Chimaera willwatchi, Kemper, 2017

Kemper, Jenny M., 2017, New species of Chimaera (Chondrichthyes: Holocephali: Chimaeriformes: Chimaeridae) from the Southwestern Indian Ocean, Zootaxa 4312 (1), pp. 1-37 : 7-18

Chimaera willwatchi , sp. nov.

Seafarer’s Ghost Shark

( Figs. 6–13 ; Tables 1–2)

Holotype. CAS 242336, 834 + mm TL, 492mm BDL, mature male, Southwestern Indian Ocean , Southwest Indian Ocean Ridge, 33o55’S, 55o16’E, bottom trawl between 850 m – 1075 m, collected by P.J. Clerkin, 24 May 2014.

Paratype. — 9 male, 9 female specimens—CAS 242337, mature male, 823+ mm TL, 456 mm BDL, Southwestern Indian Ocean , Southwest Indian Ocean Ridge, 33o56’S, 55o17’E, midwater trawl between 1008 m – 1190, collected by P.J. Clerkin, 28 April 2014; CAS 242339 , immature male, 843+ mm TL, 466 mm BDL, Southwestern Indian Ocean, Southwest Indian Ocean Ridge, 35o08’S, 55o17’E, bottom trawl between 89 m – 1240 m, collected by P.J. Clerkin, 30 April 2014; CAS 242354 , mature male, 694+ mm TL, 369 mm BDL, Southwestern Indian Ocean , Walters Shoal, 29o51’S, 46o03’E, bottom trawl between 1003 m – 1200 m, collected by P.J. Clerkin, 31 April 2014; USNM 440273 , immature male, 667+ mm TL, 461 mm BDL, Southwestern Indian Ocean , Southwest Indian Ocean Ridge, 35o43’S, 53o43’E, bottom trawl between 860 m – 1110 m, collected by P.J. Clerkin, 23 April 2014; MCZ 171972 , mature male, 782+ mm TL, 490 mm BDL, Southwestern Indian Ocean , Southwest Indian Ocean Ridge, 38o24’S, 48o22’E, bottom trawl between 680 m – 970 m, collected by P.J. Clerkin, 18 March 2012; SIO 16-67 , mature male, 739+ mm TL, 403 mm BDL, Southwestern Indian Ocean , Southwest Indian Ocean Ridge, 35o08’S, 53o42’E, bottom trawl between 825 m – 1180 m, collected by P.J. Clerkin, 17 March 2014; CAS 242338 , mature female, 913+ mm TL, 587 mm BDL, Southwestern Indian Ocean , Southwest Indian Ocean Ridge, 35o08’S, 53o42’E, bottom trawl between 874 m – 1118 m, collected by P.J. Clerkin, 26 March 2014; CAS 242337 , female, 804+ mm TL, 525 mm BDL, Southwestern Indian Ocean , Southwest Indian Ocean Ridge, 33o56’S, 55o17’E, midwater trawl between 1008 m – 1190 m, collected by P. J. Clerkin, 28 April 2014; CAS 242343 , female, 770+ mm TL, 455 mm BDL, Southwestern Indian Ocean , Southwest Indian Ocean Ridge, 39o02’S, 46o33’E, bottom trawl between 777 m – 1178 m, collected by P. J. Clerkin, 17 March 2012; CAS 242367 , female, 920+ mm TL, 522 mm BDL, Southwestern Indian Ocean , Walters Shoal, 34o44’S, 43o44’E, bottom trawl between 1090 m – 1180 m, collected by P. J. Clerkin, 4 April 2014; USNM 440274 , mature female, 948+ mm TL, 604 mm BDL, Southwestern Indian Ocean Ridge , Southwest Indian Ridge, 35o08’S, 53o42’E, bottom trawl between 89 m – 1240 m, collected by P.J. Clerkin, 30 April 2014; SAIAB 203575 , mature female, 826+ mm TL, 576 mm BDL, Southwestern Indian Ocean , Southwest Indian Ocean Ridge, 35o09’S, 53o43’E, bottom trawl between 880 m – 1200 m, collected by P.J. Clerkin, 23 April 2014; SIO 16-68 , mature female, 821+ mm TL, 519 mm BDL, Southwestern Indian Ocean , Southwest Indian Ocean Ridge, 35o08’S, 53o42’E, bottom trawl between 89 m – 1240 m, collected by P.J. Clerkin, 30 April 2014; MB-F035527, immature male, 661+ mm TL, 397 mm BDL, Southwestern Indian Ocean , Southwest Indian Ocean Ridge, 38°22’ S, 47°35’ E, bottom trawl between 700 m – 960 m, collected by B. Walkins, 17 Januaray 2000; MB-F035739, female, 845+ mm TL, 478 mm BDL, Southwestern Indian Ocean , Prince Edward Islands, 39° 50' S, 45° 47' E, trawl between 700 m – 982 m, collected by B. Walkins, 3 May 2001; MB-F035739, mature male, 546+ mm TL, 519 mm BDL, Southwestern Indian Ocean , Prince Edward Islands, 39° 50' S, 45° 47' E, trawl between 700 m – 982 m, collected by B. Walkins, 3 May 2001; MB-F035814, female, 872+ mm TL, 545 mm BDL, Southwestern Indian Ocean , Prince Edward Islands, 39° 26' S, 41° 20' E, trawl between 700 m – 890 m, collected by B. Walkins, 6 May 2001; MB-F035815, immature male, 730+ mm TL, 399 mm BDL, Southwestern Indian Ocean , Prince Edward Islands, 39° 26' S, 41° 19' E, trawl between 700 m – 888 m, collected by B. Walkins, 5 May 2001.

