Chaceon linsi, S, M A R C O S Tava R E & Pinheiro, Allysson P., 2011

S, M A R C O S Tava R E & Pinheiro, Allysson P., 2011, A new species of Chaceon Manning & Holthuis, 1989, from the southwestern Atlantic, with a key to the western Atlantic species (Crustacea, Decapoda, Geryonidae), Zootaxa 3086, pp. 57-68 : 58-66

Chaceon linsi n. sp.

( Fig. 1 A, 2A, 3A–C, 4A, D, F)

Chaceon fenneri – Oliveira et al. 1999: 50; Cunha et al. 1999: 531; Sankarankutty et al. 2001: 649; Carvalho et al. 2009: 572; [not Chaceon fenneri ( Manning & Holthuis, 1984) ]

Type material. Brazil: Ceará, 01°45.231'S – 38°15.444'W, J. Coltro coll., 600 m: male holotype cl 136 mm, cw 149 mm ( MZUSP 22287); 1.5°S –4°S to 34°W–42°W: 1 female paratype ( MZUSP 13767). Ceará, Canopus Bank, 120 miles off Fortaleza, J. Coltro col., 400 m: 1 female paratype ( MZUSP 16851); 500 m: 1 male paratype ( MZUSP 16852); 2 males paratypes ( MZUSP 18883). Rio Grande do Norte, 03°39'S – 37°47'W, FV Leiteisteinur, Norte Pesca leg., trap, sand-mud, 529–709 m: 1 male paratype ( MZUSP 21620); 1 male paratype ( MZUSP 21622). Northeastern Brazil, RV Natureza, 1.5°S –04°S to 34.0°W – 42.0° W, 1997: 1 male and 1 female paratypes ( USNM 309757).

Type locality. Brazil, Ceará, 01°45.231'S – 38°15.444'W, 600 m.

Comparative material. Chaceon eldorado Manning & Holthuis, 1989 . Colombia: Oregon, “station” 4912, 12 °06’N– 72°55’W, 31.v.1964, 640– 914 m: 1 male paratype ( USNM 205980). Venezuela: Oregon, “station” 4413, 11 °52’N– 69°25’W, 03.viii. 1963, 640 m: male holotype ( USNM 205982); “station” 2777, 11 °36’N– 62°46’W, H. R. Bullis coll., 19.iv. 1960, 971 m: 2 males paratypes ( USNM 205983); station 11307, 12 °55’N– 70°16’W, 26.xi. 1970, 621 m: 1 female paratype ( USNM 205981). Guadeloupe, Basse Terre, FV Polka, P. Gervain coll., 300–600 m, A. Crosnier det.: 1 female ( MNHN –IU–2011–5565). Trinidad and Tobago: Oregon, “station” 5028, 11 °30’N– 60°46’W, shrimp trawl, 22.ix.1964, 365– 438 m: 1 male ( USNM 1128468). French Guiana: Oregon II, “station” 10616, 07 °37’N– 3°32’W, 13.v. 1969, 723 m: 1 male paratype ( USNM 205984).

Chaceon fenneri ( Manning & Holthuis 1984) . United States: Bermuda: J. P. Ingham coll., 1985, R. B. Manning and L. B. Holthuis det.: 8 males, 8 females and 2 ovigerous females (USNM 228315). Florida Keys: Carysfort, Albatross, “station” 2642, 25 °20’30”N– 79°58’00”N 09.iv. 1886, 396 m: 1 male and 1 female paratypes (USNM 11363). Tortugas I., “station” 68–32, N. L. Schmitt coll. 01.viii.1932, 360+ m: 1 male paratype (USNM 71004); south of Tortugas I., “station” 30–32, N. L. Schmitt coll. 02.vii.1932, 285– 246 m: 2 female paratype (USNM 71003). South of Key West: Gerda , “station” 289, trawl, 24°11’N – 81°36’W to 24°15’N – 81°20’W, 03.iv.1964, 594– 604 m: 1 female paratype (USNM 151084). South of Dry Tortugas Light, Anton Dohrn, A. A. Boyden coll. 6.vi.1939: 384–433 m: 1 female paratype (USNM 78363). South of Dry Tortugas, W. L. Schmitt coll., 31.vii.1930, 402– 433 m: 2 female paratypes (USNM 71112). 18 miles Due south from No. 2 Red Buoy, station 18, otter trawl, W. Schmitt coll., 3.vii.1931, 375– 404 m: 1 male and 1 ovigerous female paratypes (USNM 68205). W. Fernandina, RV Albatross, “station” 2669, 31 °09’N– 79°33’30”W, 05.v. 1986, 643 m: 1 male paratype (USNM 14373); “station” 2666, 30 °47’30”N– 79°49’W, 05.v. 1986, 493 m: male holotype (USNM 14376). Gulf of Mexico: Oregon II, “station” 168, 28 °04’N– 85°27’W, taken by shrimp trawl, 9.ix. 1968, 502 m, R. B. Manning and L. B. Holthuis det.: 1 male (USNM 1128467); [Oregon II?] 27°00.77'N – 84°54.96'W, R. Erdman coll., R. B. Manning leg., 402 m, R. B. Manning and L. B. Holthuis det.: 1 female (MZUSP 19993).

