxonomic position and K. flavofasciatus is reported for the first time from Australia.

274K. Matsuura

Methods
Measurements were made in accordance with the manner of Hubbs & Lagler (1958) except
for the following: head length, the distance from the tip of the snout to the upper end of the gill
opening; body depth, the vertical measurement from the ventral edge of the ventrolateral ridge tothe dorsalmost portion of the carapace at the level of the pectoral-fin base; body width, the distance between the left and right dorsolateral ridges at the level of the pectoral-fin base; gill opening length, the distance between the dorsal and ventral edges of the gill opening; postorbital
length, the distance from the upper end of the gill opening to the nearest point to the orbit; eyediameter, the greatest width of the orbit, not the eye itself; interorbital width, the least bony interorbital width, measured at the anterior edges of the orbits; caudal peduncle length, the distancefrom the posterior edge of the structural base of the last anal ray to the mid-caudal-fin base; caudal-fin length, the distance from the mid-caudal-fin base to the tip of the longest ray; tail length,
the distance from the posterior edge of the lateral ridge of the carapace to the mid-caudal-finbase; tail depth, the vertical distance between the posterior edges of the structural bases of thelast dorsal and anal rays.
Fin ray counts were taken as the total number of elements, regardless of whether the rays arebranched or unbranched. Numbers in parentheses following counts show number of individuals
with that specific count. Values with an asterisk refer to the count obtained for the holotype.
The following institutional abbreviations are used: AMS, Australian Museum, Sydney;
BPBM, Bishop Museum, Honolulu; USNM, National Museum of Natural History, Washington,D.C.
Kentrocapros spilonotus (Gilbert, 1905)(Fig. 1)
Aracana spilonota Gilbert, 1905: 626, fig. 242.

Materials examined. USNM 51630 (holotype), 73.1 mm SL, Albatross station 3939, near
Laysan Island, collected by the R/V Albatross, 59–163 fms (106 to 293 m), 16 May 1902; BPBM
23838 (11 specimens), 57.4–106.0 mm SL, Hawaiian Islands, Molokai, Penguin Bank, 21°10N,157°25W, 177–188 m depth, collected by shrimp trawl Townsend Cromwell cruise 35, station 33,
7 April 1968.
Description. Dorsal-fin rays 9 (1), 10* (8), 11 (3); anal-fin rays 9* (5), 10 (6), 12 (1); pectoral-fin rays 12* (12); caudal-fin rays 11 (12). Body covered with rigid carapace except for caudal peduncle, pectoral, dorsal, and anal-fin bases, and around anus. Carapace with 6 ridges,
namely dorsolateral, lateral, and ventrolateral ridges: dorsolateral ridges start dorsal to the eyes
and extending posteriorly to the level of the dorsal-fin origin; lateral ridges originate in the regionof the posterior edge of each pectoral fin and extend posteriorly to carapace; ventrolateral ridges
beginning below the pectoral-fin bases and running posteriorly to the terminus of the carapace. A
pair of compressed, strong spines on the middle of the dorsolateral ridges, and a corresponding
but smaller pair of spines in the ventrolateral ridges just ventral to the spines on the dorsolateralridges, these 4 spines slightly curving posteriorly; series of low processes along ventrolateralridges posterior to the strong spines.
Most plates on dorsal and lateral sides of carapace hexagonal and sutured firmly to one another; each plate with a central bony tubercle from which 6 (typically) low crests radiate out toabout the middle of each straight edge of the hexagonal plate. Plates on snout and ventral surface

Redescription of the Rare Boxfish, Aracana spilonota

Fig. 1.

275

Kentrocapros spilonotus, holotype, USNM 51630, 73.1 mm SL. Top: lateral view; bottom: dorsal view.

of carapace variously shaped and articulating with one another. Many small and closely articulated plates covering the anterior region of caudal peduncle; isolated groups of small plates extending posteriorly on caudal peduncle to caudal-fin base.
Dorsal surface of carapace slightly convex; interorbital space strongly concave; dorsal profile
of snout almost straight. Lateral sides of carapace between dorsolateral and lateral ridges slightly
concave, and below lateral ridges rather flat or slightly concave. Ventral side of carapace almost
flat.
Mouth small, terminal; lips fleshy and plicate. Eight incisiform or bluntly pointed teeth in asingle row on each jaw. Two nostrils close together, just anterior to eyes. Eyes large, situated posterodorsally on head. Gill opening small, slightly oblique, ventral to posterior half of eye. Dorsal
and anal fins oppositely positioned, slightly rounded. Pectoral fins slightly rounded; the upper 2

