Samadinia hakuhoae, Arzivian & Alrubaie & Yang & Lin & Zhang & Leong, 2022

Arzivian, Arteen, Alrubaie, Ahmad, Yang, Jessica, Lin, Huiyu, Zhang, Eva & Leong, Rupert, 2022, Crabs (Crustacea, Decapoda) from the Seas of East and Southeast Asia Collected by the RV Hakuhō Maru (KH- 72 - 1 Cruise) 4. South China Sea, Bulletin of the National Museum of Nature and Science. Series A, Zoology 48 (4), pp. 147-191 : 160-164

publication ID	https://doi.org/ 10.50826/bnmnszool.48.4_147
persistent identifier	https://treatment.plazi.org/id/5F30F95F-FFF3-9023-FF66-FE04FB735851
treatment provided by	Felipe
scientific name	Samadinia hakuhoae
status	sp. nov.

Treatment

Samadinia hakuhoae View in CoL sp. nov.

( Figs. 5–6 View Fig View Fig , 7D–G View Fig )

urn:lsid:zoobank.org:act:19A47CD2-4868-4AD0-B160-CA19FC43A550

Material examined. RV Hakuhō Maru KH-72-1 cruise, sta. 54, Ə (CB 10.7 mm excluding branchial spines, PCL 16.3 mm), holotype, NSMT-Cr 30915; 1Ə (8.8× 13.6 mm), 1 8 (10.5× 15.9 mm), paratypes, NSMT-Cr 30916; 1 ovig.8 (10.8× 16.3 mm), paratype, NSMT-Cr 30951; 1 8(8.3×13.0 mm), paratype, NSMT-Cr 30917; 1 8(12.8× 18.9 mm), paratype, NSMTCr 30918.

Description of holotype. Carapace ( Fig. 5A View Fig ) pyriform, entirely covered with tomentum (mostly abraded); surface smooth. Gastric region weakly elevated, medially with obtusely pointed conical mesogastric tubercle between low, rounded, protogastric protuberance on each side; cardiac region weakly elevated, with large conical tubercle. Branchial region with 3 distinct, short, conical tubercles, prebranchial region slightly elevated, with 2 tubercles obliquely (mesial one larger than lateral one), metabranchial tubercle shorter than cardiac tubercle; epibranchial spine long, 1.1 times as long as CB excluding spines, slender, directing laterally and obliquely upward ( Fig. 5B–C View Fig ). Intestinal region low, medially with short, dorsally directed spine on medially convex, posterior carapace margin. Pterygostomian region ( Fig. 6D View Fig ) not markedly inflated, with 4 low tubercles on gently ridged, pleural suture.

Pseudorostral spines ( Fig. 5A, D View Fig ) slender, 0.7×PCL, widely separated from bases, weakly outcurved laterally. Supraorbital eave strong, anteriorly produced into subacute, dorsolaterally directed preorbital lobe, with smooth subsurface; postorbital lobe separated from eave by keyholeshaped orbital hiatus; postorbital lobe smooth, compressed laterally (=postorbital plate), subcircular, forming plate-like lateral wall of incomplete orbit. Hepatic margin laterally with dorsally directed elongate lobe (=hepatic plate), incurved distally, lateral surface flattened, smooth, ovoid, with acuminate tip, separated from postorbital plate deep sulcus.

Basal antennal article ( Fig. 6D View Fig ) smooth, surface smooth, distolateral angle produced into short tooth, lateral margin entire, straight, proximally with small acute tubercle sealed by laterally produced, anterolateral angle of buccal cavity ( Fig. 7D View Fig ). Penultimate article slender, length two-thirds that of ultimate peduncular article. Flagellum not reaching tip of pseudorostral spines.

Cheliped ( Figs. 5A–B View Fig , 6D View Fig ) with few setae and sparse tomentum on lower margin of merus and inner margin of carpus; merus trigonal in crosssection, margins sharply carinate for entire length; dorsal carina irregularly dentate in proximal half, distally with strong, anteriorly directed tooth ( Fig. 5A–B View Fig ); ventromesial carina entire ( Fig. 5A View Fig ); ventrolateral carina tri-dentate ( Fig. 5B View Fig ). Carpus strongly crested on dorsal, mesial, lateral margins. Chela moderately compressed, tapering toward fingertips; palm sharply carinate on upper and lower margins; fingers almost as long as palm, slightly curved distally, occlusal margins weakly dentate, without any prominent tooth subproximally, with slight gap when closed.

Ambulatory legs ( Fig. 5A View Fig ) slender, tomentose. Merus cylindrical, almost one-third length of PCL in P5. Carpus simple. Propodus subcylindrical. Dactylus slender, faintly falcate, with 0, 4–5 denticles on flexor surface in P2, P3, respectively; weakly falcate, with 5 or 6 low, rounded tubercles on flexor surfaces in P4, 5, respectively.

Pleon ( Fig. 6D View Fig ) with six somites and triangular telson; pleomeres 3–5 medially ridged; pleomere 6 with large tubercles on both sides, short, medial tubercle anteriorly.

G1 ( Fig. 7D–F View Fig ) shaft straight, not markedly different from that of S. kotakae ( Takeda, 2001) . G2 ( Fig. 7G View Fig ) short, simple.