Chaceon inghami ( Manning & Holthuis 1986) . Bermuda, offshore: J. P. Ingham coll., 1985, trap: 1 male paratype (USNM 228197); summer 1984, trap, 2560 m: male holotype (USNM 228197), 1 male paratype (USNM 205333). J. P. Ingham coll., 25.ii.1985, trap, 914–1005 m: 1 male paratype (USNM 228196).

Chaceon notialis Manning & Holthuis, 1989 . Brazil: Rio de Janeiro?, C. M. Cunha coll.: 1 male (MZUSP 18084). São Paulo, RV Prof. W. Besnard, Projeto Integrado, “station” 5362, dredge, 24°48’S – 44°29’W, 500 m: 1 male and 1 female (MZUSP 12824). Paraná, REVIZEE, Projeto Armadilhas and Pargueiros, cruise 2, “station” 1, 25 °44,618'S– 46°15,938'W, 144 m: 2 females (MZUSP 18887). Paraná, UNESP São Vicente, trap 3, 26°17’656S’– 45o38’939’W, 800 m: 1 male (MZUSP 19933); Paraná?, CLP, III Cruzeiro, “station” 15, 500 m: 1 male (MZUSP 20527). Santa Catarina, PADCT, “station” 6634, otter trawl, 27°18.900'– 47°05.200'W, 310m: 1 female (MZUSP 12842). RV Soloncy Moura, “station” 1866, 27°27'457''S–47°06'186''W, 550 m: 1 male (MZUSP 15726); “station” 1827, 27°17'810''S–47°02'409''W, 450 m: 1 male (MZUSP 15727); “station” 1895, 27 °26.628'S– 47°09.799'W, 350 m: 1 female (MZUSP 15729); “station” 1841, 27 °11.124'S– 46°52.300'W, 450 m: 1 male (MZUSP 15730); “station” 1824, 27 °26.888'S– 47°08.083'W, 450 m: 1 male (MZUSP 15731). Argentina: RV Cruz del Sur, 37°45’S – 54°55’W, Inst. Biol. Mar. coll., 17–18.v.1973, 280– 320 m: 1 ovigerous female paratype (USNM 205702); 38°55’S – 55°35’W, Inst. Biol. Mar. coll., 16.iv.1973, 170 meters: male holotype (USNM 205702). Argentine Basin, “station” 237, Woods Hole Oceanographic Institution coll., 11.iii.1971, 993– 1011 m, R. B. Manning and L. B. Holthuis det.: 1 male (USNM 252416); “station” 236, 11.iii.1971, 497– 518 m, R. B. Manning and L. B. Holthuis det.: 1 male (USNM 252415).

Chaceon quinquedens ( Smith 1879) : United States: Massachusetts, off Cape Ann, Speedwell, “station” 35, 19.viii. 1877, 292 m: S. Smith det. 1 male and 1 female syntypes (USNM 40000). Off New Jersey, CABP expedition, “station” J1, 38 °44’12”N– 73°00’54”W, Virginia Institute of Marine Sciences, coll. 20.vi.1976, trawl, 315– 400 m: 1 male and 1 female (USNM 185424); 38°45'N – 73°01'W, Virginia Institute of Marine Science leg., 25.viii. 1976, 400 m: 1 female (MZUSP 16086). Gulf of Mexico: RV Gyre, “station” S42, 28 °14’56”N– 86°24’39”W, 10.vi.2000, 770– 800 m, M. K. Wicksten det.: 3 males and 1 female (USNM 1022349); “station” S36, 28 °55’59”N– 87°38’42”W, 12.vi.2000, 1715– 1852 m, M. K. Wicksten det.: 1 male and 2 females (USNM 1022066). Off Florida, RV Citation, “station” E2D, 28°07’38”N – 85°51’36”W, LGL Ecological Research Associates for BLM/ MMS coll., 16.v.1985, 624– 631 m, M. K. Wicksten det.: 2 males (USNM 1024941). Bahamas: Tongue of the Ocean, Columbus Iselin, “station” 46, 24.ii.1973, otter trawl, 1234 m, F.M. Bayer det.: 1 male (USNM 151085).

