Garthambrus darthvaderi, Mclay, Colin L., 2009

Mclay, Colin L., 2009, Revision of the crab genus Garthambrus Ng, 1996, with the description of two new genera and discussion of the status of Tutankhamen Rathbun, 1925 (Crustacea: Brachyura: Parthenopidae), Zootaxa 2122, pp. 1-50 : 13-16

publication ID	https://doi.org/ 10.5281/zenodo.188125
DOI	https://doi.org/10.5281/zenodo.6212864
persistent identifier	https://treatment.plazi.org/id/9C5487F9-FF8E-FF9E-24D8-417CFEB5FB5A
treatment provided by	Plazi
scientific name	Garthambrus darthvaderi
status	sp. nov.

Treatment

Garthambrus darthvaderi View in CoL sp. nov.

( Figs 6 View FIGURE 6 A, B, 11)

Type material. HOLOTYPE: male 19.9 x 14.0 mm ( MNHN), New Caledonia, BIOCAL, stn DW44, 22°47’S, 167°14’E, 440–450 m, 30 Aug 1985.

PARATYPES: 1 female 13.0 x 9.5 mm, 1 ovig. female 20.5 x 14.5 mm ( MNHN), New Caledonia, MUSORSTOM IV, stn 162, 18º35.0’S, 163º10.3’E, 525 m, 16 Sep 1985; 1 female 17.8 x 13.4 mm ( MNHN), BATHUS 3, stn DW838, 23º01’S, 166º56’E, 400–407 m, 30 Nov 1993; 1 female 19.2 x 13.4 mm ( MNHN), BATHUS 4, stn DW925, 18º54.55’S, 163º23.75’E, 370–405 m, 7 Aug 1994.

Material examined. New Caledonia. VAUBAN: Dredge 16 (ex DR2)”, 22º46’S, 167º12’E, 390–400 m, 10 Apr 1978: 1 female 14.1 x 9.9 mm ( MNHN).

MUSORTSOM IV: stn 230, 22º52.50’S, 167º11.80’E, 390–420 m, 30 Sep 1985: 1 female 20.4 x 14.1 mm ( MNHN).

BIOCAL: Stn DW77, 22º15’S, 167º15’E, 440 m, 5 Sep 1985: 1 female 18.0 x 13.0 mm (MNHN).

MUSORSTOM IV: stn 162, 18º35.0’S, 163º10.3’E, 525 m, 16 Sep 1985: 1 ovig. female 20.5 x 14.5 mm (MNHN).

SMIB 1: stn DW10, 22º54’S, 167º12’E, 410 m, 6 Feb 1986: 1 male 18.9 x 13.4 mm (MNHN).

SMIB 2: stn DW14, 22º53’S, 167º13’E, 405–444 m, 18 Sep 1986: 1 male 19.4 x 13.6 mm, 1 female 18.1 x 12.7 mm (MNHN).

MUSORSTOM V: stn 301, 22º06.9’S, 159º24.6’E, 487–610 m, 21 Oct 1986: 1 female 15.2 x 10.8 mm (MNHN); Stn 379, 19º53.20’S, 158º39.50’E, 370–400 m, 20 Oct 1986: 1 male 18.9 x 13.1 mm (MNHN).

BERYX 11: stn DW11, 24º44’S, 168º10’E, 320–350 m, 16 Nov 1992: 1 male 19.0 x 13.1 mm (MNHN); Stn CP21, 24º44’S, 168º07’E, 430–450 m, 17 Oct 1992: 1 male 18.9 x 13.3 mm, 1 female 19.0 x 13.4 mm (MNHN).

SMIB 8: stn DW187, 23º17.7’S, 168º05.6’E, 390–540 m, 31 Jan 1993: 1 male 18.2 x 13.2 mm (MNHN); Stn DW189, 23º17.6’S, 168º05,5’E, 400–402 m, 31 Jan 1993: 1 male 15.4 x 10.8 mm, 1 female 18.9 x 13.3 mm (MNHN); Stn DW191, 22º57.5’S, 168º19.2’E, 564–580 m, 1 Feb 1993: 1 female 8.8 x 6.6 mm (MNHN).

BATHUS 2: stn DW719, 22º47.57’S, 167º14.58’E, 444–455 m, 11 May 1993: 1 male 18.8 x 12.5 mm (MNHN); Stn DW729, 22º52.42’S, 167º11.90’E, 400 m, 12 May 1993: 1 female 19.4 x 12.0 mm (MNHN); Stn DW730, 23º02.56’S, 166º58.30’E, 397–400 m, 12 May 1993: 2 males 6.5 x 5.2, 8.0 x 5.9 mm, 2 females 9.0 x 6.5, 17.4 x 12.8 mm (MNHN); Stn CP736, 23º03.38’S, 166º58.96’E, 452–464 m, 13 May 1993: 1 female 15.8 x 10.9 mm (MNHN); Stn CP737, 23º03.42’S, 166º59.97’E, 350–400 m, 13 May 1993: 2 males 9.3 x 7.0, 15.6 x 10.7 mm (MNHN).

