Descriptions of new Australian chondrichthyans 123 Bythaelurus incanus sp. nov., a new deepwater catshark (Carcharhiniformes: Scyliorhinidae) from northwestern Australia Peter R. Last & John D. Stevens CSIRO Marine & Atmospheric Research, GPO Box 1538, Hobart, Tas 7001, AUSTRALIA ABSTRACT.— Bythaelurus incanus, a new species belonging to a rare genus of deepwater catsharks, is described based on a single specimen collected from the Ashmore Terrace, off northwestern Australia LQDERXWPGHSWK,WFRPSOLHVFORVHO\ZLWKWKHGH¿QLWLRQRI&RPSDJQR¶VUHFHQWO\HOHYDWHGVXEJHQXV of the genus Halaelurus. Bythaelurus incanus differs from most of its congeners in morphometrics and colour, being uniformly plain coloured both dorsally and ventrally rather than spotted and blotched, weakly saddled or paler ventrally, and in denticle and tooth morphologies. Key words. Scyliorhinidae – Bythaelurus incanus – deepwater catshark – new species – Australia PDF contact: [email protected] INTRODUCTION FDXGDO FHQWUDRIWKHFDXGDO¿Q YHUWHEUDH7KHKRORW\SH is deposited in the Australian National Fish Collection, Members of the subgenus Bythaelurus Compagno, Hobart (CSIRO). 1988, were initially assigned to the genus Halaelurus (Compagno, 1984). Compagno (2005) elevated the group to genus level, presumably based on the combination of Bythaelurus incanus sp. nov. FKDUDFWHUVXVHGWRGH¿QHKLVVXEJHQXV+HOLVWHGVHYHQ members of the group: Bythaelurus alcockii (Garman, Figs 1, 2; Table 1 1913), B. canescens (Günther, 1878), B. clevai (Séret, 1987), B. dawsoni (Springer, 1971), B. hispidus (Alcock, HalaelurusVS$/DVW 6WHYHQVSSNH\¿J 1891), B. immaculatus (Chu & Meng in Chu, Meng, Hu ¿JSO&RPSDJQRet al., 2005: p 215, pl. 35. & Li, 1982), B. lutarius (Springer & D’Aubrey, 1972), of which B. alcockii is considered questionable. Compagno Holotype. &6,52 + ± MXYHQLOH PDOH PP et al. (2005) provided short descriptions of these species TL, south of Roti Island, Ashmore Terrace, Western and included two extra undescribed species: a new $XVWUDOLDƍ6ƍ(±P-DQ species from the Galapagos Islands (as B. sp. B) and DQ $XVWUDOLDQ VSHFLHV SUHYLRXVO\ LGHQWL¿HG E\ /DVW DIAGNOSIS.— A Bythaelurus with the following Stevens (1994) as B. sp. A. The new Australian species combination of characters: head short and broad, width is formally named and described below based on a single 13.5% TL, length 19.1% TL; snout short, broadly specimen collected off northwestern Australia. URXQGHGOHQJWKLQKHDGOHQJWKDQWHULRUQDVDOÀDSV triangular; mouth large, width 10.3% TL, length 4.6% 7/ ODELDO IXUURZV VKRUW FRQ¿QHG WR PRXWK FRUQHUV METHODS roof of mouth with small papillae; abdomen elongate, SHFWRUDO±SHOYLF VSDFH WLPHV OHQJWK RI SHFWRUDO¿Q Morphometric methods generally followed a widely anterior margin, 1.7 times interdorsal space; predorsal adopted scheme for elasmobranchs (Compagno, 1984, distance about 42% TL, 10.9 times eye length; anal- 2001), but focused on direct rather than horizontal FDXGDOGLVWDQFH7/¿UVWGRUVDO¿QRULJLQVOLJKWO\ measurements. The holotype was measured in full EHKLQGRULJLQRISHOYLF¿QVHFRQGGRUVDO¿QRULJLQZHOO (Table 1) and meristics were taken from radiographs. EHKLQGDQDO¿QPLGEDVHDQDO¿QEDVHOHQJWKWLPHV Meristics were obtained