Chaceon ramosae Manning, Tavares & Albuquerque, 1989 : Brazil: Rio de Janeiro, RV Marion Dufresne, cruise TAAF MD55, “station” 5, CP 11, 21 °35'S– 40°05'W, 10.v.1987, 248– 262 m: 1 male paratype (MZUSP 9363). São Paulo, RV Albatross, “station” 2763, 24 °17’S– 42°48.30’W, beam trawl, 30.xii. 1987, 1302 m, R. B. Manning, M. Tavares and E. F. Albuquerque det.: 1 male paratype (USNM 22072). São Paulo, PADCT, “station” 6628, 24 °30.300'S– 44°13.000'W, 455 m: 1 male and 1 female (MZUSP 18886); “station” 6628, 24 °30.300'S– 44°13.000'W, 455 m: 5 males (MZUSP 18884). Projeto Integrado, RV Prof. W. Besnard, “station” 5362, dredge, 24°48’S –44°29’, 500 m: 1 male (MZUSP 23891). Paraná, Programa REVIZEE, Projeto Armadilhas and Pargueiros, cruise 2, “station” 1 #456, 25 °44.618'S– 46°15.938'W, 144 m: 2 males (MZUSP 18882). Paraná, UNESP São Vicente, 26°17.656’S – 45°38.939’W, trap 3, 800 m: 1 male (MZUSP 19934). Paraná, UNESP São Vicente coll., CLP, cruise III, “station” 15, 500 m: 1 female (MZUSP 20526). Santa Catarina, RV Soloncy Moura “station” 1858, 27°26'628''S–47°09'799''W, 350 m: 1 male (MZUSP 15728); station 6637, 27 °00.500'S– 46°36.800'W, 323 m: 2 females (MZUSP 18885); PADCT, “station” 6636, RV Prof. W. Besnard, 27°27’S – 46°52’W, 811m: 6 males (MZUSP 18473). Santa Catarina, MOBIO/CEPSUL/ICMBio coll., RV Soloncy Moura, 15.viii.2009, trap 3, 27 °46.24'S– 27°46.53'S to 47°00.99'W – 47°00.68'W, 530–568 m: 7 males and 8 females (CEPSUL 172); 26.x.2009, 27°36.376'S – 47°08.971'W, 468 m: 2 males (CEPSUL 174); 28.x.2009, 29°05.959'S – 47°45.597'W, 560 m: 3 males (CEPSUL 173); 28.ii.2010, 26°50.933'S – 46°10.483'W, 620m: 2 males (CEPSUL 175); 12.iii.2010, 29°03.952'S – 47°45.365'W, 600 m: 2 males (CEPSUL 168); 12.iii.2010, 28°30.58'S – 46°48.669'W, 970 m: 4 males (CEPSUL 169); 14.iii.2010, 27°41.242'S – 46°53.359'W, 772 m: 2 males (CEPSUL 171). Rio Grande do Sul, Projeto Talude, RV Atlântico Sul: 1 male (MZUSP 8992). Rio Grande do Sul FV Kimpo Maru, “station” 2966, 34 °33,400'S– 51°50,090'W, 652 m: 1 male left P5 regenerated (MZUSP 15732).

Chaceon sanctaehelenae Manning & Holthuis, 1989 : St. Helena., southeast coast, Sandy Bay, 15o58’S – 0 5o 43’W, F.N. Martin coll., 08.x.1968, crayfish trap: male holotype (USNM 125510).