Non-type. — 9 male, 29 female specimens—CAS 242355, 242340, 242342, 242344, 242345, 242346, 242347, 242348, 242349, 242350, 242351, 242352, 242353¸ 242356, 242357, 242358. Males ranged from 479+ to 810+ mm TL, 450 to 152 mm BDL, Southwestern Indian Ocean, 29o51’S to 39o32’S, 44o03’E to 53o42’E, bottom and midwater trawl between 715 m – 1328 m, collected by P.J. Clerkin from 6 March to 3 April 2012 and 23 April to 31 May 2014, and R. Downie between 23 March to 2 April 2014. Females ranged from 290+ to 971+ mm TL, 118 to 645 mm BDL, Southwestern Indian Ocean , 29o51’S to 39o02’S, 44o03’E to 55o16’E, bottom and midwater trawl between 752 m – 1340 m, collected by P.J. Clerkin from 5 March to 13 April 2012 and 18 April to 31 May 2014, and R. Downie between 23 March to 2 April 2014.

Diagnosis. Chimaera willwatchi , sp. nov. is a large species at maturity (971 mm TL, 645 mm BDL) distinguished from all other chimaeroids by the following combination of characters: head blocky, large followed by stocky trunk, body height fairly constant from trunk (pectoral fin origin) to abdomen (pelvic fin origin) before tapering rapidly into long tail; large eyes, and well-defined, blocky suborbital ridge; blunt, distinctly squared snout. Paired claspers eXternally trifurcate, forked distal one-third of length, prepelvic tenacula each with 4 large, toothlike denticles tightly spaced along medial edge. Brownish skin with iridescent wash; brown and white marbled marking around snout, mouth, and ventral half of trunk; posterior margin of first dorsal fin very distinctly white, with white distal margins on anterior half of second dorsal fin, and posterior margins of pelvic fins; dorsal spine, eXceeds the apeX of the first dorsal fin and, when depressed, slightly overlaps the origin of the second dorsal fin, large second dorsal fin not obviously undulating; caudal fin very large and paddle-shaped. Structure of the NADH2 gene. Chimaera willwatchi , sp. nov. can be distinguished from its closest congeners, Chimaera lignaria Didier 2002 , Chimaera macrospina Didier et al. 2008 , and Chimaera orientalis Angulo et al. 2014 , by a combination of characters: large dorsal spine eXceeding apeX of first dorsal fin, long, trifurcated claspers, prepelvic tenacula with 4 spines, robust body, large caudal fin, large pelvic fin anterior margin, and coloration.