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K. Matsuura

rays unbranched; the uppermost ray very short and lowermost ray unbranched. Caudal fin slightlyrounded; the uppermost and lowermost rays unbranched.
Proportional measurements: head length 26.3–35.2% SL, snout length 21.0–26.8% SL, eyediameter 11.6–15.9% SL, interorbital width 10.8–13.6% SL, postorbital length 7.3–10.1% SL,gill opening length 3.6–7.3% SL, snout to dorsal fin 57.4–76.3% SL, snout to anal fin
56.7–76.3% SL, body depth 29.9–41.1% SL, body width 19.3–22.4% SL, dorsal-fin height
13.4–20.4% SL, anal-fin height 12.2–17.3% SL, length of dorsal-fin base 7.7–9.5% SL, length ofanal-fin base 6.6–9.0% SL, pectoral-fin length 15.7–23.2% SL, caudal-fin length 19.3–27.0% SL,
caudal peduncle depth 7.1–9.8% SL, caudal peduncle length 17.3–22.8% SL, tail length
17.7–25.6% SL, and tail depth 18.4–22.7% SL.
Color of specimens in alcohol: body brown with many round dark spots, slightly smaller thanpupil, on dorsal surface of carapace. All fins pale.
Remarks. Gilbert (1905) classified his new boxfish, spilonota, in the genus Aracana which
was a catch-all genus for boxfishes in the early 1900s. However, the true Aracana is represented
by two Australian species, Aracana aurita Shaw, 1798 and A. ornata Gray, 1838, both confinedto the southern waters of Australia. The genus Aracana is characterized by having a relatively
compressed body, rather pentagonal in cross section with a well-developed ventral ridge that
forms a keel on the midline extending from ventral to the eye to the origin of anal fin; a posterolaterally directed spine over each eye; a laterally directed spine on the midlateral side about thelevel of eye, 2 spines each on the dorsolateral and ventrolateral ridges. Conversely, the genus
Kentrocapros is characterized by having a carapace with 6 ridges, hexagonal in cross section andlacking a keel on the ventral surface of the carapace. The characters of Aracana spilonota clearly
indicate that this species should be reassigned to Kentrocapros. As in other species of Kentrocapros, K. spilonotus has been collected from deep waters at depths from 106 m to 293 m.
Kentrocapros flavofasciatus (Kamohara, 1938)
Materials examined. AMS I.29310-001 (1 specimen), New South Wales, off Moruya,
35°46S, 150°34E–35°44S, 150°36E, 155–160 m depth, collected by FRV Kapala, 16 February 1989; AMS I.29734-012 (1 specimen), 122.0 mm SL, Queensland, NE of Coolangatta,28°02S, 153°53E–28°05S, 153°52E, collected by FRV Kapala, 229 m depth, 16 August 1978;
AMS I.31338-001 (3 specimens), 77.5–112.0 mm SL, New South Wales, off Sawtell, 30°22S,153°24E–30°24S, 153°23E, 137–150 m depth, collected by FRV Kapala, 5 September 1990;
AMS I.32119-004 (1 specimen), 126.7 mm SL, New South Wales, Yamba-Iluka, 28°24S,
153°46E–29°21S, 153°47E, 153–175 m depth, collected by FRV Kapala, 22 May 1991; AMS
I.32136-001 (1 specimen), 92.9 mm SL, New South Wales, off Sydney, 33°33S,151°54E–33°31S, 151°56E, 162–165 m depth, collected FRV Kapala, 1 March 1991; AMS
I.32146-001 (1 specimen), 87.3 mm SL, New South Wales, off New Castle, 33°00S,152°12E–32°59S, 152°11E, 133–135 m depth, collected by FRV Kapala, 4 April 1990.
Description. Because Matsuura & Yamakawa (1982) provided the detailed description of K.
flavofasciatus and the Australian specimens do not show significant differences from the previous specimens reported by Matsuura & Yamakawa (1982) and Matsuura & Tyler (1997), the description of this species is not repeated here except for counts and proportional measurements
below.
Dorsal-fin rays 11 (10 in one specimen), anal-fin rays 10, pectoral-fin rays 12 (13 in onespecimen), caudal-fin rays 11.

Redescription of the Rare Boxfish, Aracana spilonota

277

Proportional measurements: head length 28.4–36.7% SL, snout length 23.0–28.8% SL, eyediameter 12.9–17.9% SL, interorbital width 13.9–16.8% SL, postorbital length 7.2–10.1% SL,gill opening length 8.0–11.6% SL, snout to dorsal fin 72.3–82.9% SL, snout to anal fin 71.6–
80.5% SL, body depth 41.6–54.8% SL, body width 24.1–35.2% SL, dorsal-fin height 17.1–
22.7% SL, anal-fin height 15.8–21.3% SL, length of dorsal-fin base 10.1–13.1% SL, length ofanal-fin base 8.6–11.5% SL, pectoral-fin length 18.6–26.9% SL, caudal-fin length 20.1–28.7%
SL, caudal peduncle depth 8.2–11.1% SL, caudal peduncle length 19.1–25.8% SL, tail length
17.0–24.6% SL, tail depth 24.3–30.3% SL.
Remarks. Kentrocapros flavofasciatus has been recorded from the Pacific coast of southern
Japan, the East and South China seas, and New Caledonia in depths of 80–360 m. Matsuura &Tyler (1997) suggested that this species is antitropical in distribution, and the Australian specimens provide a support to their statements.
Acknowledgments
I thank the following persons for loan of the specimens: Mark McGrouther (AMS), John E.
Randall and Arnold Suzumoto (BMBM), and Susan Jewett (USNM). My thanks go to Edward O.
Murdy for his critical comments to the manuscript.
References
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