Description. Large size of carapace (cw 164 mm, cl 141 mm), dorsal surface transversely and longitudinally convex. Gastric region strongly swollen, granular; granules large, flat. Hepatic regions gently convex, finely granular. Four clusters of very low granules aligned in convex curve opposite to last anterolateral tooth, 2 adjacent clusters near carapace axis concave, showing as scars; posterobranchial region markedly swollen, densely granular. Metagastric, cardiac regions laterally delimited by deep, distinctly rugose grooves. Suborbital, sub-branchial and subhepatic regions with scattered, very low granules; pterygostomial region with scattered granules, punctate. Median frontal and lateral frontal teeth of about same size; median frontal extending slightly forward of lateral frontal teeth; distance between two median frontal teeth about the same as that between one median frontal tooth and its adjacent lateral frontal tooth; frontal teeth prominent, triangular. Supraorbital margin entire, submedian and adjacent fissures showing as scars; fissures not obvious from dorsal view. Infraorbital margin lined with acute granules, inner edge with strong, acutely triangular tooth. Anterolateral margin strongly convex; outer orbital tooth strong, acutely triangular; second anterolateral tooth low, broadly triangular; third small, acutely triangular; fourth obsolete to indistinct (small and large specimens, respectively); last strong, sharp to acutely triangular (small and large specimens, respectively). Posterolateral margin slightly convex, granular. Posterior margin of carapace lined with strong granules, median margin straight. Eye cornea well developed, dark brown. Antenna occupying part of orbital hiatus, movable, not fused with carapace; article 1 mesially swollen; article 2+3 rectangular, flattened; article 3 cylindrical, longer than preceding; article 5 cylindrical, short; flagellum long, about 1.5 articles 1‒5 length. Mxp3 merus squarish, external and internal angles rounded. Ischium subrectangular, with deep longitudinal sulcus. Mesial margins of merus and ischium heavily setose. Suture between ischium and basis incomplete, interrupted medially. Exopod stout, reaching almost to external angle of merus; flagellum well developed, as long as width of merus and palp together. Chelipeds equal in size and form. Outer surfaces mottled, granular. Merus with strong, sharp, subdistal tooth on dorsal margin, distal tooth absent; ventral margin spineless. Carpus with strong, welldeveloped sharp tooth on distal inner margin, no outer spine; outer surface strongly granular, with uneven ridges arranged in semi-reticulate pattern. Propodus with no distodorsal spine; lateral surface of palm granular, with uneven, low ridges arranged in semi-reticulate pattern; distinct longitudinal granular ridge ending before base of fingers. Fingers slightly shorter than palm, cutting edges with proximal molariform, crushing teeth, followed by well-developed, acutely triangular teeth and denticles. P2‒P5 meri with no distodorsal spine. P2‒P5 dactyli laterally compressed, curved. Distal end of P5 merus extending far beyond tip of last carapace anterolateral tooth. P5 carpus with dorsolongitudinal line of low granules. Maximum length of dorsolongitudinal, corneous ridges of P5 dactylus about 1/4 of maximum length of P5 dactylus. Surface of thoracic sternum smooth, punctate; thoracic sternal sutures 2/3 and 3/4 faint; sutures between sternites 2‒6 incomplete, interrupted medially; sutures from sternite 6 onwards complete; abdomen-locking button on posterior edge of sternite 5. Male abdomen with six somites plus telson; all sutures distinct, but segments 3‒5 not movable; telson broadly triangular, rounded tip. G1 short, very stout, C-shaped; distal part tubular, gradually tapering to tip, strongly curved outwards; series of long setae on submedian part of outer margin; one-third distal area covered with numerous, very small truncate spines. G2 almost as long as G1, very slender, gently curved outwards; distinct distal article about one-quarter total length. Female thoracic sternum wide, sterno-abdominal cavity shallow, formed by sternites 8–4, densely pubescent. Sternal sutures 2 / 3 and 3 / 4 faint; 4 / 5 and 5 / 6 deep, medially interrupted; 6 / 7and 7 / 8 deep, complete. Female abdomen with 6 freely-movable somites plus telson. Somites 1, 2 completely covering thoracic sternum between P5 coxae, thoracic sternite 8 not visible; somite 3 very close to margin of sternite 7, small portion of thoracic sternite 7 visible only laterally. Abdominal somite 6 longest. Telson large, width twice the length, extending from thoracic sternite 5 to sternal sutures 2 / 3. Vulvae small, transversally oval, opening near thoracic sternal suture 5 / 6, completely covered by abdominal somite 6.

Etymology. Named after our colleague and friend Jorge Eduardo Lins de Oliveira (Federal University of Rio Grande do Norte) in recognition of his contributions to oceanography and fishery biology in northeastern Brazil.

