Siderochinia aglaos, Yan & Lee & Forges & Ng, 2021

Yan, Bee, Lee, Forges, Bertrand Richer De & Ng, Peter K. L., 2021, The generic affinities of the Indo-West Pacific species assigned to Rochinia A. Milne-Edwards, 1875 (Crustacea: Brachyura: Majoidea: Epialtidae), Raffles Bulletin of Zoology 69, pp. 19-44 : 36

Siderochinia aglaos , new species

( Figs. 7D–F , 8D–F , 9K, L )

Rochinia kagoshimensis – Lee et al., 2017: 19, 20, 22 (in part), figs. 7C, 10D–F, 11G–J.

Material examined. Holotype: male (10.7 × 6.9 mm) (ZRC 2016.0549), stn CP4159, northwest of Dongsha , South China Sea, 20°45.92′N 116°41.11′E to 20°47.62′N 116°42.35′E, 221– 190 m, coll. ZHONGSHA 2015 Expedition, 30 July 2015.

Diagnosis. Small species. Carapace triangular, covered with tomentum, large tuft of long setae on mesogastric region. Pseudorostral spines relatively long, curved, diverging. Small round eyes. Supraorbital eave narrow, forming sharp distal angle. Small postorbital angle forming cavity protecting eye. Carapace with distinct spines: 2 long hepatic spines, pointed obliquely outwards; 1 short gastric spine surrounded by hooked setae; 1 strong thick cardiac spine with blunt squarish tip; 2 thick branchial spines long, pointing outward with rounded tips, proximal small spine on each branchial spine and pointing upwards; 1 intestinal spine on posterior margin of carapace. Long setae along lateral edge of carapace, between hepatic and branchial spines ( Fig. 7D ). Antennae shorter than pseudorostral spine. Basal antennal article wide, fused on carapace, rectangular with straight distal edge, sharp external distal angle. Distinct tubercle at base of basal antennal article. Epistome small. Pterygostomial region with 2 or 3 small granules on edge. Buccal frame squarish ( Fig. 7E ). Male cheliped short, propodus slightly inflated, fingers serrulate, carpus carinate, merus bearing swellings on border, covered by short setae. Ambulatory legs: P2 longest; on each leg, distal border of carpus and merus with stout setae; merus with several small bulbous setae; distal end of merus with blunt spine; dactylus slightly curved with sharp tip, proximal region covered with row of setae, 3 short spines on inner margin of distal third of dactylus of P5, weaker spines on ventral margin of P2–P4 dactylus ( Figs. 7D , 8F ). Male thoracic sternum anteriorly slightly depressed. Male pleon with triangular telson and 6 somites, widest at second and third ( Fig. 7E ). G1 with wide, flattened tip; slightly constricted in distal region near tip ( Fig. 9K, L ).

Etymology. The species name is derived from the Greek word, "aglaos", alluding to the word splendid. The name is used as a Latin noun in apposition.

Remarks. Lee et al. (2017) observed that there were some morphological differences between the holotype specimen of Siderochinia kagoshimensis , new combination, and their South China Sea specimen, but as they only had two specimens, they decided to treat both as conspecific at that time. Recently, both specimens were re-examined at length and more differences between the two were observed and are here treated as separate species. The South China Sea specimen is recognised as a separate species, S. aglaos , new species, distinct from S. kagoshimensis .

Siderochinia aglaos , new species, differs from S. kagoshimensis in having more widely diverging and outwardly curved pseudorostral spines ( Fig. 7D ) (vs. less divergent, straighter and more V-shaped, straight pseudorostral spines in S. kagoshimensis ; Fig. 7A ); the hepatic spines are directed laterally outwards ( Fig. 7D ) (vs. the hepatic spines directed slightly upwards in S. kagoshimensis ; Fig. 7A ); the branchial spines are directed upwards and prominently posteriorly, at an angle of almost 45° ( Figs. 7D , 8D, E ) (vs. the branchial spines directed more prominently upwards and less posteriorly in S. kagoshimensis ; Figs. 7A , 8A, B ); the cardiac spine gently tapers towards a subtruncate tip ( Figs. 7D , 8D ) (vs. cardiac spine with proximal and distal parts subequal in width, with the tip truncate in S. kagoshimensis ; Figs. 7A , 8A ); there is only one intestinal spine ( Figs. 7D , 8E ) (vs. with one small accessory spine at the top of the main intestinal spine in S. kagoshimensis ; Figs. 7A , 8B ); the male thoracic sternum is relatively less depressed anteriorly ( Fig. 7E ) (vs. male thoracic sternum more depressed anteriorly in S. kagoshimensis , new combination; Fig. 7B ); and the subdistal part of the G1 is relatively less constricted with the tip proportionately shorter and more rounded ( Fig. 9K, L ) (vs. subdistal part of G1 more distinctly constricted with the tip longer and sharper in S. kagoshimensis ; Fig. 9G, H ).

Distribution. Only known from South China Sea ( Lee et al., 2017).

Figures

Fig. 7. A–C, Siderochinia kagoshimensis (Rathbun, 1932) new combination, holotype male (11.2 × 6.8 mm) (USNM 48253), Japan; D–F, S. aglaos, new species, holotype male (10.7 × 6.9 mm) (ZRC 2016.0549), South China Sea (after Lee et al., 2017: fig. 10D–F). A, D, overall dorsal view; B, E, overall ventral view; C, F, lateral view of carapace.

Fig. 8. A–C, Siderochinia kagoshimensis (Rathbun, 1932) new combination, holotype male (11.2 × 6.8 mm) (USNM 48253), Japan; D–F, S. aglaos, new species, holotype male (10.7 × 6.9 mm) (ZRC 2016.0549), South China Sea. A, D, side view of cardiac spine; B, E, dorsal view of intestinal spine along lateral carapace margin; C, F, dorsal view of P5.

Fig. 9. Left G1 and G2. A, B, Laubierinia globulifera (Wood-Mason, in Wood-Mason & Alcock, 1891) new combination, male (9.2 × 6.0 mm) (AM P.34652), Indonesia; C, D, Oxypleurodon fultoni (Grant, 1905) new combination, holotype male (8.2 × 5.1 mm) (AM G.5427), Australia; E, F, Pugettia vesicularis (Rathbun, 1907) new combination, holotype male (14.6 × 10.6 mm) (USNM32860), Galapagos; G–J, Siderochinia kagoshimensis (Rathbun, 1932) new combination, holotype male (11.2 × 6.8 mm) (USNM 48253), Japan (after Lee et al., 2017: fig. 11E, F); K, L, S. aglaos, new species, holotype male (10.7 × 6.9 mm) (ZRC 2016.0549), South China Sea (after Lee et al., 2017: fig. 11G–J). A, C, E, G, K, ventral view; B, D, F, H, L, dorsal view; I, ventral view of G2; J, dorsal view of G2. Scale bar = 1 mm.