Camatopsis minor, Ng, Peter K. L. & Castro, Peter, 2016

Ng, Peter K. L. & Castro, Peter, 2016, Revision of the family Chasmocarcinidae Serène, 1964 (Crustacea, Brachyura, Goneplacoidea), Zootaxa 4209 (1), pp. 1-182 : 42-44

Camatopsis minor n. sp.

( Figs. 8 G, H; 23F; 39G, H; 69A‒F; 86E)

? Camatopsis rubida — Serène & Soh 1976: 23, fig. 21 [Andaman Sea]. Not Camatopsis rubida Alcock & Anderson, 1899 . Camatopsis rubida Forma B—Tesch 1918: 235 (part) [ Indonesia] (other Forma B specimens = Microtopsis teschi n. sp.). Not Camatopsis rubida Alcock & Anderson, 1899 .

Type material. Holotype male (3.6 × 4.3 mm) (NNM-ZMA), Indonesia, Java, Kwandang Bay , Siboga Expedition , stn 114, 75 m.

Paratypes: 2 females (4.0 × 4.9 mm, 2.7 × 3.5 mm) (NNM-ZMA), collected with the holotype.

Other material examined. Indonesia. SIBOGA EXPEDITION : 1 male (3.8 × 4.6 mm) , 2 males (partially crushed) (NNM-ZMA), stn 116, west of Kwandang Bay entrance, 72 m, 07.1899 ; 1 male (3.4 × 4.0 mm) ( NNM- ZMA), stn 260, northwest of Kei Is. , 90 m, 0 7.1899.

Diagnosis. Carapace ( Fig. 8 G, H) subtrapezoidal, 1.0‒1.3 wider than long; front bilobed, with shallow to sometimes deep median cleft; anterolateral margins arcuate, carapace minutely granular with granules higher along lateral margins, without distinct lobes or teeth. Eye peduncle ( Fig. 23 F) filling orbit, short, slightly mobile; cornea reduced, with reduced pigmentation. Epistome ( Fig. 23 F) with wide, semicircular median lobe with deep median fissure, semicircular lateral margins. Third maxilliped merus subcircular, ischium subquadrate, about same length as merus. Proportionally short ambulatory legs ( Fig. 8 G). Chelipeds ( Figs. 8 G, H; 39G, H) subequal in length, slightly dissimilar in females, heteromorphic in males. Major chela of males ( Fig. 39 G) with thick propodus, cutting margins with small teeth, distal end of pollex overlapping dactylus. Minor chela of both sexes ( Fig. 39 H) with short teeth of about same size. Inner margin of cheliped carpus smooth. Fused thoracic sternites 1, 2 ( Fig. 69 A) triangular, proportionally narrow, short. Male pleon ( Fig. 69 B) with proportionally short telson. G1 ( Fig. 69 C‒E) stout, distal segment straight, tip directed upwards, with short spinules, distal segment flared, medially cleft. G2 ( Fig. 69 F) about 1/2 G1 length, straight, slender, distal segment short, straight. Female pleon ( Fig. 86 E) with lateral margins of somites strongly convex; telson proportionally short. Sterno-pleonal cavity moderately deep, vulvae far apart from each other.

Etymology. The species epithet minor alludes to the small size of adults.

Remarks. The recognition of this new species is necessary because it appears to mature at a much smaller adult size than in other Camatopsis species as well as having a characteristic G1 structure. Serène & Soh (1976: 23, fig. 21) recorded and figured the G1 of a small male specimen (4.5 × 5.0 mm) from Phuket in the Andaman Sea that they identified as “ Camatopsis rubida ”. The G1 is characteristic by being straight with the tip flared and with a median cleft. We have found the same G 1 in small specimens from the Indonesia Siboga material that we initially assumed belonged to young males with the structure expected to change with growth. Small specimens of C. rubida and C. leptomerus n. sp., however, at less than 4 or 5 mm in carapace width from Indonesia and Philippines already have the characteristic G1 structure of their respective species (e.g., Fig. 68 A, B), and as such, the differences observed with C. minor n. sp. cannot be attributed to growth. In addition, small females of C. minor n. sp. already have the pleon and pleopods fully developed. The smaller chela of C. minor n. sp., however, does not have the two upright, vertical teeth on the cutting margin of the pollex that is typical of adults of Camatopsis species. While the chelae of C. minor n. sp. show asymmetry, with one chela swollen and enlarged ( Fig. 39 G, H), indicating it is already mature, small specimens of other Camatopsis species of a similar size generally have both chelae similarly structured (e.g., Figs. 39 C, D). As such, we recognise a new species for this Indonesian material that was originally been identified by Tesch (1918) as “ Camatopsis rubida Form B ” (see discussion under C. rubida ). We also provisionally include Serène & Soh’s (1976) record from the Andaman Sea.

Distribution. Indonesia and questionably Andaman Sea. Depth: 72‒ 90 m.