Remarks. Chaceon linsi n. sp. has been confused in the past with C. fenneri because of its laterally compressed P2–P5 dactyli (Sankarankutti et al. 2001: 649). However, both species can be easily distinguished in that in Chaceon linsi n. sp. (i) the distal end of the merus of P5 extends far beyond the tip of the last carapace anterolateral tooth, whereas in C. fenneri the distal end of merus of P5 reaches to the tip of the last carapace anterolateral tooth at most ( Fig. 1 A–B); (ii) the male P5 merus height is twice, or slightly more than twice, the maximum length of the dactylus, whereas in C. fenneri P5 merus height is nearly three times the maximum length of the dactylus; (iii) the distance between the median frontal teeth is about the same as the distance between one median frontal tooth and its adjacent lateral frontal tooth, whereas in C. fenneri the median frontal teeth are much closer as the distance between them is distinctly shorter than the distance between one median frontal tooth and its adjacent lateral frontal tooth ( Fig. 2 A–B); (iv) the distance between the outer orbital and third anterolateral teeth is markedly smaller than that between the third and last anterolateral teeth, whereas in C. fenneri the distance between the outer orbital to third and that between the third to last anterolateral teeth varies from slightly smaller to slightly larger (equal in some specimens) ( Fig. 2 A–B); and (v) the distal end of G1 reaches to the thoracic sternal suture 6/7, whereas C. fenneri has a distinctly longer G1, reaching to sternite 6, sometimes almost to the sternal suture 5/6.

Chaceon linsi n. sp. differs from C. atopus and C. inghami in having the anterolateral teeth of carapace small or obsolete (versus strong and sharp anterolateral teeth in C. atopus and C. inghami ); P2–P5 meri with no spine distodorsally (versus one distodorsal distinct spine in C. atopus and C. inghami ); P1 merus with one subdistodorsal distinct spine only (versus one distodorsal and one subdistodorsal distinct spines in C. atopus and C. atopus ); P1 propodus with no distodorsal spine (versus one distinct distodorsal spine in C. atopus and C. inghami ); P1 carpus with no outer spine (versus one strong distal outer spine in C. atopus and C. inghami ); P5 carpus with dorsolongitudinal line of low granules (versus dorsolongitudinal line of distinct spinules in C. atopus and C. inghami ).

Chaceon linsi n. sp. differs from C. sanctaehelenae in that the distal end of merus of P5 extends far beyond the tip of the last anterolateral tooth (versus extending only a little beyond the tip of the last anterolateral tooth in C. sanctaehelenae ); the frontal teeth are prominent, triangular (versus low, lobe-like in C. sanctaehelenae ); the maximum length of the dorsolongitudinal corneous ridges of the P5 dactylus is about 1/4 of the maximum length of P5 dactylus (versus slightly longer than 1/6 of the maximum length of P5 dactylus in C. sanctaehelenae ).

Chaceon linsi n. sp. differs from C. eldorado , C. notialis , C. quinquedens , and C. ramosae in having the dactyli of P2–P5 laterally compressed ( Fig. 3 A–C), whereas those species have the dactyli of P2–P5 dorsoventrally depressed ( Fig. 3 G–I).

Manning & Holthuis (1989: table 1) summarized the main characteristics of the species of Chaceon known then. Color, shape of the P5 dactylus, presence and size of the distal spine on the P5 merus, and presence and size of the anterolateral teeth of the carapace were considered critical to differentiate among species. However, apart from color ( C. eldorado and C. notialis are red, whereas C. ramosae is tan), C. eldorado , C. notialis , and C. ramosae share: (i) dorsoventrally depressed P5 dactylus; (ii) distal spine on the P5 merus reduced to a tubercle; and (iii) small or reduced anterolateral teeth of carapace. Therefore, these three species cannot be separated by the above characters alone.

Chaceon eldorado differs from C. notialis ( Figs. 1 D, 5D) by: (i) P5 merus distal end extending far beyond the tip of the last (fifth) carapace anterolateral tooth in C. eldorado , whereas in C. notialis the P5 merus reaches at most to the tip of the last anterolateral tooth; and (ii) P5 merus maximum length as long as distance between the base last anterolateral tooth and the inner supraorbital tooth, whereas in C. notialis the P5 merus maximum length much shorter than the distance between the base last anterolateral tooth and the inner supraorbital tooth, reaching only to the frontal tooth of the opposite side.