Description. Morphometric proportions for the holotype, with ranges for large (> 519 mm BDL) paratypes (male and female separate), and ranges of small non-types (<300 mm BDL; male and female combine) are presented in Table 1. The following description proportions include the holotype followed by paratypes of large specimens with seXes combined in parentheses. Additional descriptive information of small specimens highlighting ontogenetic differences is also provided.

A large-bodied species reaching up to 519 mm BDL in males and 645 mm BDL in females. Head huge, blocky with prominent subocular ridges, head height 26.6% (23̄26.7%) BDL, length about one-fifth (20.6%) precaudal length; snout short, blunt, length about one-half head length; nostrils and mouth below ventral contour of snout; prenarial length 4.0% (3.0̄7.7%) BDL. Trunk slightly compressed, body depth similar to head height, maXimum depth occurs mid trunk, height 30.3% (22.7̄30.7%) BDL, gradually tapering to pelvic girdle, abdomen height 26.8% (18.4̄24.9%) BDL, tapering rapidly to relatively thin tail, 16.6% (12̄24.5%) BDL, and continuing to a caudal peduncle height 3.2% (2.4̄3.0%) BDL. Tail long, making up about one-half (49.5%) precaudal length, relative to trunk length (34.3% of the precaudal length) and head length (22.0% precaudal length). Eyes large, rounded, length about one-third head length, 8.5% (7.6¯9.2%) BDL, height about one-fourth head length, 6.5% (5.1¯7.0%) BDL; preorbital length 28% head length. Interdorsal space short to moderately long, 3.3% (4.6̄10.1%) BDL. Pectoralpelvic space 34.9% (30.0% ̄36.2%) BDL, 1.2–1.4 times head length, and shorter than pelvic-caudal space. Pelviccaudal space 52.3% (49.3–54.5%) BDL, about 1.7–2.2 times head length, and shorter than snout-vent length 67.1% (58.2–67.1%) BDL, 2.2–2.5 times head length. Skin somewhat deciduous, smooth without denticles.

Pectoral fins large, broad, width 22.1% (19.6̄23.2%) BDL, anterior margin 36.8% (33.2̄40.2%) BDL, relatively straight, gradually rounding towards distal tip, posterior margin straight, inner margin rounded; when depressed posteriorly against body, pectoral fin slightly overlaps origin of pelvic fins; pectoral fin base off-round, somewhat angular in shape. Pelvic fins large, very broad, width 16.0% (11.4̄16.7%) BDL, tear-shaped, anterior margin 25.0% (22.9̄26.8%) BDL, about two-thirds (66%) size of pectoral fin, distal two-thirds of anterior margin conveX, inner and posterior margins rounded with fleshy base.

First dorsal fin of moderate height, 20.3% (16.2̄19.1%) BDL, triangular in shape, posterior margin slightly falcate, becomes strongly concave towards insertion into web-like interdorsal ridge and confluent to second dorsal fin. First dorsal fin proceeded by thick, fairly straight spine with slight posterior curve distally, eXtending past the apeX of first dorsal fin, and eXtending to or slightly overlapping second dorsal fin origin when depressed against the body, overlap 7.9% (0.7¯6.4%) BDL; spine anterior edge keeled, strongly trenchant, and marked with a dark brown line; two columns of serrations present on the distal one-third to one-half of the posterolateral edges of spine in mature individuals and entire length in smaller, immature specimens. Second dorsal fin about one-third height of first dorsal, elongated, base 74.8% (70.1̄77.5%) BDL, without any distinct undulation mid-fin, anterior height 6.6% (3.8̄7.2%) BDL slightly greater than middle height 5.9% (3.7̄6.6%) BDL, and posterior height 5.5% (4.1¯6.6%) BDL; fin inserts abruptly, rounding into a small lobe attached to caudal fin by a fleshy web; second dorsal fin somewhat feathery in appearance, easily splitting along radials. Caudal fin very large, paddle-shaped, height approXimately equal in upper and lower margins, dorsal caudal height 4.1% (2.6̄3.7%) BDL, and ventral caudal height 4.1% (3.2̄4.4%) BDL, weakly raked from dorsal origin, tapers into a filament, often damaged in larger specimens; origin of caudal ventral margin is slightly anterior to origin of dorsal margin, connected to a small tab-like anal fin, which is proceeded by a fleshy ridge, dorsal caudal margin 26.6% (25.1̄33.2%) BDL, and ventral caudal margin 36.0% (39.2̄57.3%) BDL.