separately for total, trunk VHFRQG GRUVDO¿Q EDVH OHQJWK VXEHTXDO WR LQWHUGRUVDO (monospondylous), precaudal (monospondylous + VSDFH ÀDQN GHQWLFOHV ZHDNO\ WULFXVSLGDWH FURZQV GLSORVSRQG\ORXVWRRULJLQRIXSSHUOREHRIFDXGDO¿Q DQG very slender, their length more than twice their width; 124 A B Figure 1. Bythaelurus incanus VSQRYMXYHQLOHPDOHKRORW\SH &6,52+±PP7/ $GRUVDOYLHZ% lateral view. teeth minute with mainly 4 small cusps, central pair pair longest, outer medial cusp longer than lateral cusp; ORQJHUWKDQWKRVHDGMDFHQWDERXWURZVLQHDFKMDZ QHDUDQJOHRIMDZFHQWUDOSDLURQO\VOLJKWO\ORQJHUWKDQ ÀDQN GHQWLFOHV XSULJKW ZHDNO\ WULFXVSLGDWH DERXW lateral cusps; cusps with basal grooves. SUHFDXGDO FHQWUD EHIRUH XSSHU FDXGDO¿Q RULJLQ ERG\ uniformly greyish brown. Flank denticles very small, bristly, erect, weakly tricuspidate; well separated, not imbricate, similar in DESCRIPTION.— %RG\ UREXVW ÀDEE\ GHSUHVVHG size; crowns narrow (length more than twice width) with anteriorly, somewhat tadpole shaped; arched above a well-developed median ridge, lateral ridges absent; their SHFWRUDO¿QVEHOO\VOLJKWO\H[SDQGHGWDSHULQJVWURQJO\ apices elongate and narrowly pointed; denticles along EHKLQG ¿UVW GRUVDO ¿Q +HDG VWURQJO\ GHSUHVVHG VKRUW dorsal caudal margin densely packed, smaller than those DQGEURDGOHQJWKZLGWK7/ZLGHVWMXVW DGMDFHQWGHQWLFOHVRQEHOO\EURDGHUGHQVHUVPDOOHUWKDQ forward of 1st gill slit; broadly parabolic in dorsoventral WKRVHRIÀDQNODFNLQJPHGLDQULGJHRQFURZQ view, bluntly pointed in lateral view; lateral angle of VXERUELWDOVKHOIZHOOGH¿QHGVXSUDRUELWDOFUHVWWKLQJLOO )LUVWGRUVDO¿QWDOOVWURQJO\UDNHGSUHFHGHGE\DGHHS VOLWV GRUVRODWHUDO ODVW WZR VOLWV RYHU SHFWRUDO¿Q EDVH groove; anterior margin long, weakly convex; apex slightly closer together than slits 1–3; slits decreasing narrowly rounded; posterior margin short, truncate; free SURJUHVVLYHO\LQOHQJWKIURP¿UVWWR¿IWK6QRXWEURDGO\ rear tip obtusely angular; inner margin long, straight, rounded, length 2.93 in head length. Eye dorsolateral, REOLTXHO\XSULJKWVPDOOHUWKDQVHFRQGGRUVDO¿QRULJLQ slit-like, length 1.67 in snout; suborbital groove well- VOLJKWO\EHKLQGRULJLQRISHOYLF¿QSUH¿UVWGRUVDOOHQJWK developed, slightly longer than eye; orbito-spiracular 7/6HFRQGGRUVDO¿QWDOOVWURQJO\UDNHGSUHFHGHG groove continuous; interorbital width 1.31 times snout E\DGHHSJURRYHWKDWH[WHQGVWR¿UVWGRUVDO¿QDQWHULRU length, 2.23 in head length. Spiracle very small, suboval, margin long, weakly convex; apex narrowly rounded; well separated from eye; dorsolateral on head, length SRVWHULRU PDUJLQ WUXQFDWH PXFK ORQJHU WKDQ LQ ¿UVW LQLQWHURUELWDOZLGWK$QWHULRUQDVDOÀDSH[SDQGHG GRUVDO¿Q IUHHUHDUWLSREWXVHO\DQJXODULQQHUPDUJLQ laterally, triangular, partly overlapping outer lobe but short, straight, obliquely upright; pre-second dorsal not reaching mouth, posterior margin usually entire; OHQJWK7/RULJLQZHOOEHKLQGDQDO¿QPLGEDVH internarial width subequal to length of nasal cavity. LQVHUWLRQ ZHOO EHKLQG IUHH UHDU WLS RI DQDO ¿Q$QDO ¿Q Mouth long and broad, width 2.23 times length; roof of ODUJHUWKDQVHFRQGGRUVDO¿Q EDVHORQJHUEXWKHLJKWRI¿Q mouth and tongue pleated and weakly papillose; labial less); anterior margin long, weakly convex; apex broadly furrows rudimentary; postoral