Large and small specimens of Chaceon eldorado and C. ramosae differ from each other in that the P5 merus maximum length is distinctly more than twice as long as the P5 dactylus of C. eldorado , whereas in C. ramosae the P5 merus maximum length is twice as long as the P5 dactylus. Large specimens of C. eldorado and C. ramosae further differ from each other by: (i) overall the body distinctly more finely granulated, especially on the chela, branchial, and intestinal regions, versus coarsely granulated in C. ramosae ; (ii) second anterolateral tooth obsolete, versus low, broadly triangular in C. ramosae ; (iii) the G2 distinctly shorter not reaching to the thoracic sternal suture 6/7, versus overreaching that suture in C. ramosae ; (iv) mxp3 merus with rather prominent external angle, versus external angle rounded in C. ramosae .

Chaceon notialis can be easily distinguished from C. ramosae by: (i) the length of the P5 merus reaching to the tip of the last anterolateral tooth at most, whereas in C. ramosae the P5 merus distal end extends far beyond the tip of the last anterolateral tooth ( Fig. 1 C–D); (ii) the P5 merus maximum length is much less than twice as long as the P5 dactylus, whereas in C. ramosae the P5 merus maximum length is twice as long as the P5 dactylus; (iii) mxp3 merus with prominent external angle, whereas in C. ramosae the mxp3 external angle is rounded.

Fisheries. Five of the eight western Atlantic species of Chaceon are commercially important: C. fenneri ( National Oceanic and Atmospheric Administration 1995; Tavares 2002), C. linsi n. sp., C. notialis , C. quinquedens ( Tallack 2007; Wahle et al. 2008), and C. ramosae .

Both Chaceon notialis and C. ramosae have been fished in the southwestern Atlantic since the 1980s either as Geryon quinquedens or under their current names (Lima & Branco 1991; Perez et al. 2003; Pezzuto et al. 2006; Valentini & Pezzuto 2006). Brazilian landings of C. notialis and C. ramosae between 2000 and 2006 were of about 6 and 4 tons, respectively ( Perez et al. 2009). These figures are to be used with extremely caution, however, because until now distinguishing between these two species was difficult.

Between 2003 and 2007 Chaceon linsi n. sp. was fished in northeastern Brazil either as C. fenneri or Chaceon sp. ( Brasil. Ministério do Meio Ambiente 2006; Carvalho et al. 2009; Lessa 2006), where captures fluctuated between about 23 (2003) and 3 tons (2007).

Figures

FIGURE 1. Relative size of P 5 merus, dorsal view. A, Chaceon linsi n. sp., male holotype cl 136 mm, cw 149 mm (MZUSP 22287). B, Chaceon fenneri (Manning & Holthuis, 1984), male paratype cl 130 mm, cw 161 mm (USNM 71004). C, Chaceon ramosae Manning, Tavares & Albuquerque, 1999, male paratype cl 141 mm, cw 157 mm (MZUSP 9363). D, Chaceon notialis Manning & Holthuis, 1989, male holotype cl 95 mm, cw 104 mm (USNM 205701). In A and C the distal end of the P 5 meri extend far beyond the tip of the last anterolateral tooth of the carapace. Scale bars: A, 30 mm, B ‒ D, 50 mm.

FIGURE 2. Habitus, dorsal view. A, Chaceon linsi n. sp., male holotype cl 136 mm, cw 149 mm (MZUSP 22287). B, Chaceon fenneri (Manning & Holthuis, 1984), male paratype cl 130 mm, cw 161 mm (USNM 71004). Scale bars: A, 30 mm; B, 50 mm.

FIGURE 3. P 5 dactylus. A ‒ C, Chaceon linsi n. sp., male holotype cl 136 mm, cw 149 mm (MZUSP 22287). D ‒ F, Chaceon fenneri (Manning & Holthuis, 1984), male paratype cl 130 mm, cw 161 mm (USNM 71004). G ‒ I, Chaceon quinquedens (Smith, 1879), male cl 105 mm, cw 129 mm (USNM 185424). J ‒ M, Chaceon sanctaehelenae Manning & Holthuis, 1989, male holotype cl 112 mm, cw 134 mm (USNM 125510). A, D, G, J dorsal views; B, E, H, L ventral views; C, F, I, M lateral views. Scale bars: A ‒ C, 30 mm; D ‒ F, 20 mm; G ‒ M, 10 mm.