Holotype Paratype Paratype Nontype

n = 1 n = 9 n = 9 n = 38

Adult Male Male Female (9 Males, 29 Females)

Min MaX Min MaX Min MaX

Body length 492 mm 403 mm 519 mm 519 mm 604 mm 118 mm 285 mm Measurement %BDL %BDL %BDL %BDL

Total Length 158.9 138.8 183.4 142.5 172.6 172.8 219.4 Pre-caudal length 122.8 120.8 126.1 119.6 123.2 120 129.6 Snout to Vent length 67.1 58.2 67.1 59.0 63.9 61.9 71.2 Tail length 57.3 57.3 64.5 60.8 62.6 57.9 61.8 Trunk length 43.1 36.4 42.8 37.4 44.4 40 51.7 Head length 27.0 23.6 28.5 23.0 28.9 22.3 29.3 Pre-first dorsal fin length 30.3 27.9 31.1 27.9 31.3 23.8 36.9 Pre-second dorsal fin length 46.3 46.9 51.8 45.9 53.4 50.5 59.2 Pre-pectoral fin length 29.1 24.0 35.2 24.7 34.7 29.8 33.4 Pre-pelVic fin length 70.9 60.6 69.1 62.4 70.0 64.3 73.0 Pre-orbital length 12.7 11.8 14.0 12.3 13.1 11.2 15.5 Pre-orbital distance 12.9 12.5 14.4 13.0 13.6 12.3 16.1 Pre-narial length 4.0 4.9 7.7 3.0 6.3 4.5 8.3 Pre-narial distance 11.1 9.1 11.8 7.7 10.7 9.3 12.2 Pre-oral length 6.2 6.5 9.6 4.7 8.0 5.4 8.7 Pre-oral distance 14.9 11.5 16.4 11.8 12.9 12.3 14.4 Snout length 12.7 9.2 11.7 7.9 11.1 10.8 12.3 Eye Length 8.5 7.7 9.2 7.6 8.7 10.5 11.7 Eye Height 6.5 5.8 7.0 5.1 6.2 6.2 9.2 First dorsal to pectoral 18.1 17.3 24.2 17.5 28.5 17.5 25.5 First dorsal to pelVic 44.7 37.3 50.8 41.3 45.0 38.9 45.8 Second dorsal to pectoral 29.2 27.1 38.5 26.4 44.6 33.9 39.7 Second dorsal to pelVic 28.3 19.8 28.5 22.8 27.1 20.6 28.5 Snout Width at base 2.3 2.5 3.5 2.0 3.9 1.9 5.2 Snout anterior Width 7.7 6.9 8.6 6.7 7.9 5.8 9.6 Head Width at suborbital ridge 15.8 14.7 16.9 13.9 15.4 12 16

Trunk Width 10.0 12.3 15.0 9.0 15.8 11.6 16.2 Abdominal Width 10.8 8.5 11.2 8.6 12.3 7.5 9.9 Tail Width 8.5 7.2 10.2 6.3 9 4.3 6.6 Cauldal peduncle Width 2.3 1.6 2.2 1.6 2.0 1.7 2.0 Snout height at base 8.1 6.9 9.5 6.8 8.2 6.9 10.5 Head height 26.6 23.0 26.7 23.0 28.5 22.5 27.3 Trunk height 30.3 22.7 30.7 25.6 28.4 24.1 31.6 MaX Trunk height 30.8 23.3 31.1 26.6 31.8 21.1 29.4 Abdomen height 26.8 18.4 24.9 21.1 25.1 18.9 21.9 Tail height 16.6 12.0 24.5 13.1 16.4 12 16.3 Caudal peduncle height 3.2 2.5 3.0 2.4 2.8 2.9 3.7