Notes on paratypes. Erect tubercles on carapace dorsal surface shorter, less distinct in females than in males ( Fig. 6B View Fig ), reduced in smaller specimens ( Fig. 6C View Fig ). Pseudorostrum not markedly shorter in females, but less divergent anteriorly when compared with males ( Fig. 6A View Fig ). Relative length of epibranchial spines against CW 0.7–0.9 (N=4), smaller than in males (1.1, N=2) ( Fig. 6A View Fig ). Postorbital, hepatic plates continuous, but the degree of fusion somewhat variable probably sexually and/or ontogenetically ( Fig. 6B–C View Fig ). Chela slender, palm not so sharply carinate on both upper and lower margins, fingers simply dentate, not gaping when closed in females ( Fig. 6E View Fig ). Female pleon covered with a thick tomentum in both adolescent and fully grown specimens ( Fig. 6E View Fig ).

Etymology. Named after the RV Hakuhō Maru.

Remarks. The genus Samadinia was established by Ng and Richer de Forges (2013). Lee et al. (2021) transferred 26 species previously placed in Rochinia to Samadinia , and subsequently, Richer de Forges et al. (2021) recorded four additional species; S. livermorii (Wood-Mason, in Wood-Mason and Alcock, 1891) was transferred from Scyramathia A. Milne-Edwards, 1880 , and three new species, S. jefrii , S. taylorae , and S. yoyoae were described from Indonesian waters. Prior to the present study, Samadinia included 30 species, all from Indo-Pacific waters.

Samadinia hakuhoae View in CoL sp. nov. apparently belongs to the riversandersoni View in CoL group suggested by Griffin and Tranter (1986: 365) and Ho et al. (2004), which also includes S. kotakae ( Takeda, 2001) View in CoL , S. riversandersoni ( Alcock, 1895) View in CoL , and S. galatheae ( Griffin and Tranter, 1986) ( Lee et al., 2021) . However, the combination of a distinct gap between the laterally flattened postorbital and hepatic lobes, weakly upturned hepatic plate, short but distinct seven dorsal spines (=erect tubercles in Ho et al., 2004), and noticeably longer lateral spines differentiate Samadinia hakuhoae View in CoL sp. nov. from the known congeners.

Samadinia hakuhoae View in CoL sp. nov. is closest to S. kotakae View in CoL known from Japan and the Philippines at depths of 685–1,060 m ( Takeda, 2001; Ho et al., 2004; Lee et al., 2017). In addition to the aforementioned characters, however, the following characters differentiate the two species: 1) the hepatic plate is less upturned dorsally and acuminate at the tip (tapering toward a rounded apex in S. kotakae View in CoL ); 2) the pterygostomian region bears three large tubercles (smooth in S. kotakae View in CoL ); 3) the dorsal spines on the branchial region are more prominent than in S. kotakae View in CoL , in which they are replaced by acute tubercles; 4) in males, the epibranchial spines are longer than in S. kotakae View in CoL (1.1 times CW in S. hakuhoae View in CoL sp. nov. vs. 0.48 times in S. kotakae View in CoL ); 5) the intestinal spine is moderately long and directed somewhat dorsally in the new species, but it is very short and obscured by tomentum in S. kotakae View in CoL ; 6) in S. hakuhoae View in CoL sp. nov., the P5 dactylus is 1/3 length PCL, but almost half PCL in S. kotakae View in CoL ; 7) the G1 of S. hakuhoae View in CoL is not markedly different from that of S. kotakae View in CoL in general outline, but the complex folds near the aperture are strongly curved at the distal part in contrast to the figure given by Richer de Forges and Ng (2013, fig. 81J).

The present new species shares the laterally directed hepatic plates with Samadinia riversandersoni View in CoL widely distributed in the Indo-West Pacific including the South China Sea, 428– 1362 m depth. However, the dorsal spines are seven and much shorter in S. hakuhoae View in CoL sp. nov. contrary to 15 very long dorsal spines in S. riversandersoni View in CoL . The postorbital plate is separated from the hepatic plate in the new species ( Figs. 5D View Fig , 6B–C View Fig ), but they are continuous in S. river- sandesoni. Yaldwyn and Dawson (1976, figs. 6–8) showed the strong spination of the carapace in the specimens from New Zealand waters, 234– 635 m in depth.

The following three species shares with S. hakuhoae sp. nov. the postorbital and strongly upturned hepatic plates that are distinctly separated by a distinct gap: S. galatheae (type locality: off Natal, 535–610 m), S. sibogae (Ceram Sea, 924 m), and S. strangeri ( Serène and Lohavanijaya, 1973) (South China Sea, 479 m). However, S. galatheae has more rounded carapace with less divergent pseudorostral spines and its postorbital-hepatic plates are fused to one another ( Griffin and Tranter, 1986, fig. 11). The posteriorly-produced intestinal spine is very long (see Richer de Forges and Poore, 2008, fig. 2C). In S. strangeri , the lateral branchial spines are short and similar to the other dorsal spines in length ( Lee et al., 2017, fig. 9). In these three species, the G1 form is also different from that of S. hakuhoe sp. nov. ( Fig. 7A–C View Fig vs. Lee et al., 2017, figs. 9, 11A–D).

Distribution. Known only from the type locality, South China Sea, 760–777 m depth.

Kingdom	Animalia
Phylum	Arthropoda
Class	Malacostraca
Order	Decapoda
Family	Epialtidae
Genus	Samadinia