grooves absent. Jaw teeth rounded; posterior margin weakly concave; free rear tip minute, villiform, recurved slightly medially, in oblique narrowly angular; inner margin short, weakly concave; rows; mainly with 4 sharp cusps; near symphysis central DQDO¿Q OHQJWK WLPHV SHOYLF±DQDO VSDFH 3HFWRUDO Descriptions of new Australian chondrichthyans 125 Table 1. Morphometric data for the holotype of Bythaelurus incanus sp. nov. (CSIRO H 1204–02). Measurements expressed as a percentage of total length. Total length (mm) 454 Caudal peduncle width 1.8 Precaudal length 71.8 3HFWRUDO¿QDQWHULRUPDUJLQ 13.0 Pre-second dorsal length 58.8 3HFWRUDO¿QEDVHOHQJWK 5.6 3UH¿UVWGRUVDOOHQJWK 42.4 3HFWRUDO¿QKHLJKW 8.9 Head length 19.1 3HFWRUDO¿QLQQHUPDUJLQ 5.2 Prebranchial length 16.5 3HFWRUDO¿QSRVWHULRUPDUJLQ 8.8 Prespiracular length 12.0 3HOYLF¿QOHQJWK 9.9 Preorbital length (horizontal) 5.1 3HOYLF¿QDQWHULRUPDUJLQ 6.1 Preorbital length (direct) 6.5 3HOYLF¿QEDVHOHQJWK 7.3 Preoral length 5.3 3HOYLF¿QKHLJKW 4.5 Prenarial length 3.6 3HOYLF¿QLQQHUPDUJLQ 3.3 Prepectoral length 20.1 3HOYLF¿QSRVWHULRUPDUJLQ 6.1 Prepelvic length 40.3 )LUVWGRUVDO¿QOHQJWK 8.7 Snout–vent length 43.2 )LUVWGRUVDO¿QDQWHULRUPDUJLQ 8.5 Preanal length 52.6 )LUVWGRUVDO¿QEDVHOHQJWK 5.8 Interdorsal space 10.1 )LUVWGRUVDO¿QKHLJKW 3.3 Dorsal–caudal space 5.5 )LUVWGRUVDO¿QLQQHUPDUJLQ 2.9 Pectoral–pelvic space 17.1 )LUVWGRUVDO¿QSRVWHULRUPDUJLQ 2.5 Pelvic–anal space 5.9 6HFRQGGRUVDO¿QOHQJWK 11.1 Anal–caudal space 6.3 6HFRQGGRUVDO¿QDQWHULRUPDUJLQ 11.2 Eye length 3.9 6HFRQGGRUVDO¿QEDVHOHQJWK 8.4 Eye height 0.4 6HFRQGGRUVDO¿QKHLJKW 4.5 Interorbital width 8.6 6HFRQGGRUVDO¿QLQQHUPDUJLQ 2.3 Nostril width 2.7 6HFRQGGRUVDO¿QSRVWHULRUPDUJLQ 3.7 Internarial space 3.0 $QDO¿QOHQJWK 11.9 $QWHULRUQDVDOÀDSOHQJWK 2.4 $QDO¿QDQWHULRUPDUJLQ 9.1 Spiracle length 0.6 $QDO¿QEDVHOHQJWK 9.7 Eye–spiracle space 1.5 $QDO¿QKHLJKW 3.4 Mouth length 4.6 $QDO¿QLQQHUPDUJLQ 1.9 Mouth width 10.3 $QDO¿QSRVWHULRUPDUJLQ 5.2 Upper labial furrow length 0.5 &DXGDO¿QGRUVDOFDXGDOPDUJLQ 26.6 Lower labial furrow length 0.4 &DXGDO¿QSUHYHQWUDOFDXGDOPDUJLQ 11.9 First gill slit height 1.9 &DXGDO¿QXSSHUSRVWYHQWUDOPDUJLQ 12.9 Fifth gill slit height 1.0 &DXGDO¿QVXEWHUPLQDOPDUJLQ 5.2 Head height 7.0 &DXGDO¿QWHUPLQDOPDUJLQ 4.8 Trunk height 6.6 &DXGDO¿QWHUPLQDOOREH 4.7 Caudal peduncle height 3.4 6HFRQGGRUVDORULJLQDQDO¿QRULJLQ 5.1 Head width 13.5 6HFRQGGRUVDOLQVHUWLRQDQDO¿QLQVHUWLRQ 3.9 Trunk width 11.5 ¿Q ODUJH OREHOLNH DQWHULRU PDUJLQZHDNO\ FRQYH[ LWV not developed, slightly depressed, not reaching beyond length 13.0% TL; apex narrowly rounded; posterior FORDFD&DXGDO¿QODUJHHORQJDWHZLWKDORZGRUVDOOREH margin almost straight; free tip broadly rounded; inner and a weak ventral lobe; terminal lobe well developed, PDUJLQ ZHDNO\ FRQYH[ 3HOYLF ¿Q VPDOO OHQJWK narrow, broadest distally, its posterior margin weakly of TL; anterior margin almost straight, apex broadly concave; origin of dorsal lobe well forward of apex of rounded; posterior margin weakly concave; free rear tip YHQWUDOOREHRULJLQRIYHQWUDOOREHLQGLVWLQFWÀHVK\SDUW narrowly angular; inner margin almost straight. Claspers RIOREHRULJLQDWLQJMXVWSRVWHULRUWRRULJLQRIGRUVDOOREH 126 Figure 2. Ventral view of head