......continued on the next page Holotype Paratype Paratype Nontype

n = 1 n = 9 n = 9 n = 38

Adult Male Male Female (9 Males, 29 Females)

Min MaX Min MaX Min MaX Frontal tenaculum well developed on mature males, located medially on head, anterior and slightly dorsal to eyes; club-like, thick stalk length greater than one-half eye length, slightly curved, increasing in width distally, terminating in a bulbous tip. Bulb bearing spine-like denticles located on ventral distal surface of tip, varying in size, not in distinct rows, angled posteriorly ( Fig. 8 a). Mature male with eXternally trifurcate, paired pelvic claspers, originating from muscular fin-base, transitioning distally into cartilaginous rod, total length 24.9% (2.7¯24.9%) BDL, forked for at least distal one-third of length; pelvic claspers nearly reaching posterior margin of pelvic fins but not eXceeding distal tip; intermediate branch thin, rod-like, surrounded by broad, soft, fleshy, dilated tip; two lateral branching arms broader, more robust, not widely separated, each with distal fleshy bulbous tip, soft with small denticles giving it a shagreen appearance ( Fig. 8 b). Prepelvic tenacula paired, spatulate, with distal margin of hard structure deeply indented, and concealed within a slit-like pocket on ventral body surface just anterior to pelvic fins; each prepelvic tenacula with 4 large, tooth-like denticles tightly spaced along medial edge; numbered 1 through 4 distally, the second denticle is the largest, 1 and 3 of equal medium size, and 4 being the smallest ( Fig. 8 c). Mature females with fleshy postanal pad, absent in males.

Lateral lines of head open, narrow grooves, those on snout with wide regularly spaced dilations ( Table 2). Preopercular and oral lateral line canals branching varies and is non-descriptive. Lateral line dips strongly just anterior of the spine origin, runs fairly straight along the length of the body and head.

Ontogenetic differences between large and small specimens. Chimaera willwatchi , sp. nov. appears to eXhibit morphogenesis with immature differing from mature specimens in the following characteristics: greater total length (131.3% vs 216.4% BDL), larger eye length (7.0% vs 11.7% BDL) and eye height (5.1% vs 9.2% BDL), thinner snout base width (1.8% vs 7.4% BDL), thinner snout anterior width (5.8% vs 9.6% BDL), thinner head width at suborbital ridges (5.8% vs 9.6% BDL), thinner trunk width (9.0% vs 16.2% BDL), thinner tail width (4.3% vs 8.7% BDL), longer abdomen (28.8% vs 39.3% BDL) and tail lengths (46.8% vs 56.3% BDL), smaller abdomen height (18.4 vs 26.8% BDL) and tail heights (12.0% vs 24.9% BDL), relatively larger pectoral fins (32.2% vs 45.7% BDL), thicker spines, and longer first dorsal fin base (12.9% vs 22.1% BDL). The smallest freeswimming individuals were white with translucent abdomens, but appear to gain pigmentation with growth ( Fig. 10 c).

Dentition. Upper anterior tooth plates (vomerine) moderate, incisor-shaped, with 5 tridors per side, slightly overlapping mandibular tooth plates; posterior upper tooth plates (palatine) moderately large, flat, and ovular in shape; lower tooth plate (mandibular), moderately large, incisor-like, double cusps, transitions posteriorly into concave ridge resulting in 4 and 5 grinding surfaces and 11 tridors per side ( Fig. 8 d).

Coloration. Three distinct color morphotypes were observed and each appears to separate spatially within the SWIO by major submarine geographical features ( Fig. 9 ); each color morph, here designated morphs A, B, and C, and its associated location are provided in the distribution section below.