BATHUS 3: stn DW830, 23º20’S, 168º01’E, 361–365 m, 29 Nov 1993: 2 females 13.0 x 9.4, 18.3 x 12.9 mm (MNHN); Stn DW838, 23º01’S, 166º50’E, 400–407 m, 30 Nov 1993: 1 female 18.2 x 13.0 mm; Stn CP847, 23º03’S, 166º58’E, 405–411 m, 1 Dec 1993: 2 females 14.2 x 10.3, 16.9 x 12.1 mm (MNHN).

HALIPRO 1: stn CP877, 23º3’S, 166º59’E, 464–480 m, 31 Mar 1994: 1 male 6.4 x 4.8 mm (MNHN).

BATHUS 4: stn DW927, 18º55.48’S, 163º22.11’E, 452– 444 m, 7 Aug 1994: 2 males 13.4 x 9.0, 34.5 x 25.0 mm, 1 female 25.8 x 18.4 mm (MNHN).

HALICAL 1: stn DW04, 18º55’S, 163º24’E, 350–365 m, 28 Nov 1994: 1 female 18.0 x 12.7 mm (MNHN).

Loyalty Islands. MUSORSTOM VI: stn DW391, 20º47.35’S, 167º05.70’E, 390 m, 13 Feb 1989: 1 male 13.0 x 9.2 mm, 1 female 11.5 x 8.4 mm (MNHN); Stn DW406, 20º40.65’S, 167º6.80’E, 373 m, 15 Feb 1989: 1 male 13.0 x 9.2 mm (MNHN); Stn DW411, 20º40.60’S, 167º3.35’E, 424 m, 15 Feb 1989: 2 females 9.8 x 7.2, 19.4 x 13.2 mm (MNHN); Stn DW412, 20º40.60’S, 167º3.25’E, 437 m, 15 Feb 1989: 1 male 10.1 x 7.4 mm (MNHN); Stn DW459, 21º01.39’S, 167º31.47’E, 425 m, 20 Feb 1989: 1 female 19.1 x 13.1 mm (MNHN); Stn CP464, 21º2.30’S, 167º31.60’E, 430 m, 21 Feb 1989: 3 males 9.5 x 7.2–19.3 x 14.1 mm, 6 females 17.3 x 11.9–19.4 x 13.1 mm (MNHN); Stn DW479, 21º13.50’S, 167º54.95’E, 310 m, 22 Feb 1989: 1 female 13.0 x 9.5 mm (MNHN); Stn DW487, 21º23.20’S, 167º46.40’E, 500 m, 23 Feb 1989: 2 males 18.3 x 12.1, 18.3 x 12.5 mm, 2 females 9.2 x 6.9, 14.5 x 10.3 mm (MNHN).

Chesterfield Islands- Bellona Plateau. CHALCAL 1984: stn CP8, 19º43.80’S, 158º35.25’E, 348 m, 19 Jul 1984: 1 male 18.7 x 12.4 mm (MNHN).

Norfolk Ridge. SMIB 5: stn DW98, 23º01.7’S, 168º16.1’E, 335 m, 14 Sep 1989: 1 male 12.4 x 9.1 mm (MNHN).

Description. Carapace sub-pentagonal, wider than long, ratio CW/CL = 1.4, surface smooth except for occasional eroded areas or small pits scattered over surface. Carapace surface without any major projections.

Median rostral tooth short bluntly rounded, horizontal. Lateral rostral teeth scarcely evident. Frontal region with small central concavity. Dorsal orbital margins not elevated, mid-orbital depression only faintly marked. Protogastric region convex, mesogastric with narrow, rounded median ridge that extends posteriorly, continues after small constriction on to metagastric, cardiac, intestinal regions. Hepatic region slopes steeply to hepatic margin which stands out strongly behind orbit. Anterior branchial region with only one broad ridge (corresponding to posterior ridge) that does not quite extend to posterior epibranchial margin. Small low rounded prominence in posterior branchial region close to posterior epibranchial margin. Branchiocardiac groove with 3 small pits on each side, solitary tubercle absent.