Morph A specimens prior to preservation are brownish-purple with iridescent-opal, oil-like sheen, brown and white mottling noticeably on snout, around mouth, white labials, and ventral half of trunk; tail brownish-purple, more uniform in color, with light and dark longitudinal striations ( Fig. 10 ). Fins purplish with a slightly grayishbrown and black speckling, dark radials, light basal border; thin dark shading where fin attaches to body; thick white margins very distinct on posterior margin of first dorsal fin and posterior margin of pelvic fins; a thin distinct white marking along anterior edge of second dorsal fin, eXtending up to one-half of fin margin length; white marking present, less distinct along posterior tips of dorsal caudal and ventral caudal fin margins. Lateral lines light in color and bordered by dark shading, running length of head and trunk. After preservation, colors fade, with purple luster and iridescence becoming diminished or lost.

Morph B specimens are a uniform dark brown, with a slightly darker snout and dark lateral striations along tail, but lacking any distinctive markings, mottling, or speckles; fins dark brown-black, lacking white margins ( Fig. 11 ).

Morph C is light beige in body color, speckled, and lighter ventrally, with fins black-purple or light purple in color with dark margins ( Fig. 12 ).

Morph A was collected at all stages of development, whereas morphs B and C only immature specimens were collected. However, similar-sized specimens from each morphotype were compared, and these coloration differences do not appear to be a function of ontogeny. Additionally, color pattern variation correlates strongly by region, and DNA sequence data group based on these locations ( Fig. 13 ).

Etymology. The new species is named in honor of the hard-working fishers onboard the Sealord fishing vessel Will Watch, on which the type specimens were collected. Vernacular: Seafarer’s Ghost Shark.

Size. MaXimum length for females is 645 mm BDL, 971+ mm TL, and for males 519 mm BDL, 834+ mm TL. Smallest free swimming individual 118 mm BDL, 258 mm TL. Females mature at 519 mm BDL, 767 mm TL, and males mature at 369 mm BDL, 638 mm TL.

Distribution. Chimaera willwatchi was encountered on all three main topographic features of the SWIO ( Fig. 9 ): Southwest Indian Ocean Ridge, northern portion of the Madagascar Ridge, and Walters Shoal, 34o30’S – 41o19’E and 39o50’S – 58o15’E; these areas are separated by roughly 600 km and 700 km, respectively. However, each of these areas is represented by a different color morph of the species, which appears to be strongly spatially isolated by sub-region within the SWIO ( Fig. 9 ). Morph A was encountered most frequently, but only along the Southwest Indian Ocean Ridge, Morph B was taken from a single location in the northern part of the Madagascar Ridge, and Morph C was taken from seamounts around Walters Shoal on the southern part of the Madagascar Ridge. There was no overlap in the geographic ranges of each morph type.

Biological notes. Specimens were collected from a wide depth range, 89 m ̄ 1365 m, and encountered in both mid water and bottom trawls. However, there was no trend between depth range and morphotypes.

Comparisons. All comparisons of Chimaera willwatchi were made with specimens> 400 mm BDL, representing mature and larger immature individuals. Chimaeroids eXhibit considerable allometric changes with growth, with smaller immature specimens having proportionally different body dimensions than larger immature and mature specimens ( Kemper et al., 2015). Therefore, removal of smaller immature individuals, those <400 mm BDL, allows for comparisons among similar sized individuals to better discern morphological differences across species; differentiation between species is indicated by either no overlap in a character range or a considerable difference in the minimum or maXimum range of the character ( Kemper et al., 2015).

Chimaera willwatchi is mottled, but lacks strongly defined patterning of spots or reticulations, distinctly separating it from C. monstrosa , C. owstoni and C. panthera that, depending on the species, have distinct reticulations or spotting ( Tanaka, 1905; Didier, 1998; Didier, et al., 2012; Ebert et al., 2013; Kemper et al., 2015). Chimaera willwatchi , although slightly iridescent, lacks any silvery body coloration, usually found in C. argiloba , C. cubana , C. fulva , and C. phantasma ( Jordan and Snyder, 1900; Didier et al., 2002, 2012).

Chimaera willwatchi is a large-bodied species (645 mm BDL), having a blocky head with well-defined suborbital ridges, blunt snout, and strong dorsal spine eXceeding first dorsal apeX. This combination of characters separates C. notafricana (its closest geographic congener) from C. willwatchi by its smaller head length, 21.5% (20.7–23.0%) BDL vs 27.0% (23.0̄28.9%) BDL, shorter spine, 15.9̄22.1% BDL vs 22.9̄27.3% BDL, and shorter eye length, 6.3%–6.5% BDL vs. 8.5% (7.6̄9.2%) BDL. Chimaera obscura is a smaller-bodied species (531 mm BDL), with a smaller head length, 24.5̄25.0% BDL vs 27.0% (23.6̄28.5%) BDL, smaller eye length, 6.1̄7.3% BDL vs 8.5% (7.7̄9.2%) BDL, less developed suborbital ridge, and a greater first dorsal fin height, 23.0̄23.8% vs 20.3 (18.0̄19.1%) BDL that unlike C. willwatchi eXceeds its dorsal spine height. Chimaera opalescens has a larger eye length to head ratio (42.2% head length vs 31.6% head length), shorter dorsal spine, 12.4̄20.2% vs 27.3% (22.9̄24.9%) BDL, spine height not eXceeding first dorsal fin (81.8̄100% first dorsal fin height vs 133.9̄173.1% first dorsal fin height). Chimaera bahamaensis is distinguished by its more pronounced snout, prenarial length 48.0% head length vs 14.8% (10.0̄16.6%) head length, preorbital length 62.0% head length vs 22.9% (16.1̄31.8%) head length. Chimaera carophila is distinguishable by having a smaller head length, 22̄24% BDL vs 27.0% (23.0̄28.9%) BDL, greater eye length to head length ratio (32̄39% head length vs 26.2̄31.6% head length), and shorter spine length, 18̄20% BDL vs 27.3% (22.9̄24.9%) BDL. Chimaera jordani is similar to C. willwatchi , but has a smaller head length, 22.8% BDL vs 27.0% (23.6̄28.5%) BDL, smaller head height 21.6% BDL vs 26.6% (23.0̄26.7%) BDL, and a longer trunk, 52.8% BDL vs 43.1% (36.4̄42.8%) BDL, and smaller eye length, 6.6% BDL vs 8.5% (7.7̄9.2%) BDL.

The species most similar to C. willwatchi are C. lignaria , C. macrospina , and C. orientalis . Chimaera lignaria is most similar to C. willwatchi , having a huge blocky head, robust, stocky body quickly tapering to a long tail, and large fins. However, C. lignaria is known only from the Southwestern Pacific Ocean in the deep waters off New Zealand and Tasmania and is distinguishable from C. willwatchi in having a spine equal to or shorter than first dorsal fin, second dorsal fin rubbery in teXture and not easily split, thin pectoral fins (broad in C. willwatchi ), and rounded pelvic fins not pointed at the leading edge compared to the broad distally pointed pelvic fins of C. willwatchi . Chimaera lignaria is further separated from C. willwatchi by secondary seXual characters, having stout pelvic claspers reaching 17% BDL vs 24.9% BDL, bifurcate vs trifurcate, and prepelvic tenacula with 6 spines vs 4 in C. willwatchi . Chimaera marcospina has a less robust body, generally longer dorsal fin spine, and less broad; caudal fin shorter, ventral caudal margin 27.5̄36% BDL vs 39.2̄57.3% BDL, dorsal caudal fin height 1.7̄3.2% BDL vs 2.6̄4.1% BDL. Chimaera orientalis has a large head and body similar to C. willwatchi , but its fin proportions differ: pectoral fin anterior margin longer, 43.5% (40.0̄41.0%) BDL vs 36.8% (33.7̄40.2%) BDL, pelvic fin anterior margin smaller, 22.2% (20.0¯20.8%) BDL vs 25.0% (22.9¯26.8%) BDL; first dorsal fin similar in height but with shorter base, 10.3̄12.5% BDL vs 17.6% (14.2̄17.9%) BDL, a longer second dorsal fin base, 80.2% (79.2¯81.3%) BDL vs 74.8% (73.2¯77.5%) BDL; interdorsal fin space longer, 10.2% (8.1¯9.7%) BDL vs 3.3% (4.6¯7.2%) BDL; claspers bifurcate, comparatively smaller, 17.5¯17.7% BDL vs 20.4¯24.9% BDL, and with smaller frontal tenaculum, 4.7̄4.6% BDL vs 5.6̄5.7% BDL.