Orbital margin smooth, concave to well marked supraorbital suture. Concave suborbital margin ends in sub-acute tooth. Complete hepatic margin prominent, descending almost vertically from beneath postorbital corner; posterior edge bluntly rounded. First anterior epibranchial tooth close to hepatic projection, armed with 11 finely tuberculate teeth, initially distinct, but tending to merge, forming flattened margin near posterior epibranchial corner. Posterior epibranchial margin concave, one large tooth just behind posterior epibranchial corner. Posterior margin marked by broad blunt tubercles on each side with slightly concave margin in between.

Epistome with small central depression widely separated from depressions at each corner. Sub-hepatic region deeply concave with deep open fissure at bottom; fissure running from near base of suborbital tooth to posterior hepatic margin. Strong lamelliform ridge runs parallel to hepatic fissure, interrupted by hepatic notch lying beneath first anterior epibranchial tooth, continuing on sub-branchial area where it disappears. Cheliped-blocking mechanism involves proximal spine on posterior margin of cheliped merus meeting subbranchial spine near cheliped base. Depression on male sternites 3, 4 U-shaped, with larger tubercle at each corner. Sternites 5, 6, 7 with curved tuberculate ridges on anterior epibranchial corners decreasing in size posteriorly, preceded by small concavities. No ridges on mature females, where space is taken up by abdomen. Only sternal suture 6/7 complete in males, females.

Eyes mobile, eyestalks granular, short, diameter same as cornea, at right angles to body axis; margin of orbit incomplete ventrally, orbital fossa deep, formed by lateral, suborbital margins Around 80% of cornea concealed when eye folded away.

Antennal article 1 (urinal article) mobile, wider than long, convex; article 2 (basal article) trapezoidal, convex, fixed to epistome, suborbital margin; articles 3, 4 mobile, longer than wide; flagellum as long as articles 3, 4 combined.

Medial edge of basis-ischium of third maxilliped blade-like, without setae; central longitudinal concavity present. Surface of merus densely granular; distal depressions, separated by ridge marked by one strong tubercle plus several other tubercles. Distolateral corner of endopod merus conceals end of third maxilliped exopod. Carpus, propodus, dactylus of endopod decreasing in size distally, last two articles folded under merus.

Inner margin of cheliped merus armed with 12 sub-acute tubercles of varying size; outer margin with 8 tubercles, last 3 median, curving downward from dorsal to ventral margin. Most distal tubercle largest. Cheliped carpus with one sub-acute tubercle mid-way near upper border. Outer margin of propodus armed with 5 or 6 evenly spaced, blunt tubercles; inner margin with 8 tubercles, increasing in size distally, last 4 curving towards base of dactylus. Dactylus with 3 or 4 obsolete tubercles on upper margin. Teeth on cheliped fingers weakly developed: right cheliped (crusher) gaping, with 2 teeth, left cheliped (cutter) with 3 teeth on opposing margins. Male cheliped length 2.4x CW or 3.3x CL; mature female cheliped length 1.8x CW or 2.5x CL.

Ambulatory legs decrease in length posteriorly. Formula describing arrangement of tubercles on articles of each limb: P2: without tubercles; P3: merus 0/(3+1); P4 merus 0/(3+3); P5 merus 1/(3+2); all other articles without tubercles.

Third abdominal segment lateral areas have prominent tubercle, central area depressed. Segments 4–6 with central ridge, scattered tubercles. Medial hook on segment 6 absent in males, females. Segments 3–5 fused in male, only suture 4/5 evident near margins. Abdominal locking mechanism present in males, immature females, sometimes in mature females, although tubercles on sternite 5, sockets on abdominal segment 6 present. Telson wider than long, tip bluntly rounded in males, females.

Female gonopore circular, situated mid-way on sternite 6, not raised above sternal surface, closed by flexible cover (but non-operculate). G1 reaches anterior margin of sternite 5, narrows quickly to straight section distally, sperm aperture sub-terminal, medial, tip minutely spinose. Spinose tip occupies last 21% of G1. G2 reaches middle of sternite 4, slightly longer than G1, flagellum twisted. Proximal end of flagellum marked by small notch. Ratio of flagellum length/total length of G2 = 0.47. Ratio of length of G2/G1 = 1.28.

Distribution. New Caledonia, Loyalty Is, Chesterfield Plateau and Norfolk Ridge.

Etymology. The species name is derived from the sinister “Star Wars” character, “Darth Vader”, the “helmeted one”, and it alludes to the helmet-like appearance of the front of this species.

Remarks. Garthambrus darthvaderi resembles G. pteromerus but differs mainly in that the hepatic tooth is absent in G. darthvaderi , but present in G. pteromerus ; the carapace surface is more pitted in G. pteromerus . Also G. p t e ro m e r u s has a small concavity immediately behind the orbits that is much shallower G. darthvaderi .