Chimaera willwatchi is the siXth species of chimaera known from the Indian Ocean, but only the second species known to occur in the Western Indian Ocean; this total eXcludes the two new species described below. The only other Chimaera species known to occur in the Western Indian Ocean is C. notafricana , which just barely ranges into the Southwestern Indian Ocean, to Algoa Bay, Eastern Cape Province, South Africa; this species is most common in the Southeastern Atlantic off the west coast of South Africa and Namibia ( Kemper et al., 2010a; Ebert, 2014, 2015). All the other four species, C. argiloba , C. fulva , C. lignaria , and C. macrospina , are only known from the Eastern Indian Ocean and Southwestern Pacific Ocean (Ebert, 2014).

In addition to its morphometric and meristic distinction, C. willwatchi is the only Chimaera species with the unique combination of iridescent sheen when fresh, distinct mottling around mouth, and ventral trunk, very conspicuous white marking on posterior margin of first dorsal fin, anterior edge of second dorsal fin, and posterior margin of pelvic fins. Mottling and white margins are only found in certain geographic populations, and while they are useful to positively identify the species, their absence cannot be relied upon to discount a specimen as C. willwatchi , and should be used in combination with morphometric measurements.

Figures

FIGURE 6. Full body lateral VieW of Chimaera willwatchi, sp. nov., holotype CAS 242336, mature male 834 mm TL, 492 mm BDL, a) Photograph, b) Illustration.

FIGURE 7. Illustration of Chimaera willwatchi, sp. nov., lateral lines of head shoWing: infraorbital to angular canal (IOA), junction of the oral-infraorbital canal to junction of the oral and angular canal, preopercular to main trunk (OTM), preopercular canal (POP), and oral canal (O).

FIGURE 8. Chimaera willwatchi, sp. nov., holotype CAS 242336, mature male 834 mm TL, 492 mm BDL illustrations of a) Frontal tenaculum, b) Lateral VieW of pelVic claspers, c) Pre-pelVic tenacula, d) Tooth plates, and e) Skeletonized skull.

FIGURE 9. Map of study area denoting Where Chimaera willwatchi, sp. nov., specimens Were collected, With subpopulations represented by circles (morph A), star (morph B), and triangles (morph C).

FIGURE 10. Chimaera willwatchi, sp. nov., morph A a) Holotype CAS 242336, mature male 834 mm TL, 492 mm BDL, b) Paratype, immature male, 620 mm TL, 323 mm TL, c) Paratype, neWly hatched female, CAS 242351, 290 mm TL, 117.58 mm BDL.

FIGURE 11. Chimaera willwatchi, sp. nov., morph B a) Non-type CAS, immature male, 694 mm TL, 369 mm BDL, b) Nontype CAS 242354, immature female, 477 mm TL, 252 mm BDL.

FIGURE 12. Chimaera willwatchi, sp. nov., morph C a) Non-type CAS 242358, immature female, 975 mm TL, 542 mm BDL, b) Non-type CAS 242342, immature female, 620 mm TL, 323 mm BDL,

FIGURE 13. MaXimum likelihood tree topology based on a general-time reVersible (GTR) substitution model + gamma distribution for Chimaera willwatchi, sp. nov., Chimaera didierae, sp. nov., Chimaera buccanigella, sp. nov., and comparartiVe species based on aligned NADH 2 DNA sequences. GenBank accession numbers folloW species (see AppendiX 2). Bootstrap support Values of main clades shoWn on tree. Specimens indicated in bold are designated holotypes.